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An over fertile imagination perhaps, all about the D400...

nrothschild

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"RE: I really don't see the relevance of this discussion Neil..."

nrothschild Neil is an expert in several areas, including camera support Registered since 25th Jul 2004
Wed 16-May-12 08:43 AM | edited Wed 16-May-12 08:44 AM by nrothschild

I'm going to address my alleged "factual errors" first:

>> 1. According to Cambridge in Colour's calculator, diffraction limits
>> the system somewhere between f/11 and f/16 on a 24 MP 1.5x sensor. Of
>> course, this depends on print sizes and viewing distances. Such a
>> camera would be diffraction limited at f8 given 16" x 24" prints viewed>> from 10" away.

From Cambridge In Color's diffraction part 2 article:

Click on image to view larger version


Sean goes into a long discussion about all the reasons why there is no precise "correct" or "incorrect" focal ratio where diffraction is a concern. He attempts to deal with it in part 2 with a range of possible (and, in my opinion, very reasonable) values.

I actually had an interesting email exchange with him recently about the visual model in his diffraction part 1 article, in the context of perceived sizes of airy disks verses theoretical actual sizes and how he represented that in his model. So I think I have some insight into his thinking.

Although I tried very hard not to suggest some certain precise focal ratio, I did say the following:

"Since I use a TC17 more than you do, this is a particular concern of mine because that TC probably ought to be shot at f/10 to f/11 when the situation allows."color=red>

I think that is 100% consistent with your quoted source, per the above computation on his own model.

Elsewhere recently I suggested diffraction on a 24 mpx sensor will start just narrower than f/5.6 and I think that is also 100% consistent with the above.

You suggest that Sean suggests diffraction starts between f/11 and f/16 but you don't provide an exact context. Since you mention print size, I'll assume you used the calculator in his part 1 article with some unspecified set of parameters.

Any time you use a diffraction calculator in the context of "standard print size" then there is a critical assumption that the image is either un-cropped or cropped only on the long side to conform to the final aspect ratio.

I would suggest that in the case of an un-cropped image we wildlife shooters don't really care about endless searches for more resolution, the same way that 12 mpx is more than enough resolution for most photographic subjects where the image should be well framed and cropped only to final aspect ratio.

Where we need "more" resolution (sensor density) is where we are deeply cropping an image. In that case, the appropriate "standard output size" in a diffraction computation could approach 100% pixels, which is the basis for my illustrated example here suggesting diffraction could start as wide as f/5.9, per Sean's computation.

The "right answer", if there is one, at least partly (and primarily) depends on the depth of the crop and we could go round and round about that forever. But when you start talking about equivalence between, say, 24 mpx DX and 300mm verses something like 500mm and equivalent 12-15mpx DX (such as the D800 provides) then I believe you need to be looking at diffraction more from the context of 100% crops than 8x10 standard output sizes from uncropped images.

I just said "more from" because I am (again) going out of my way not to get nailed down to some specific number that you will then declare as "factually in error" based on the assumptions of your choice. But it is a mathematical fact that the deeper you crop the closer you get to using 100% pixels (per Sean's very conervative numbers above) to accurately model "standard output size".


>> 2. In truth, both the MFD and magnification for the 500 f4 AF-S and>> AF-S II are identical; the maginification is 1:8.2 (autofocus). Nik>> on simply corrected the spec when they introduced the AF-S II. You >> can verify this yourself.

I would not know where to find Nikon's "official and final" specs on either out of production AF-S model. My lens came without the standard lens manual, which might list that spec but in any case I have no access to AFSII docs. That is why I used Roland's numbers, with a caveat at the end, and mentioning that I did not believe his number to be correct, simply based on images I've shot at or very near MFD, per the exif focus distance. But it is irrelevant to the discussion since you later better defined the nature of your concerns there (which was not clear at first mention).


Attachment#1 (jpg file)

_________________________________
Neil


my Nikonians gallery.

This is a hot, active topic! An over fertile imagination perhaps, all about the D400... [View all] , richardd300 Silver Member , Thu 26-Apr-12 07:41 PM
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                                             Reply message We've seen (and heard) this before Neil...
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Reply message There are two types of too close Neil.
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               Reply message RE: There are two types of too close Neil.
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                    Reply message I really don't see the relevance of this discussion Nei...
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                         Reply message Okay Neil, let's look at the pixel level...
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                              Reply message RE: Okay Neil, let's look at the pixel level...
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                                   Reply message I'm not sure where you're headed with this Neil...
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                                        Reply message RE: I'm not sure where you're headed with this Neil...
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                              Reply message I was too polite to comment there Richard...
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                              Reply message I'm all ears and eyes Neil...
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          Reply message That is just plain misleading Neil...
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               Reply message No Jim, I was NOT misleading...
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                    Reply message I'm not speaking for Jim or Jay...
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                    Reply message RE: No Jim, I was NOT misleading...
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