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NikonHank Silver Member Nikonian since 14th Jan 2009Thu 11-Nov-10 06:54 PM
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"D7000 & Diffraction"


Howell, US
          

Hello fellow Nikonians:

Bear with me here as I'm no expert on diffraction.

I had corresponded with a professional photgrapher who happened to mentioned the D7000's high pixel count, on a DX sized sensor, may cause diffraction to occur at f/8 or lower. This would affect DOV and impact macro and landscape shooting.

Has anyone had diffraction issues with lenses on the D7000? May one conclude the 12 mp DX bodies limit diffraction better?

Thanks for your thoughts.

Hank

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km6xz Moderator
11th Nov 2010
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MstrBones Silver Member
12th Nov 2010
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km6xz Moderator
12th Nov 2010
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NikonHank Silver Member
12th Nov 2010
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Len Shepherd Gold Member
12th Nov 2010
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briantilley Moderator
12th Nov 2010
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Len Shepherd Gold Member
12th Nov 2010
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elec164 Silver Member
12th Nov 2010
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Len Shepherd Gold Member
19th Nov 2010
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AreBee
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km6xz Moderator Awarded for his in-depth knowledge in various areas, including Portraits and Urban Photography Nikonian since 22nd Jan 2009Thu 11-Nov-10 08:58 PM
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#1. "RE: D7000 & Diffraction"
In response to Reply # 0


St Petersburg, RU
          

There is a lot of confusion and misinformation on the web...naturally but for normal viewing(not 100% crops) the visibility of deffraction induced loss of detail is swamped by a lot of factors that are of greater impact such as tripod flexibility, mirror slap etc.
Here is a good tutorial on the subject:
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm
Stan
St Petersburg Russia

Visit my Nikonians gallery.

  

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MstrBones Silver Member Nikonian since 06th Dec 2005Fri 12-Nov-10 12:25 AM
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#2. "RE: D7000 & Diffraction"
In response to Reply # 1


AW
          

>There is a lot of confusion and misinformation on the
>web...naturally but for normal viewing(not 100% crops) the
>visibility of deffraction induced loss of detail is swamped by
>a lot of factors that are of greater impact such as tripod
>flexibility, mirror slap etc.
>Here is a good tutorial on the subject:
>http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm



Actually, that's the article that many reference when talking about high megapixel sensors having significantly more diffraction at smaller apertures than lower resolution sensors.

Mirror slap is relatively insignificant for most shots, btw. It mostly affects landscapers at shutter speeds in a specific range of speeds. Tripod vibration is pretty insignificant also if one uses proper damping techniques for the tripod itself.


""

  

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km6xz Moderator Awarded for his in-depth knowledge in various areas, including Portraits and Urban Photography Nikonian since 22nd Jan 2009Fri 12-Nov-10 04:44 AM
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#4. "RE: D7000 & Diffraction"
In response to Reply # 2


St Petersburg, RU
          

The user induced softening contributors seem to be the most important factors. Tripod vibration and slap should only be a problem with specific user technique faults but viewing many many posted images, apparently user technique IS what makes the majority of "soft" images soft.

With good technique, some of the posted images of the D7000 appear to be as sharp as anything out there. There are also a lot of images posted with the same equipment that are poor. That's why I said diffraction is a less significant factor than the current buzz and belief on the internet holds, than just plain poor work habits, and user choices like critical shutter speed zones for lenses. From what I see, diffraction does not cause the problem.

Stan
St Petersburg Russia

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NikonHank Silver Member Nikonian since 14th Jan 2009Fri 12-Nov-10 02:28 AM
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#3. "RE: D7000 & Diffraction"
In response to Reply # 1


Howell, US
          

Hi Stan:

Thank you for the link and your opinion. By the way, I really enjoy reading your posts.

Have a good evening,

Hank

Visit my Nikonians gallery.

  

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Len Shepherd Gold Member Nikonian since 09th Mar 2003Fri 12-Nov-10 08:17 AM
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#5. "RE: There is a lot of garbage on the web."
In response to Reply # 0
Fri 12-Nov-10 08:27 AM by Len Shepherd

Yorkshire, GB
          

Diffraction has NOTHING to do with pixel density - it occurs at the aperture in the lens - amen.
It is influenced by physical size of the aperture and the circle of confusion - but nothing else. The size of the COC varies with format, which is why the diffraction effect varies with format.
DX shows diffraction about 0.66 stops wider than FX, but DX has (for the same viewfinder crop) has just over 1 stop more DOF than FX. This means you can get slightly more dof at optimum aperture for the format with DX than FX.
It is rare for a fast lens to have usefully better optical quality at f2 than at f22, or at f4 than at f16 - so either you do not use fast lenses at fast apertures (which defeats the object of Nikon making them ) - or you CAN shoot at smaller apertures than the diffraction limit.
Edit http://www.ephotozine.com/article/Nikon-AFS-Nikkor-200mm-f2G-ED-VRII-15047 is useful as a diffraction discussion point.
According to "diffraction web hype" shooting at a smaller aperture than the diffraction limit means waste paper bin rubbish.
The performance is near identical at f2 and f22, and also at f4 and f16.
The f16 performance mid way between good and excellent is fine for a 24 inch wide print from a D3x So who is afraid of the big bad diffraction wolf that, if you make large prints, turns out to have no teeth?
Mythical web stories repeated by enough web readers often enough become accepted by some as true - even though mythical stories are not true

Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.

Len Shepherd

  

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briantilley Moderator Deep knowledge of bodies and lens; high level photography skills Nikonian since 26th Jan 2003Fri 12-Nov-10 09:11 AM
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#6. "RE: There is a lot of garbage on the web."
In response to Reply # 5
Fri 12-Nov-10 09:12 AM by briantilley

Paignton, GB
          


Hi, Len.

