After playing with D7000 for a few weeks, I found that D7000 needs faster shutter speed to counter hand shakes comparing with D300 or D5000.

The old rule of thumb is: Shutter speed = 1/focal length.

Some say for DX camera it's modified as: Shutter speed = 1/ (F.L. * 1.5) This is actually taking into account sensor pixel density, not much to do with DX or FX. If we take a picture at the same focal lengh with a D3X (24MP) and a D300(12MP), the D300 picture is roughly the crop of D3X picture, the rule for the shutter speed should be the same. Therefore, it's about pixel density, not format.

In the same spirit, the increase pixel density of D7000 will have effect on this rule of thumb. The line magnification of D7000 vs D300 is about 115%. If you need shutter speed 1/(F.L. * 1.5)on a D300, you will need 1/(F.L. * 1.75) on a D7000.

On D7000,
at 50mm, you'll probably need 1/85"
at 70mm, you'll probably need 1/125"

I guess this maybe the very reason behind some "not sharp" complaints out there about D7000.

Well, this is far from anything scientific, just that as the pixel density increases, the rule of thumb might need to be revised too.

What do you think?

Jay
- Chicago Nikonian

>Well, this is far from anything scientific, just that as the
>pixel density increases, the rule of thumb might need to be
>revised too.
>
>What do you think?

I agree. And it's a point well taken.

Posted on this about a month ago, saying the same thing, but with far less mathematical support.

Keep in mind though that the increased pixel density makes camera shake markedly noticeable at 100% magnification, or in really large prints.

Apart from that, the technique used with a D300 or D40, all other things being equal, might look just as fine in a 12x18 print with a D7000.

The more dense sensor simply reveals more of what was there all along.

www.billkeane.zenfolio.com

>Some say for DX camera it's modified as: Shutter speed = 1/
>(F.L. * 1.5) This is actually taking into account sensor
>pixel density, not much to do with DX or FX.

Actually, it is to do with the camera format (DX or FX). Here's why...

The traditional "1/FL" rule of thumb was formulated specifically for 135-format film (the same frame size as FX). It is based on the reproduction ratio (magnification), which at a given subject distance is proportional to the angle of view that a given focal length provides on that format. The greater the magnification, the narrower the angle of view and the faster the shutter speed needs to be to avoid camera shake blur.

On DX, a given focal length lens has an angle of view 33% narrower, so to maintain the status quo you need a shutter speed 1.5x faster.

>Well, this is far from anything scientific, just that as the
>pixel density increases, the rule of thumb might need to be
>revised too.
>
>What do you think?

Increasing pixel density within the same format does make a difference to the required shutter speed, if you view the images at the same magnification - say 50% or 100%. If you're making a print of the same physical dimensions, the rule of thumb doesn't change.

Brian
Welsh Nikonian
Check out the Nikonians Team pages

The required shutter speed also requires good hand holding technique. But some have found the they may need to bump up the speed because of personal issues. But it is a start to finding the value that works best for you.

You may also need to adjust the shutter speed if your a panning.

George
My Nikonian Galleries

Precisely!

The rule of thumb has only ever been a starting point, and each individual photographer needs to work out their own "safe" speed for each type of situation.

Brian
Welsh Nikonian
Check out the Nikonians Team pages

Brian,
With digital cameras, we examine at 100% pixel leve to determine "sharp" or not.

D300 (12mp) image is almost exactly the center crop of D3X (24mp). With everything being the same (including lens, shutter, camera poistion.....) both will be affected by the handshake the same way. So, it doesn't directly related to DX or FX, it has everything to do with sensor's pixel density. Yes, DX often has higher pixel density, but not D3X, which is similar to D300 in this regard.

Jay
- Chicago Nikonian

>With digital cameras, we examine at 100% pixel leve to
>determine "sharp" or not.

Viewing at 100% is of no benefit to judging sharpness, and may even be detrimental. Using 50% view or less is a better option.

Either way, unless we have a REALLY large monitor. we don't view a whole-frame image at 100%, and it's actual viewing - of the whole image at a typical print size - that the hand-holding rule of thumb is based on.

