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

nrothschild

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"RE: An over fertile imagination perhaps, all about the D400?"

nrothschild Neil is an expert in several areas, including camera support Registered since 25th Jul 2004
Wed 09-May-12 11:15 PM | edited Wed 09-May-12 11:37 PM by nrothschild

Edit: this reply was edited to correct an egregious error I made in computing the effective resolution of Perrone's image so you may need to re-read it.

Just to put some numbers behind Perrone's example...

Perrone downsized the image to 1600x1068, which is about a 5:1 downsizing. At this image size the effective resolution is 1600/2/36=22 line pairs per millimeter (LPPM).

The image was shot at f/11 which is well past the theoretical diffraction limit of around f/7.2 so the image was "impaired by diffraction". At f/11 the theoretical maximum resolution is about 68 LPPM.

The D700 has a sensor resolution of about 60 LPPM. The D800 sensor resolution is about 102 LPPM.

The standard system resolution formula is:

1/s^N = 1/a^N + 1/b^N

Where...

N= some number between 1 and 2, depending on your source for the formula. None of this is cast in stone with precision. For the example here I'll split the difference and use 1.5.

s = system resolution
a=component 1 resolution (sensor)
b=component 2 resolution (lens)

Doesn't matter which component has a given resolution- the formula does not care and treats each component equally and interchangeably..

(The above is only for those that want to check my math . The following is the important part; the conclusions suggested by the formula.)

As lenses go, 68 LPPM is not a very exciting optical resolution and that is why it is often said that by f/8 all lenses look alike. They should be stopped down enough to be as sharp as they are going to be and beyond that they just get softer as diffraction takes its toll.

At f/4 the maximum possible optical resolution is 186 LPPM. At f/4 you might be able to separate the men from the boys in terms of optical resolution. At f/2 the limit is 373 LPPM and if you can get a diffraction limited lens at f/2 you might have a very exciting lens . Good luck finding that lens .

With the D700 (or D3) you would get a system resolution of 40 LPPM assuming Perrone's old lens is diffraction limited at f/11. If the lens only delivers 50 LPPM you would get 34 LPPM.

Since the image resolution, as posted, is only equivilent to 22 LPPM, it doesn't require much of a lens to deliver that image as perfect as physics allows it to be. In fact, that lens might only deliver 25 LPPM (a very poor lens) and it would still provide a system resolution of 22 LPPM, theoretically a "perfect" image at this output size (in theory at least).

With the D800, if the lens is diffraction limited the resolution increases to 51 LPPM. If the lens is only good for 50 LPPM then the system resolution drops to 41 LPPM.

If you are still with me and haven't gone to the next reply or thread , you can see that with this image, which on a 100 DPI monitor is approximately equal to a 10x15 image displayed at arms length, not only is the D800 resolution higher than the D300 (with any lens) but regardless of the lens peformance (within reason) the system resolution of the image will always comfortably exceed the maximum res possible at this image size.

I think Perrone's image is helpful to demonstrate in real life why the world will not end at 36 mpx unless only the finest latest glass is used. The world will not end at f/7.1 either . At least not with a normal run of the mill print size .

If Perrone had wanted to illustrate the opposite- that only the finest glass will do, then he would have shot it at f/5.6 and shown us 100% crops, maybe verses the best glass he owns, also at f/5.6. I suspect then there might be a fair difference and putting the two images side by side, shot with very different quality optics, would highlight any differences..

And either way he would be "right", in the context intended. It really depends how big your "real world" is, in terms of output size.

All the numbers above are based on what I think are very questionable formulas, to the extent that the real world is not exactly modeled by simple formulas. And there are variations in the formulas, such as the value of "N". And the fact that that formula was based on a best fit of experimental results done long ago in the flm age.

That formula has never been verified with digital sensors (as far as I know) but there do not seem to be any replacement formulas. Just to say "trust your eyes", not the specific numbers that come out of these formulas. The value of the formula is to show, in a very general way, how resolution changes as either lens or sensor resolution is changed.


_________________________________
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 RE: There are two types of too close Neil.
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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 RE: I really don't see the relevance of this discussion...
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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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