I think this topic last came up in our Nikkor Lenses Forum, in which thread this link was provided. It's the same one that Stan linked to above.

The tutorial contains a useful calculator to determine whether images using a given camera type and lens aperture will be diffraction-limited. As well as sensor size and lens aperture (and print size and viewing distance), it does include pixel count (or density) as one of the variables.

The calculator indicates that, with other values kept constant, a 10MP DX camera (like the D200) will become diffraction limited between f/11 and f/13, whereas a 17MP DX camera (like the D7000) will become diffraction limited earlier, between f/8 and f/11.

Are you saying that the tutorial and calculator are wrong?

Either way, I agree with you and others that the practical impact of lens diffraction tends to be overblown, and we worry about it more than we should

Brian
Welsh Nikonian

  

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Len Shepherd Gold Member Nikonian since 09th Mar 2003Fri 12-Nov-10 10:46 AM
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#7. "RE: There is a lot of garbage on the web."
In response to Reply # 6


Yorkshire, GB
          

>Hi, Len.
>I think this topic last came up in our Nikkor Lenses Forum, in which thread the :www.cambridgeincolour.com/tutorials/diffraction-photography.htm|was provided. It's the same one that Stan linked to above.

The tutorial is, unfortunately inaccurate
That it is on the web has got nothing to do with whether it is right or wrong.
My main point is the laws of physics have not changed and smaller grain size in film or higher pixel density on sensors never have been a factor in the laws diffraction.
Digressing as sensor technology advances pixel well depth reduces and micro lens size increases relative to pixel pitch so whatever goes on at the sensor surface is a moving playing field.
Although there are around 4200 pixels on the long dimension of a 12 MP there are only 1050 red sensors and 1050 blue sensors, which works out at just 28 red and 28 blue sensors per millimeter of sensor length or width.
In theory it takes 4 pixels 1 red, 1 blue and 2 green) to determine 1 colour detail. Bayer type sensors usually work by comparing detail at around 32 different pixels sites, "center weighted", and apply a code to each pixel site. The camera processing engine works out the colour, and much higher resolution than is possible from just 28 red or 28 blue pixels per millimeter. One way this is achieved is using pinned photo diodes (invented in 1980) to extremely efficiently convert incoming light into electrons.
There is a lot more to the quality of digital image output than pixel pitch in isolation.

Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.

Len Shepherd

  

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elec164 Silver Member Nikonian since 15th Jan 2009Fri 12-Nov-10 11:41 AM
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#9. "RE: There is a lot of garbage on the web."
In response to Reply # 7
Fri 12-Nov-10 12:50 PM by elec164

US
          

>>Hi, Len.
>>I think this topic last came up in our Nikkor Lenses
>Forum, in which thread the
>:www.cambridgeincolour.com/tutorials/diffraction-photography.htm|was
>provided. It's the same one that Stan linked to above.
>
>The tutorial is, unfortunately inaccurate

I don’t believe the tutorial is inaccurate, but that you are just miss interrupting the purpose of the “set CoC based on pixels’ check box.

Quote:
“The “set circle of confusion based on pixels’ checkbox is intended to give you an indication of when diffraction will become visible when viewing you digital image at 100% on a computer screen. Understand that the diffraction limit is only a rough limit; there is actually a gradual transition between when diffraction limit is and is not visible.”


I take that to mean that it is only for a quick way of changing the print size and viewing distance based upon 100% screen viewing and not when diffraction for a particular print size and viewing distance is considered. You may argue that his metric for that setting is inaccurate, but I believe your saying the tutorial is as a whole is inaccurate is a misunderstanding of why the tick box is included.

Pete

Edited to elaborate:

To make myself more clear, monitors only show images on a pixel per pixel basis. So a full resolution 10MP image will show more of a percentage of the image on screen than a 16MP image will at 100% view. So he included the tick box to attempt to provide an easy way to account for the difference in the amount shown when viewing on monitor at 100% for a given pixel density. It has nothing to do with the micron size of the sensel but the pixel dimensions of the image. Where I feel it goes awry is that to include that he has to assume a specific screen resolution with the video adapter set to display that native resolution of the monitor. If you set the adapter to display less than the native resolution or one person has a screen with a much higher native resolution than another, then the tick box info would be inaccurate. Granted his inclusion is close enough for a hand grenade, but if you want sniper rifle accuracy with that calculator then instead of using the tick box you would just change the print size dimension at the default 25cm viewing distance depending on the resolution of the sensor and native resolution of your monitor. For instance an image from my 10MP D80 displayed on my 86 PPI monitor would be akin to viewing a print with a maximum size of 40 inch at a 18 inch viewing distance instead of the normal viewing distance of about 40 to 50 inches. So in that viewing distance scenario the CoC would need to be much smaller for the shorter than normal viewing distance; or stated another way is that diffraction seems more apparent with the reduced viewing distance. At least I hope I got all that correct.

Pete

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Len Shepherd Gold Member Nikonian since 09th Mar 2003Fri 19-Nov-10 06:34 PM
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#39. "RE: There is a lot of garbage on the web."
In response to Reply # 9


Yorkshire, GB
          

tutorial is, unfortunately inaccurate
>I don’t believe the tutorial is inaccurate, but that you are just miss interrupting the purpose of the “set COC based on
>pixels’ check box.
Do you believe pigs can fly?
I am sure somewhere on the web some-one says they do
>Quote:
>“The “set circle of confusion based on pixels’ checkbox is
>intended to give you an indication of when diffraction will
>become visible when viewing you digital image at 100% on a
>computer screen.
STOP
A different COC is needed to that assumed in dof field calculations when viewing at 100%.
The starting point for dof assumptions is a 10 inch wide print.
Viewing at 100% from 12 MP (about 40 wide equivalent) if you shot at f8 you get around f2 dof equivalent viewing at 12-15 inches.
Viewing at 100% from 16 MP changes f8 dof to f1.4 equivalent.
***
Viewing at 100% is usually "inferior" to real world photography in the sense few buy high resolution monitors (because they are very expensive) and also because 200-300 pixels per inch equivalent is needed for a decent print - and most "affordable" monitors display less than 100 pixels an inch at 100%.
Sorry - the only relevance of viewing at 100% as a precursor to making a print is to check for edge halos when sharpening.

Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.

Len Shepherd

  

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AreBee Registered since 27th Apr 2008Fri 12-Nov-10 11:30 AM
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#8. "RE: There is a lot of garbage on the web."
In response to Reply # 5
Fri 12-Nov-10 11:33 AM by AreBee

Inverness, GB
          

Len,

>http://www.ephotozine.com/article/Nikon-AFS-Nikkor-200mm-f2G-ED-VRII-15047 is useful as a diffraction discussion point. According to "diffraction web hype" shooting at a smaller aperture than the diffraction limit means waste paper bin rubbish. The performance is near identical at f2 and f22, and also at f4 and f16.<

Yet targets shot with the (old) 200mm f/2 here (near the bottom of the page) demonstates that f/2 is clearly not comparable to f/22, with the former visibly better than the latter.

Or am I missing something?

EDIT: Oops, I see now that the first target is actually for f/2.8. Sorry!

Rob
www.robbuckle.co.uk

  

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NikonHank Silver Member Nikonian since 14th Jan 2009Fri 12-Nov-10 02:17 PM
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#10. "RE: There is a lot of garbage on the web."
In response to Reply # 5


Howell, US
          

Hi Len:

Thank you for the informative explanation and the link.

Have a great day,

Hank

Visit my Nikonians gallery.

  

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NikonHank Silver Member Nikonian since 14th Jan 2009Fri 12-Nov-10 03:34 PM
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#11. "RE: There is a lot of garbage on the web."
In response to Reply # 5


Howell, US
          

Hi Len:

I just found this article which includes information on "diffraction broadening":

http://www.luminous-landscape.com/essays/Equivalent-Lenses.shtml

It's pretty technical and while I had two courses in college physics (back in the day), it increased my confusion (pun intended) on whether the D7000 will be more diffraction limited than a 12 mp DX camera.

Have a good day!

Hank

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blw Moderator Awarded for his high level of expertise in various areas Nikonian since 18th Jun 2004Fri 12-Nov-10 03:55 PM
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#12. "RE: There is a lot of garbage on the web."
In response to Reply # 11


Richmond, US
          

At the end of the day, what counts is what you print and hang on the wall. If you're confused about this - and I'm not surprised if anyone is - just go shoot some controlled subject under optimal conditions and compare. See if you like the results.

As I've written in other threads, probably to the point of boring everybody to death, I've done the experiment myself and as a result I'm quite willing to stop down to f/16, f/22 or even f/45 on most lenses if that's what will get me the DOF that makes the image. See this thread where I show just how "badly damaged" my macro shots are at f/22. An 11x16 print of this horribly damaged shot just sold for $390 at an auction, so there is at least one other crazed individual on the planet who thinks it looks OK.

_____
Brian... a bicoastal Nikonian and Team Member

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NikonHank Silver Member Nikonian since 14th Jan 2009Fri 12-Nov-10 04:28 PM
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#13. "RE: There is a lot of garbage on the web."
In response to Reply # 12


Howell, US
          

Hi Brian:

Thanks for responding. Your point is well made and the proof is in the photo. That's a great shot!

Did you take that picture with a D3? If so, do you think the image quality would be compromised if you used a D7000 instead? I know your answer will be theorectical since you do not shoot with a D7000.

All the Best,

Hank

Visit my Nikonians gallery.

  

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blw Moderator Awarded for his high level of expertise in various areas Nikonian since 18th Jun 2004Fri 12-Nov-10 05:23 PM
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#15. "RE: There is a lot of garbage on the web."
In response to Reply # 13


Richmond, US
          

I think that was shot on a D2x, not a D3. Even if it was the D3, I think that yes, the IQ would have been "compromised" as I understand the diffraction effect. (Note that it's entirely possible that I don't understand the diffraction effect very well. You can see what my basic attitude about it is, so it's not as if I've spent a lot of time studying the physics.) On the other hand, if shot on a D7000, I think that the IQ would also have been *improved* in some regards, as it's clearly also true that the denser sensor as well as (likely) a weaker antialiaasing filter would contribute to greater fundamental resolution, and at least in my mind it's an open question as to whether or not the net result would be better or worse. If I had to guess, I'd say probably it would be better.

One reason that I don't really know is that it just doesn't matter to me. Suppose the D7000 image would have been slightly better or slightly worse. (I can guarantee that it won't be drastically better or worse.) If I make an 11x16 print, put it in a 16x22 inch frame and put it on the wall, who's going to know if it would have been slightly better or worse if I'd have used a different camera? I can't even tell from looking at the image itself which of my own cameras that I used. (I can be pretty sure it wasn't the D100, mostly because of that camera's antialiasing filter.) Suppose I had used a Sigma 150/f2.8 instead? Or perhaps a 300/f4 AFS with extension tubes? It surely would have looked different if I had shot it with my F100 loaded with Velvia. And I bet the biggest difference of all would have come from shooting it with a ring flash instead of my SB-800 hand-held on a flash cord.

_____
Brian... a bicoastal Nikonian and Team Member

My gallery is online. Comments and critique welcomed any time!

  

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blw Moderator Awarded for his high level of expertise in various areas Nikonian since 18th Jun 2004Fri 12-Nov-10 06:07 PM
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#16. "RE: There is a lot of garbage on the web."
In response to Reply # 15


Richmond, US
          

Well, no, it wasn't on the D2x, it was the D3. I have several of these and I'd gotten confused as to which shoot it was from. I guess the message here is that I can't tell the difference very easily myself. I do have some other shots of the same species shot with the D2x and both the 200/f4 Micro and the Tamron 90/f2.8 Macro, and many of them are shot stopped down.