>D300 (12mp) image is almost exactly the center crop of D3X (24mp).

To be pedantic, the D3X's DX Crop Mode is about 10.5 MP, which is closer to the D200 than the D300. An FX frame has about 2.3 times the area of a DX frame.

>With everything being the same (including lens, shutter, camera
>position.....) both will be affected by the handshake the same way.

Only if you magnify the image the same amount for viewing / printing. If you print the DX frame at 12x8 and the FX frame at 12x8, the DX image will have been magnified more, and will need a higher shutter speed to maintain the same apparent steadiness.

Trying to keep pixel count out of it, the same was always true with film. A 35mm camera required a faster "safe" shutter speed than an APS camera, when the focal length, subject and distance were the same. A medium-format camera needed a faster one again.

To repeat - the rule of thumb is about angle of view and magnification, not about format - if you are comparing the same physical size print. Like I said, the pixel density only makes a difference if you are viewing everything at 100% (or at 50%).

Brian
Welsh Nikonian
Check out the Nikonians Team pages

As Brian said, it's really a function of magnification. Comparing cameras with different pixel densities, if the magnification used is the same, and below the resolution of the camera with the lower pixel density, the needed shutter speed is the same.

Remember, however, the 1/FL rule came from film days when the largest print was usually 11x14 or less. That's equivalent to ~ 25% pixels for a DX camera of 12-16MP, and isn't enough (at least for me) to provide maximum sharpness at 100% pixels without VR. Try an experiment shooting the same image at higher and higher shutter speeds (again VR off), and see what's needed for maximum sharpness. With my shaky hands it's about 1/3-4FL. Good reason for VR or a tripod if maximum sharpness is the goal.

Marty

Visit my Nikonians gallery.

>With digital cameras, we examine at 100% pixel leve to
>determine "sharp" or not.

Hi Jay,

I know this comment was directed at Brian but I do want to make a point. 100% viewing for assessing sharpness or not is not a good rule of thumb. That's because sensor size (in pixels) varies. That means a 100% view varies too as to what you are looking at. What's important is what is sharp at the final intended viewing size and viewing distance, be it print or monitor. These latter two variables define what's called the circle of confusion, the maximum acceptable degree of unsharpness for the application in mind.

Peter

Hi Peter,
Within the context, "sharpness" probably is better described as "motion blur effect caused by hand shake on sharpness". When such effect is suspected, many will view at 100% to examine.

Imagine a simplified 1-dimentional camera with only 2 pixels next to each other: A & B. If from start to the end of the exposure, pixel A shifted to the position of B, there will be obvious blur at pixel level.

Now if we increase pixel density, say 4 pixels within the same sensor, it's easy to see that we need twice the shutter speed to counter the same hand shake. This has nothing to do with being DX or FX, just pixel density.

Yes, different people have different standards about sharpness, blur, preferred viewing size, and preferred print size, but for the same individule, his standards are likely quite consistant, it's HIS rule of thumb.

I can shoot D300 (focal length 70mm)confidently at 1/60", but with D7000 I need 1/100" to get decent percentage of keepers. With the increased pixel density of D7000, people may need to adjust their rule of thumbs, that was my point.

Jay
- Chicago Nikonian

This is a complex issue with both sides having a bit of credence in my opinion.

Determining the actual resolution of the sensor is complex for several reasons. The fact that it is a Bayer filter sensor using an AA filter and that the sensels are not square are some of the reasons behind the complexity.

But if we for the sake of simplicity ignore those complexities and just consider pixel pitch we can see that a greater pixel pitch would be more sensitive to camera movement. This example is just a hypothetical exercise. For instance let’s assume a pixel pitch of 4.6 microns for the D7000 and 5.5 for the D300s/D90. Now take a target in which a black line was the same size of the D7000 sensel of 4.6 microns with white on either side of it. If we mount the camera rock steady so that the line on the target completely covered the sensel, we would get a solid black line on the image. Now if we did the same for the D300s/D90 the line on the target would only fill part of the sensel with some white also being covered making the data collected less black or off-black.