_____
Brian... a bicoastal Nikonian and Team Member

My gallery is online. Comments and critique welcomed any time!

  

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NikonHank Silver Member Nikonian since 14th Jan 2009Fri 12-Nov-10 09:26 PM
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#17. "RE: There is a lot of garbage on the web."
In response to Reply # 15


Howell, US
          

Hi Brian:

Thank you for taking the time to research what camera you used and the explanation of the D7000's advantages related to this issue.

Do you think diffraction may have effected the print quality if the print was larger, say 24"x 36"?

Have a good evening,

Hank

Visit my Nikonians gallery.

  

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blw Moderator Awarded for his high level of expertise in various areas Nikonian since 18th Jun 2004Sat 13-Nov-10 12:09 AM
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#19. "RE: There is a lot of garbage on the web."
In response to Reply # 17


Richmond, US
          

Probably diffraction IS degrading the image quality of all of these shots. The point is that it probably doesn't matter unless you're going to go compare. Ie if I go take that shot of the butterfly and make a 24x36 print from it, and I go take another shot of the same butterfly... oops, I didn't do that. OK if I go take a shot of another butterfly, one at f/22 and another one at f/8, and then print them both at 24x36, yes of course you will see the difference. One of them will have a LOT less DOF than the other. And, if you get over that difference, you will probably be able to see that one of them is somewhat sharper, too - the one without the DOF. You'd have to be looking IN the (smaller) in-focus area to compare, and you'd have to be mentally "masking out" the out-of-focus areas, because they will make the one with less DOF look soft, even though it's actually sharper. IF you do all that mental gymnastics, you will see that diffraction really is real - note that I didn't claim anywhere that it isn't real. But until you see the side-by-side, it doesn't really matter, because with good technique (or luck) you can get a quite sharp result even with diffraction interfering. Whether or not another hypothetically equivalent image might have been better is close to irrelevant if what you got is good enough.

In this case, I was lucky enough to get everything still enough (or any motion hidden enough, by using a flash), I used a top-caliber lens (200/f4 Micro) and mounted it all on a top-caliber tripod and head, so that I got a quite sharp result with appropriate DOF. That last part is crucial: I could easily have simply dialed back to f/8 to get a sharper image, but it either didn't cross my mind, or more likely it did and I did a DOF preview to discover that it was much less of a composition at f/8 than at f/22.

Whether I used a D3, a D7000 or 35mm film really isn't even the prime consideration.

----

Actually a DX body attempting to make precisely the same composition probably has a mild advantage over the D3 here: because for the same framing, the DX body yields roughly one additional stop of DOF. (Because for the same framing, you'd be 50% further away, ergo more DOF.) Since there's inherently more DOF, you need to stop down one less stop than on FX, thus potentially avoiding a little of the diffraction problem.

----

I should mention that I make a fair number of 24x36" prints, and by the time I am to the stage of making prints, I pretty much don't pay attention to shooting parameters, etc. I use the whole range of apertures on most of my lenses, so I'd assume that the prints are from a similar range of apertures. (There are some lenses that really perform pretty poorly when stopped down - the 35/f1.4 AIS is one of them - so I don't go there on those lenses. On the other hand, the 85/f2.8 PC looks pretty good at f/45, so I do use that.)

_____
Brian... a bicoastal Nikonian and Team Member

My gallery is online. Comments and critique welcomed any time!

  

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NikonHank Silver Member Nikonian since 14th Jan 2009Sat 13-Nov-10 02:20 AM
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#20. "RE: There is a lot of garbage on the web."
In response to Reply # 19


Howell, US
          

Hi Brian:

Thank you very much for this excellent, practical explanation. I learned a lot about diffraction in this post and I thank you for sharing your knowledge and experience.

Have a good night and a great weekend!

All the Best,

Hank

Visit my Nikonians gallery.

  

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elec164 Silver Member Nikonian since 15th Jan 2009Fri 12-Nov-10 04:40 PM
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#14. "RE: There is a lot of garbage on the web."
In response to Reply # 12


US
          

>so there is at
>least one other crazed individual on the planet who thinks it
>looks OK.

LOL, I like that remark!! And I fully agree that DOF can trump diffraction in most circumstances.

I think the confusion resides in the fact that the CoC metric is used when discussing both and while related are separate.

Someone correct me if I’m wrong, but in trying to sort it all out and keep it straight in my head I say to myself that diffraction limits the systems resolvability; while DOF determines how much of the image field appears in focus or apparently sharp. If the added DOF enhances the image more than the slight loss of fine detail due to diffraction, then I would have no problem stopping down to f/32 or beyond.

In the end I believe it’s like both Brian’s either said or imply in that this issue is often over thought and over considered. And as Len says the laws of physics are set, and diffraction seems to not be dependent on particle or sensel size. And the complexity of the Bayer array makes things even more confusing. For instance when pixel peeping the image I supplied in my hot pixel thread (really is a stuck sensel) it appears that that one stuck sensel impacted about 25 pixels.

Pete

Pete

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NikonHank Silver Member Nikonian since 14th Jan 2009Fri 12-Nov-10 09:29 PM
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#18. "RE: There is a lot of garbage on the web."
In response to Reply # 14


Howell, US
          

Hi Pete:

Thank you for the response.

I also want to thank everyone who has replied. This is a confusing subject but you've all managed to shed some light on this!

All the Best,


Hank

Visit my Nikonians gallery.

  

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TomCurious Registered since 03rd Jan 2007Sat 13-Nov-10 10:57 PM
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#24. "RE: There is a lot of garbage on the web."
In response to Reply # 5


Bay Area, US
          

>Diffraction has NOTHING to do with pixel density -

Wrong.

>it occurs at the aperture in the lens - amen.

Right.


The same diffraction (same lens, aperture, etc) projected onto a high pixel density sensor will be more obvious than on a low pixel density sensor, when viewing both images at 100%. Or to put it differently, diffraction (like many other aberrations) becomes more obvious when magnifying the image more. It's very simple.

Tom
Bay Area Nikonian


http://www.tkphoto.me/

  

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visionguru Registered since 03rd Nov 2008Mon 15-Nov-10 03:31 PM
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#25. "RE: There is a lot of garbage on the web."
In response to Reply # 24


Chicago, US
          

>>Diffraction has NOTHING to do with pixel density -
>
>Wrong.
>..................
>The same diffraction (same lens, aperture, etc) projected
>onto a high pixel density sensor will be more obvious than on
>a low pixel density sensor, when viewing both images at 100%.
>Or to put it differently, diffraction (like many other
>aberrations) becomes more obvious when magnifying the image
>more. It's very simple.
>
>
Sensor's sole responsibility is to record information as accurately as possible, be it diffraction pattern or not. You can always reduce resolution to avoid seeing things you don't want to, but you cannot increase resolution from low resoltion hoping to get more details. Diffraction is there regardless of the sensor resolution. It indeed has nothing to do with pixel density.

  

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briantilley Moderator Deep knowledge of bodies and lens; high level photography skills Nikonian since 26th Jan 2003Mon 15-Nov-10 04:12 PM
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#26. "RE: There is a lot of garbage on the web."
In response to Reply # 25
Mon 15-Nov-10 04:15 PM by briantilley

Paignton, GB
          

>Diffraction is there regardless of the sensor resolution.
>It indeed has nothing to do with pixel density.

Well, I'm still with Tom

I think we are all agreed that diffraction is an effect caused by the lens, but the degree to which diffraction affects an image depends on how that image is viewed. A greater degree of enlargement, or a reduction in the viewing distance, increases the visible effect of diffraction. It's like DEpth of Field - we often say that such-and-such a lens has so many inches DoF, forgetting that the actual figure depends on print size and viewing distance.

As pointed out in the article that a few of us have linked to, when you're viewing two images on-screen at 100% (or any other given percentage), one from a 10MP DX camera and one from a 17MP camera, you'll be seeing a smaller portion of the 17MP image. That's greater enlargement, so diffraction effects will become visible at a larger aperture. If you're printing same-size images from the two cameras, or viewing the whole images on screen, they will display the same diffraction effects.

None of this changes my belief that we worry too much about diffraction, but I think it's important to clarify what is and is not happening. So with that in mind, if I'm still getting this wrong I hope someone will provide a link which explains the truth

Brian
Welsh Nikonian

  

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elec164 Silver Member Nikonian since 15th Jan 2009Mon 15-Nov-10 05:18 PM
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#27. "RE: There is a lot of garbage on the web."
In response to Reply # 26


US
          

Well Brain, as usual you were able to explain a complex concept in a few concise sentences so that it is more easily understood.

As far as I understand it, you got it spot on!

And as to visionguru’s attributing the phrase ‘diffraction limited’ being created by the author of Cambridgeincolour article, I’m sure they are flattered but I believe they hardly coined the term.

Diffraction limit is a well know phenomenon when designing telescopes. In fact when discussing photographic systems I believe there are at least three main causes of resolution limit. Someone correct me if I am wrong but I believe the proper terms would be film or sensor limited, lens abrasion limited or diffraction limited.

So in that sense a lower pixel density for a given system would show diffraction much later then a higher pixel density for a given format size. Reason being is that a lower density could mean the system is sensor limited in resolvability where as a higher pixel density could be diffraction limited. Of course it also depends on the fine detail available in the scene and the lenses ability to reproduce that scene on the capture medium.

But Brain is correct that this is fretted over entirely too much. A print made from a capture that is sensor limited would look great on its own. That same system when used in which it achieved diffraction limit (by stopping down) during its capture would also produce a print that looked great at normal viewing distance. But put them both side by side under close scrutiny and the print that was sensor limited could very well look better and have a bit more finer detail then the diffraction limited one. But you would never really see it till they were side by side. So that’s why, for a particular format, a higher pixel density can show diffraction that a lower pixel density sensor might not. Trouble is the lower pixel density was not able to record that same fine detail to begin with, so in that sense would hide the affects of diffraction at a particular aperture.

Of course if I got any of that wrong please correct. I don’t pretend to be an expert on this, and studying it is not for the faint of heart for it is quite a complex subject and I hope my rudimentary understanding and explanations don’t muck up the discussion.

Pete

Pete

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visionguru Registered since 03rd Nov 2008Tue 16-Nov-10 07:23 PM
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#28. "RE: There is a lot of garbage on the web."
In response to Reply # 27
Tue 16-Nov-10 07:28 PM by visionguru

Chicago, US
          

Pete: "And as to visionguru’s attributing the phrase ‘diffraction limited’ being created by the author of Cambridgeincolour article, I’m sure they are flattered but I believe they hardly coined the term."
Obviously, "diffraction limit" is not a new word, but the author used it in the wrong and confusing way, his definition is actually different.

Brian: "Well, I'm still with Tom."
I expect Tom agree with me once he gives just a little thought.


Let's consider the following:
On a piece of paper, draw two dots next to each other. You can see 2 dots clearly. Now step back a step, the 2 dots appears closer to each other. Then another step, another step... You will find that the 2 dots quickly merges into one, you won't be able to tell them apart anymore. What does this mean? You've reached your eyes' maximum resolution, you won't be able to tell apart anything finer than those 2 dots at that distance.