Now introduce a 1 micron camera movement centered on the sensel meaning a half micron movement left to right. Now the D7000 sensel that originally was solid black has some white areas part of the time, as well as the white areas having some black. So now the line in the image is less black, and the white areas on either side are less white making the contrast barrier lower and the image appear less sharp. But the same movement on the D300s/D90 still would fall upon the same sensel therefore providing the same signal. It’s just that the white area shifted back and forth from being half and half to one side or the other. But the image will still show the line as the same off-black, so in essences was not able to detect the movement.

Now make an 8x10 print and view it at the same viewing distance and they probably would appear equally as sharp being that the more black line surrounded by the off white of the D7000 would appear the same as the slightly off-black of the D300s/D90 capture because of the limited acuity of human vision.


As to PP, well for those saying they used the same settings for the D???? and the D7000, and the D7000 prints look softer are not taking the pixel density into account. Being the smallest sensel sized camera produced by Nikon means that you need to alter your settings for sharpening to exact a similar appearance. For instance Fraser and Schewe in their Real World Sharpening Book state “a rule of thumb that served Bruce well is to keep the sharpening haloes no smaller than 1/100th of an inch and no larger than 1/50th of an inch, with the smaller number being preferred for small(up to 11x14)prints”. Well a 1/100th or 1/50th of an inch for a given enlargement size means that there are more pixels that need to be affected in the D7000 file then the D300s/D90 file. So you need to bump up the settings for the D7000 to achieve a similar appearance.

It truly is a complex issue and I can see a lot of merit in all the opinions expressed by everyone here so far. A very informative thread.

Just my thoughts on this.

Visit my Nikonians gallery.

>Imagine a simplified 1-dimentional camera with only 2 pixels
>next to each other: A & B. If from start to the end of the
>exposure, pixel A shifted to the position of B, there will be
>obvious blur at pixel level.
>
>Now if we increase pixel density, say 4 pixels within the same
>sensor, it's easy to see that we need twice the shutter speed
>to counter the same hand shake. This has nothing to do with
>being DX or FX, just pixel density.

You're still ignoring the size (or magnification) at which the resulting image is viewed. But maybe I haven't explained this well enough so far, so let's take another example...

Imagine you have two cameras with sensors of the same physical dimensions - FX - but one with 360x240 pixels (camera A) and one with 240x160 pixels (camera B). If you view images from A and B at 100% on a monitor, then the 360x240 image will look larger and will, as we have both been saying (and assuming all other factors are equal), require a higher shutter speed to avoid camera shake blur.

Now add a third camera (camera C), with a sensor of smaller physical dimensions - DX - but also with 240x160 pixels. Fit camera C with a 200mm lens and camera B with a 300mm lens so that they have the same angle of view. Now view images from cameras B and C at 100%. They will look just the same (apart from DoF issues), so logically camera B and camera C will need the same shutter speed to avoid camera shake blur.

By extrapolation, a DX camera with a 200mm lens needs the same "safe" shutter speed as an FX camera with a 300mm lens. Which was the original question

Brian
Welsh Nikonian
Check out the Nikonians Team pages

>By extrapolation, a DX camera with a 200mm lens needs the same
>"safe" shutter speed as an FX camera with a 300mm
>lens. Which was the original question


Yes, and the ONLY reason it seems not to be the case is simply because 100% magnification (via one-click in most browsers) of a more densely pixeled sensor is simply showing more minutely what a less densely pixeled sensor couldn't resolve.

At the other extreme, a 100mp sensor captured image, viewed at 100%, on a standard size monitor might resolve all sorts of "shake" that couldn't possibly be visible, even on a large, 20x30 print.

The very best technique, on the very same image, captured at 6mp, and also at 100mp, viewed at 100%, would look markedly different from one sensor to the other.

www.billkeane.zenfolio.com

"You're still ignoring the size (or magnification) at which the resulting image is viewed. But maybe I haven't explained this well enough so far, "
Brian, What you explained are correct, just not the essential causes.