This is very similar to a camera. Due to diffraction, if two dots are close enough, they will be indistinguishable on the sensor plane. This limit is imposed upon by the optical system. I probably would define this limit as the minimal angular distance of the two dots with reference to the optical center. This limit has NOTHING to do with the sensor, be it film, or ccd, or cmos, or whatever. When diffraction limit is reached, you cannot tell two dots apart, you cannot with a 6mp sensor, or 12mp sensor, or a 24mp sensor, DX or FX, .... you just cannot.

So, what's the practical significance of the diffraction limit in the context of digital camera? When the pixel density (resolution) reaches the maximum optical resolution (diffraction limit), it's pointless to increase pixel density because there is no further detail, any finer details have lost due to diffraction.

The author defined a camera "diffraction limited" when the pixel density reaches diffraction limit, giving people the impression that the diffraction limit was reached because of the sensor, actually those two are not related at all. The author just borrowed pixel density as a way to describe the diffraction limit (thinking each pixel as 1 dot). Actually we are only limited by the optics, not pixel density.

Consider the following: Car A has 100hp; Car B has 500hp. The speedlimit is 20mph. Yes, Car B reaches speedlimit faster, is that a bad thing? Was the speed limited by the car? 500hp may not be necessary, but it's not all that harmful. Not a perfect example but quite similar to this "diffraction limited" hoopla.

Cheers.





  

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briantilley Moderator Deep knowledge of bodies and lens; high level photography skills Nikonian since 26th Jan 2003Tue 16-Nov-10 10:17 PM
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#29. "RE: There is a lot of garbage on the web."
In response to Reply # 28


Paignton, GB
          

Is this article wrong as well? How about this one...?

I have no connection with either website, they simply came up in a Google search. Maybe I'm not looking in the right places, but I can find no apparently reliable websites saying that pixel size has no impact on when lens diffraction effects become visible

Brian
Welsh Nikonian

  

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visionguru Registered since 03rd Nov 2008Wed 17-Nov-10 12:38 AM
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#30. "RE: There is a lot of garbage on the web."
In response to Reply # 29
Wed 17-Nov-10 12:38 AM by visionguru

Chicago, US
          

>Is
>this
>article> wrong as well? How about
>
this one...?

At a glance, both articles are sound.


>I have no connection with either website, they simply came up
>in a Google search. Maybe I'm not looking in the right
>places, but I can find no apparently reliable websites saying
>that pixel size has no impact on when lens diffraction effects
>become visible

When diffraction becomes an issue at really small aperture, we will notice artifacts, blurred details, regardless of which sensor is used. The image projected onto the sensor is blurred, whatever we do about sensor (big pixel or small pixel), the lost details cannot be recovered because it's not there.

We all have a feeling that when the same picture viewed at 50%, 25%, the picture appears sharper than 100%, and clearner (in terms of noise). This effect was due to physical scale shrinkage, we lost a lot of details, but the edges become shorter, thus appears sharper. This effect is totally indenpendent to motion blur, or out of focus blur, or diffraction blur.

  

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TomCurious Registered since 03rd Jan 2007Wed 17-Nov-10 03:19 AM
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#31. "RE: There is a lot of garbage on the web."
In response to Reply # 28


Bay Area, US
          


>So, what's the practical significance of the diffraction limit
>in the context of digital camera? When the pixel density
>(resolution) reaches the maximum optical resolution
>(diffraction limit), it's pointless to increase pixel density
>because there is no further detail, any finer details have
>lost due to diffraction.
>

Exactly right. This limit depends on the aperture, right? With a larger aperture, you would reach that point of "maximum optical resolution (diffraction limit)", as you well describe it, at a higher pixel density. Which is all we are saying. Higher pixel density == diffraction limit kicks in at a larger aperture.


>The author defined a camera "diffraction limited"
>when the pixel density reaches diffraction limit, giving
>people the impression that the diffraction limit was reached
>because of the sensor, actually those two are not related at
>all.

Yes they are related, see above. Of course diffraction occurs in the lens aperture even without a camera attached. But the term "diffraction limit" is meaningless then. It becomes meaning only if you put some kind of sensor behind the lens and measure what it projects.

You might look at the problem as "aperture of f/5.6 results in diffraction limit reached at 16 MP for a DX sensor" (as an example). Most photographers will look at it the other way around as "with a 16MP DX sensor, the diffraction limit is reached at f/5.6". Both statements say the same thing. Neither side is cause or effect - without having both a lens/aperture and a sensor in place, there is no such thing as diffraction limit.

Tom
Bay Area Nikonian


http://www.tkphoto.me/

  

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visionguru Registered since 03rd Nov 2008Thu 18-Nov-10 09:52 PM
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#32. "RE: There is a lot of garbage on the web."
In response to Reply # 31
Thu 18-Nov-10 10:34 PM by visionguru

Chicago, US
          

Let's consider an 1-dimentional signal system, a voice recorder: a microphone turns voice into electrical signal then records to a tape.

The voice recorder will have a bandwidth limit for many reasons (a simplest one is limited power), there will be a cut off frequency. Any frequency components high than the cut off frequency are lost and will not reach the tape.

The recording media (tape) has a cut off frequency too. Regardless the type of voice recorder, anything higher than the cut off frequency cannot be recorded.

If we gradually improve the resolution of the tape (higher cut off frequency), when the cut off frequency of the tape equals that of the recorder, it's meaningless to improve the tape further because no higher frequency can pass the recorder anyway.

Camera is exactly the same, just in a 2-dimensional form.
Think the closeness of two "dots" as spatial frequency. diffraction limit is exactly a cut off frequency of the optical system: something like when 2 "dots" are closer than xxxxx angular distance wrt the optical center, they will not be distinguishable at the sensor plane.

In the often referenced article, pixel density was actually used to implicitly specify spatial frequency, it's actually a quantity determined by the optical system only, there is no inherent relationship between the two.

When a scene contains mostly low frequency features, the visual effect of the diffraction limit won't be as obvious as a scene with lots of high frequency features. That explains why some people use f/22 without noticing ill effects. The effect of diffraction limit is rather content dependent rather than pixel density dependent. I think the cause of confusion is exactly the mixing up of cause and effect. The use of "diffraction limited" adds more to it, giving an impression that pixel density has anything to do with a purely optical effect.


This was taken by a compact camera (Canon G11), at f/4.5, we can already see the diffraction effect: the fine feathers cannot be distinguished anymore. There are some artifacts showing:


Larger scale features (low spatial frequency) are actually ok. The content of the scene is more directly related to the effect, not the pixel density.

  

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TomCurious Registered since 03rd Jan 2007Thu 18-Nov-10 10:46 PM
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#33. "RE: There is a lot of garbage on the web."
In response to Reply # 32


Bay Area, US
          

So you really think that in this image we could see the effects of diffraction if it were a 1MP camera?

Tom
Bay Area Nikonian


http://www.tkphoto.me/

  

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visionguru Registered since 03rd Nov 2008Fri 19-Nov-10 01:52 AM
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#34. "RE: There is a lot of garbage on the web."
In response to Reply # 33
Fri 19-Nov-10 01:57 AM by visionguru

Chicago, US
          

>So you really think that in this image we could see the
>effects of diffraction if it were a 1MP camera?

No, we can't see it from about 2.5mp (50% resize) for this duck picture.

But the point spread function is spatially unlimited:
http://images.cambridgeincolour.com/tutorials/airydisk-3D.png
(photo credit: cambridgeincolour.com)

It's possible that under certain feature arrangements, there could be interesting patterns in the convolution result, visible even in very low pixel density. Unfortunately, the last time I touched an optics book was decades ago, showing you a proof is beyond my capabilities at the moment.

  

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TomCurious Registered since 03rd Jan 2007Fri 19-Nov-10 07:06 PM
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#41. "RE: There is a lot of garbage on the web."
In response to Reply # 34


Bay Area, US
          

>>So you really think that in this image we could see the
>>effects of diffraction if it were a 1MP camera?
>
>No, we can't see it from about 2.5mp (50% resize) for this
>duck picture.
>


Good, so we're on the same page: The same diffraction that is visible with high pixel density may not be visible with low pixel density. It looks like common sense to me, I can't believe we are discussing this for so long.

Tom
Bay Area Nikonian


http://www.tkphoto.me/

  

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elec164 Silver Member Nikonian since 15th Jan 2009Fri 19-Nov-10 02:55 AM
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#35. "RE: There is a lot of garbage on the web."
In response to Reply # 32
Fri 19-Nov-10 03:01 AM by elec164

US
          

>Let's consider an 1-dimentional signal system, a voice
>recorder: a microphone turns voice into electrical signal then
>records to a tape.
>
I know you provided your tape example to refute what others and myself are saying, but when I read it, it seems to really bolster our argument not refute it.

I think where your argument is stuck is in that the cameras are capturing the same amount of detail. Diffraction starts when light passes through the aperture even when the lens is wide open. When that becomes noticeable is dependent on pixel size.

I found this when trying to research this more. Forgive them for being Canon shooters , but I believe Mr. Brownings discussion and provided examples my put this to rest.

http://photography-on-the.net/forum/showthread.php?t=747761&highlight=7d+diffraction

Pete

Pete

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visionguru Registered since 03rd Nov 2008Fri 19-Nov-10 04:02 PM
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#36. "RE: There is a lot of garbage on the web."
In response to Reply # 35
Fri 19-Nov-10 04:12 PM by visionguru

Chicago, US
          

>I know you provided your tape example to refute what others
>and myself are saying, but when I read it, it seems to really
>bolster our argument not refute it.
>
Well, my intention was only to convince the OP that high pixel density of D7000 is by no means negative, it's has nothing to do with diffraction.

>I think where your argument is stuck is in that the cameras
>are capturing the same amount of detail. Diffraction starts
>when light passes through the aperture even when the lens is
>wide open. When that becomes noticeable is dependent on pixel
>size.
>
I'll borrow a few extreme examples.

Take a picture at total darkness, do you expect to see diffraction effect?

Take a picture of total black sky with 1 distant star (infinitely small), we will get a picture of the "airy disk":
http://images.cambridgeincolour.com/tutorials/airydisk-rings.jpg
(photo credit: cambridgeincolour.com)
Yes, theoretically, we will get a whole image like this instead of just 1 dot.

The content is directly related to the diffraction effect. The scene with many fine details will show diffraction effect at larger aperture than scene with simple details.

Yes, at lower resolution, you will see less effect of diffraction (blurs, artifacts, ... and details too), but it doesn't mean they are inherently related.

How do you think about the following?

(1) Dynamic range: The lower the dynamic range, the less detail we can see, thus less diffraction effect. Ok, we'll come up with a "diffraction limited" dynamic range.

(2) Eyesight: The worse a person's eyesight, the less likely he'll see diffraction effect. Ok, we'll come up with a "diffraction limited" eyesight.

(3) Handshake: The shakier the photographer, the blurrier the image, the less likely he'll notice diffraction effect. Ok, we'll come up with a "diffraction limited" steadiness.

.....
These are probably true, but they are not inherently related to diffraction effect, just like pixel density.

Now we already have "more pixel is bad", what's next? "too much dynamic range", "your hands should be shakier", "you eyesight is too good", "you should crank up the ISO to 2000000000000".

>I found this when trying to research this more. Forgive them
>for being Canon shooters , but I believe Mr. Brownings
>discussion and provided examples my put this to rest.
>
>http://photography-on-the.net/forum/showthread.php?t=747761&highlight=7d+diffraction
>
Actually, there is not much contradition with what I've been saying, except he is trying to distinguish diffraction limited and diffraction cut off frequency, which are just definitions. They are just a "certain" frequency. The whole thing is a basic concept in signal processing, poeple just like to complicate things unnecessarily.