Technically, handshake caused blur can be modeled without looking at the picture at all. If during the exposure, due to handshake, one pixel crosses other pixels position, the picture is blurred, even if it's noticeable for one person, while not noticeable for another, it doesn't matter, it's a fact.

Given the same handshake speed and same focal length, twice the pixel density needs twice the shutter speed to avoid one pixel crossing to other pixels's positions. The difference maker is pixel density. DX or FX or medium is not relevant even if one format often has higher pixel density.


Jay
- Chicago Nikonian

>Technically, handshake caused blur can be modeled without
>looking at the picture at all.

BUT - we are (or were, at least) talking about the traditional Rule of Thumb. This was/is based on viewing the whole image at a standard size, as a practical guide to hand-holding, and is what you persistently ignore in your "theoretical" argument.

>Given the same handshake speed and same focal length, twice the
>pixel density needs twice the shutter speed to avoid one pixel
>crossing to other pixels's positions.

Yes, IF you are viewing the images at the same magnification, but NOT if you are viewing the whole image at given physical dimensions (which is what the Rule of Thumb specifies).

>DX or FX or medium is not relevant...

I'm sorry, but it really is relevant to the Rule of Thumb, as already explained.

I think we have debated this for long enough...

Brian
Welsh Nikonian
Check out the Nikonians Team pages

"Yes, IF you are viewing the images at the same magnification, but NOT if you are viewing the whole image at given physical dimensions (which is what the Rule of Thumb specifies)."

Somehow, the differences in this debate seem rather pholosophical than technical. An important rule of thumb in science and technology is occam's razor. Including viewing size etc. subjective components can complicate the issue unnecessarily.

If we have to include viewing size (or print size, viewing distance, viewer's vision, viewing lighting condition, etc...),

(1) What if I don't know the viewing/printing size? In that case, I would require my pictures to retain as much information as possible, all the way down to pixel level.

(2) If I know the viewing/printing size, I would shoot to the size.
D7000 can shoot "M" = 9MP, "S" = 4MP. Shooting at 16MP knowing that a smaller size is sufficient seems wasteful at least.

I believe you are missing the point. An 8x12 print from a D90 and a D7000 with the same amount of camera shake will look the same to the viewer no matter what the viewing distance. The fact that the blur is spread over more pixels in the D7000 is irrelevant in that when printed, the measured blur on the print is the same size as the D90. Reason being is that when printing at 8x12 the D90 will print at about 357 PPI and the D7000 will be 410 PPI.

The complaints seem to mainly stem from people viewing the images on screen at 100% and not examining equivalent print sizes. At 100% view the blur will appear larger and more apparent because of the higher pixel count. That’s because monitors can only display actual pixels and will display both at the monitor’s resolution of about 100 PPI. If you were lucky enough to have a duplicate image taken of camera shake blur from a D90 and D7000 and wanted to compare the results on screen at 100%, you would view the D90 image at your normal seated position. But when switching to the D7000 image you would need to slide your chair back about a foot to compensate for the greater enlargement (about 43 inch for the D90 long side and 50 inch for the D7000). At that point the images should appear the same.

At least I believe that is the way it should work.

Pete

Visit my Nikonians gallery.

>I believe you are missing the point. An 8x12 print from a D90
>and a D7000 with the same amount of camera shake will look the
>same to the viewer no matter what the viewing distance.

My question is: What's the point of shooting at 16MP? knowing that many of the pixels are junk? Why not just shoot 9MP or 4MP instead?

To me, if I shoot at 16MP, I want every pixel counts, same as with 9MP or 4MP. Some people may want to do cropping, pixel level performance cannot be discounted.

IMO, stressing print size or view size is not a valid argument here.


Jay
- Chicago Nikonian

>My question is: What's the point of shooting at 16MP? knowing
>that many of the pixels are junk? Why not just shoot 9MP or
>4MP instead?
>

The pixels aren’t junk and do matter. If you are using the D7000 over the D90 in an attempt at gaining greater reach, then yes you will need to refine your technique and possibly need to shoot at a higher shutter speed to reduce effects of camera shake. On the other hand, if you stayed with the D90 and just got a longer focal length lens, you would still need to make the same adjustments and improvements as you did with the D7000 using the shorter focal length and cropping. In that respect there is no free lunch.