  

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elec164 Silver Member Nikonian since 15th Jan 2009Fri 19-Nov-10 05:55 PM
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#38. "RE: There is a lot of garbage on the web."
In response to Reply # 36


US
          

>Now we already have “more pixel is bad”

No-one is saying here that more pixels are bad. In fact if you read Mr. Brownings discussion you will note he states that “smaller pixels always provide the same or higher resolution”.

I don’t pretend to be an authority on the subject and will defer to someone with more knowledge and facts. And to that end I highly respect Dr. Clark’s opinion on this. My description of him would be to say he is definitely one of the sharper tools in the shed (far sharper then I am for sure). After all, the guy seems to do this stuff for a living, so I assume he might know something about this and be a reliable credible source on this topic.

The link Brian provided earlier in a post to his site did not work for me. But here is another link that has a chart that provides the diffraction size for a given f-stop.

http://www.clarkvision.com/articles/scandetail/index.html#diffraction


So one walks away with the understanding that diffraction is a property of light passing though an aperture. If the pixel size is larger than the diffraction spot by a little or a lot it cannot capture it. If the pixel size is smaller than the diffraction spot it can then be imaged. And a slight amount of diffraction can be corrected with Adaptive Richardson-Lucy Deconvolution algorithm. So in that sense having smaller pixels will always be better and no worse than a larger one

Sorry Brian, I will let this drop. As the popular news channel saying goes “we report, you decide, fair and balanced”

Pete

Pete

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briantilley Moderator Deep knowledge of bodies and lens; high level photography skills Nikonian since 26th Jan 2003Fri 19-Nov-10 04:15 PM
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#37. "RE: There is a lot of garbage on the web."
In response to Reply # 35


Paignton, GB
          

>...but I believe Mr. Brownings discussion and provided
>examples may put this to rest.

Yes, let's hope so

Brian
Welsh Nikonian

  

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Len Shepherd Gold Member Nikonian since 09th Mar 2003Fri 19-Nov-10 06:50 PM
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#40. "RE: There is a lot of garbage on the web."
In response to Reply # 31


Yorkshire, GB
          

> When the pixel density (resolution) reaches the maximum optical resolution (diffraction limit), it's pointless to increase pixel
>density because there is no further detail, any finer details
>have lost due to diffraction.
This is part ignoring basic physics - part in that sensor resolution in isolation (or film resolution in isolation) NEVER contributes 100% to file resolution.
On a lens that peaks at f8-11 because file resolution is roughly made up of 50% lens resolution and 50% sensor resolution f2.8 and f22 rarely deliver less than 85% of f8-11 detail.
So - if this nonsenses about pixel size affecting diffraction was true it would also affect wider aperture resolution

Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.

Len Shepherd

  

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TomCurious Registered since 03rd Jan 2007Fri 19-Nov-10 07:45 PM
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#42. "RE: There is a lot of garbage on the web."
In response to Reply # 40
Fri 19-Nov-10 08:27 PM by TomCurious

Bay Area, US
          

>So - if this nonsenses about pixel size affecting diffraction
>was true it would also affect wider aperture resolution
>

This post of yours here is actually the first one about pixel density affecting diffraction. This is nonsense. Neither "affects" the other. They both jointly affect the image, just like oven temperature and cooking time affect the pizza. If you don't care about the pizza, then temperature and time have nothing to do with each other. If you don't care about the image, then diffraction and pixel density will have nothing to do with each other, either.

Tom
Bay Area Nikonian


http://www.tkphoto.me/

  

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dankeny Gold Member Nikonian since 29th May 2006Sat 13-Nov-10 04:46 AM
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#21. "RE: D7000 & Diffraction"
In response to Reply # 0


Roland, US
          

Just stop reading and shoot. The 7k is too cool to miss. If you listen to all the web experts you will worry, not shoot. If you can SEE the problem in your images, then worry. I have never see diffraction in any of my images. I shoot at f22. I guess I'm just not good enough for it to become evident. Problem solved.

David

  

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NikonHank Silver Member Nikonian since 14th Jan 2009Sat 13-Nov-10 02:25 PM
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#22. "RE: D7000 & Diffraction"
In response to Reply # 21


Howell, US
          

Hi David:

Actually what you say is the bottom line. Enjoy the camera, shoot and if not happy with the result, work on technique, composition, etc.

It's easy to get caught up in a camera's specs and technology, lenses, and the laws of physics. However, the point of it all is to produce pictures that are pleasing to the eye and interesting. As a novice, it's not going to be the camera, lenses or diffraction that limits me from taking great pictures.

Have a good day,

Hank

Visit my Nikonians gallery.

  

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visionguru Registered since 03rd Nov 2008Sat 13-Nov-10 03:12 PM
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#23. "RE: D7000 & Diffraction"
In response to Reply # 0


Chicago, US
          

I would just ignore this "diffraction limited" thing, which is a misleading term created by the often quoted article:
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

In trying to associate inherent optical resolution limit with digital camera sensor pixel size, the author shows that he doesn't have thorough understanding of the topic. The diffraction limit is relevent to the maximum spatial frequency that can pass the optical system, has nothing to do with the sampling frequency of the sensor.


In real life, the spatial frequency in a scene is limited, and our eyes (2 perfect cameras, btw) also have limited resolution, so you can safely use very small aperture without noticeing degradation in image quality.

  

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Gamecocks Silver Member Nikonian since 22nd Jul 2010Fri 19-Nov-10 11:34 PM
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#43. "RE: D7000 & Diffraction"
In response to Reply # 23


Joanna, US
          

Simple solution - go back to the Kodak insta-matic and not worry about all the technical stuff. If it works, it works; if not, try something else until you are satisfied. Good luck with whatever happens.

Nobody should seek his own good, but the good of others. <><

  

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