But if using the whole capture or similar amounts of cropping, then a print made from either camera will look the similar(same).

Pete

Edited to add:
I originally had said the same, but it should be similar in that while the motion blur would be identical, the D7000 has the ability of capturing slightly more detail then the D90. Personally if I had a D90, I might pass on moving up unless the more pro feature set was desirable. Image quality wise I don’t believe there is a significant reason to upgrade, but thats just me.

Visit my Nikonians gallery.

There is a lot to talk about.
I have recently checked out top grade £2000 monitors - and reached the conclusion I expected to reach - the best monitors are not particularly sharp
The reason top monitors are not particularly sharp is straightforward - they do not have top resolution
I can print out a 27 inch diagonal print from 12 MP with interpolation from 12 MP at 300 dpi, at 600 dpi with interpolation from a loaned D3x, or at 600 dpi without interpolation from 30 MP medium format.
Although the best monitors are extremely good they rarely achieve 100 dpi - which would usually be a poor standard for print making viewed at full screen equivalent size.
Whilst viewing at 100% has it's uses - you still do not get very high resolution compared to printing in the range of 200-600 dpi.
100% viewing is best reserved for it's intended purposes - which are mainly for checking for edge halos when sharpening, or for pixel by pixel retouching.
Back to basics - the standard for depth of field seems to be based on a 10x8 inch print viewed at 12-15 inches using a standard lens for the format for a 12 foot wide subject - and being prepared to accept an edge blur of 1/100th of an inch as OK - as the eyes resolving power cannot detect differences this small.
This remains a good starting point because the eye can see the corners of a 10x8 inch print at 12-15 without being swiveled.
It follows a 20 inch wide print looks sharp viewed at 24-30 inches- and so on.
Modern equipment can often achieve better - but you may have to crop the image or view through a magnifying glass to see the differences.
If the technique used is just good enough for 1/100 edge blur and no better a significant crop can increase the edge blur to a not sharp looking 1/50th of an inch.
Digressing the closer you focus the greater the magnification, and the greater the magnification the greater the chance of unsharp edge blur. The suggestion I mentioned above of a 12 foot wide subject for dof calculations goes back at least 50 years. Interesting Nikon imply an 8 foot wide subject for the 1x focal length guide for sharp images in the 105 VR notes. The difference between 8 and 12 feet wide is not particularly important in an era of cameras with vibration damping, or different people having different hand holding ability.
What is important is focusing for a 4-6 feet wide subject generally requires 1 shutter speed faster than for 10 feet-infinity to compensate for the extra magnification shooting closer. Similarly 3-6 feet wide subjects usually require 2 shutter speeds faster, and so on.
Summing up higher MP does not in itself require faster shutter speeds to achieve the resolving limit of the human eye.
The concept to grasp is when going in "closer" than normal eyesight limits camera shake is magnified. A faster shutter speed will often then be needed to get a sharp image after significant cropping.
For a 10x8 inch print a normal shutter speed remains OK.

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

>Summing up higher MP does not in itself require faster shutter
>speeds to achieve the resolving limit of the human eye.
>The concept to grasp is when going in "closer" than
>normal eyesight limits camera shake is magnified.

Bingo.

www.billkeane.zenfolio.com

>Back to basics - the standard for depth of field seems to be
>based on a 10x8 inch print viewed at 12-15 inches using a
>standard lens for the format for a 12 foot wide subject - and
>being prepared to accept an edge blur of 1/100th of an inch as

This is the second post you’ve mentioned this fact, and the first time (well now the second time ) I have ever seen subject size mentioned when discussing DOF. Could you please point to a reference that discusses this so that I can learn why they mention it?

In my limited understanding, DOF is based solely on the average visual acuity of human vision. The average person viewing a subject at a distance of 12 inches has a visual acuity of about 1/300th (actually it’s more like 1/287th ) of an inch. What that means is if the average person looked at an image of alternating black and white lines that were 1/300th of an inch wide at a distance of 12 inches, they would see a solid gray mass. If the lines where 1/100th of an inch wide then at a 12 inch viewing distance they would no longer blend them together to see gray but would see them as individual lines. But increase the viewing distance of the image with line widths of 1/100th of an inch to 36 inches, and the average person will again see a solid gray mass because the average visual acuity of human vision at 36 inches is about 1/100th of an inch. So when determining DOF you must keep in mind the size print to be made and the distance it will be viewed at. To capture that amount of the CoC that is needed for that specific DOF you need to factor in the size of the capture medium, any amount of cropping you may do, the focus distance and aperture. So when determining the CoC needed for a specific DOF for a given print size of a given capture medium size, the MP count is irrelevant.

As to monitor resolution, Len’s correct that desktop monitors will range from about 85 PPI to 133 PPI. What you are paying for in that more expensive higher end monitor is not more resolution, but a better color gamut. Low end cheaper monitors generally use TN panels which have poorer viewing angles and color fidelity across the screen and generally only achieve sRGB at best. The higher end more expensive monitors employ IPS panels which provide increased viewing angles with better color fidelity across the screen that approaches Adobe RGB with some even exceeding Adobe RGB color space. And I believe the decision by manufactures to hold down the resolution is one of cost and practical application. If you measure the average viewing distance of a monitor on the average desktop you will find the distance to be around two feet. I just measured the one I am working on and the distance is 27 inches. At a 27 inch viewing distance the average person’s visual acuity is going to be around 1/128th of an inch. So the 100 PPI of the monitor is just larger than what the average person can resolve to begin with. So yes they could make the LCD panel with greater resolution, but at the average viewing distance the average person would not be able to see it anyway. If you want to prove this to yourself just open a blank image in PS using a white background, create two black pixels spaced one pixel apart then view them at 100% view with your normal viewing distance. If your acuity is average you will be able to just make out that they are two separate spots. If the screen resolution was higher, you most likely would have seen them as blended together as one.

But having said all that, I don’t believe that was the intent of the original post, nor what is being discussed. The question is will a smaller sensel possible show smaller amounts of motion blur. Well the difference from a 12 MP DX camera and the 16MP DX camera is less than one micron. In general, I would say no it would not. The logic behind the smaller sensel having a greater ability to show motion comes from the fact that digital sensors only sample the real scene. Sometimes the edge of a detail will only fall upon part of a sensel. If that’s the case then a slight amount of movement will be unnoticeable for the edge will just shift within the sensel and not spill over to the next one. But do you really believe you are going to see an actual difference between a 4.6 micron sensel and a 5.3 micron one (difference of 1/24000th of an inch)? I sure don’t. And part of the reason that the detail edge sometimes looks soft (aside from the AA filer) is the fact that sometimes the detail does not cover the whole sensel therefore has a different value then the actual detail does (lower edge contrast which USM helps to counter).

So I believe, as Len and others appear to do, the demon is 100% view and failing to keep in mind what you are looking at. A lens can only truly focus on a single 2 dimensional plane in a 3 dimensional field. So if when using 100% view you can find that point, and if the 12MP camera was focused on the same plane as the 16MP camera, then that point should look equally sharp in both images because in theory the point of focus will be rendered as a point source (in practice aberrations often prevent a detail as being rendered as point source and all points are renderer as blur circles). Trouble is that we usually are only looking at the areas covered by the DOF (a blur circle or better known as the CoC). In that case looking at an area away from the focus plane at 100% view, the 12MP image will look sharper than the 16MP image. Not because motion blur was detected by the 16MP image that was not in the 12MP image, but because the 16MP image at 100% view is a greater enlargement than the 12MP image. And as we know, apparent sharpness is dependent on visual acuity which is dependent on amount of enlargement and viewing distance. If you are looking at the 12MP image at 100% at your normal seated position, then if you want the 16MP image to appear equally as sharp at 100% view, you then need to slide your chair back to increase your viewing distance a few inches. Yes the motion is spread out over more pixels, but I believe the same amount of motion is detected and appearant.

Also I believe part of the problem comes from a lack of understanding of the PP workflow. I have seen many people provide examples of raw conversions where they state that they used the same settings and look how soft the D7000 is compared to the DXX/DXXX 10/12MP image. Well yes, the D7000 having a greater pixel density needs more sharpening applied. Most sharpening techniques actually do not sharpen but increase edge contrast. The effect of edge contrast is dependent on the size of the halo. Because of the greater pixel density, you need to affect more pixels on the D7000 image then you would on say a D90 image. So you need to alter the settings for pixel, radius and amount when processing the D7000 file and most likely use a greater setting then you would for a D90 file. And as to sharpening, I also wonder about the Picture Control settings used in camera and alterable in ViewNX2/CNX2. Does Nikon take the pixel density in account, therefore a setting of 4 on the D7000 is applying more sharpening to the image then say on a D90 (in my opinion it should be)? Or does a setting of 4 in Picture Control apply the same amount of sharpening regardless of the pixel density or camera model? If the latter is the case, then it's understandable to me why the D7000 image would look softer.

I believe it is simple as that, I’m sure other opinions will vary. But this has been a great discussion so far and very informative.

Pete

Visit my Nikonians gallery.

>This is the second post you’ve mentioned this fact, and the first time (well now the second time ) I have ever seen
>subject size mentioned when discussing DOF. Could you please point to a reference that discusses this so that I can learn
>why they mention it?
Once upon a time people knew the web was not always an accurate source of information.
For more complex topics web sites generally avoid more complex technicalities - because most of their core customers are not much interested in technical detail.
Good hard copy sources include the Kodak Professional Guides, Canon's EF Lens Work III, the old Focal Press Encyclopedia of Photography - or the more recent Focal Press Manual of Photography Edition 9 still exist
There is a recent edition 10 with new USA authors - as yet I do not know how good the 10th edition is.
There is (as always) debate in photography. Dof is often based on a COC of about 1/30th of an inch - the limit the eye can determine without going to minimum focus (10-12 inches) and having to swivel the eye to see the picture corners. Nikon works to 1/30.
Others "argue" for /25 based on minimum focus distance. Kodak support 1/25 for forensic work when the finest possible detail is likely to be required - in the long out of print research in the late 1950's that established with importance of the T factor and varying close up apertures with many modern lenses - now often referred to as "focus breathing".
Sorry - I do not know a good reliable web source.

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

>Sorry - I do not know a good reliable web source.
>
>
Thanks for the references Len. Admittedly my first serious study of photography was back in 1971, and garnered information from a fellow serviceman who worked as a photographer for a local paper in Alaska who taught me how to develop B&W film and prints at the service club, as well as Kodak’s ‘Pocket Guide to Photography’. Neither got that technical and both were more practical. I have Hedgecoe’s ‘The New Manual of Photography’, but again he really gives a more practical guide with a bit of technical facts.

And I was not just asking for a web reference, I actually prefer books in hand over reading text on a monitor!!

Also, I never take any one source as authoritative, no matter how well respected. Just look at the nightmare Kodak created when it inadvertently left out the exposure compensation instructions for use of its gray card when they decided the packaging and instructions needed an update back in the 1970’s. The error went unnoticed and was finally discovered, and the instructions were finally added back in somewhere in the 1990’s.

Pete

Visit my Nikonians gallery.

>I never take any one source as authoritative, no matter how well respected.
Any source that suggests 18% is a mid grey or depth of field is 33% in front and 66% behind the point of focus is not authoritative
I usually check out the maths supporting some of the theory before forming a conclusion.
I mentioned the Focal Press Manual of Photography acquired by USA owners and now in 10th edition with a team of new USA authors.
I have not checked out the ability of the new USA authors.
The Kodak Grey card error is one well known mistake - another is the Nikon dof mistake (for over a decade) in the instructions for the 60mm AF-d.

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