Cameralabs D7100 review up: verdict...

Started Apr 19, 2013 | Discussions thread
photoreddi
Senior MemberPosts: 3,975
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Why I disagree with the verdict ...
In reply to mosswings, Apr 19, 2013

mosswings wrote:

http://www.cameralabs.com/reviews/Nikon_D7100/

In day to day shooting, the D7100 and D7000 and D5200 perform basically the same.  Noise is very similiar, the D7000 might have a bit of advantage at 100% at higher ISOs. Resolution wise, the AA filter appears to make no difference, echoing what DPR has said.  In tightly controlled studio shots we have seen differences, but that is not how people usually shoot. For the typical use case, one could argue that the removal of the AA filter is essentially a marketing feature.

While Cameralab has produced a decent D7100 review, it leaves some things unsaid and probably shares some of the flaws in DPR's reviews, especially where the studio images are concerned.

First, it must be said that the D7100 is to the D7000 as the D800 is to the D600 in that the DX crop area of the D800 pretty closely matches the pixel pitch and resolution of the D7100 and the DX crop area of the D600 similarly matches that of the D7000. So if the difference in resolution of the D7100 vs the D7000 is little to none, then the same should be true for the difference between the D800 and the D600. Maybe even more so, since unlike the D800, the D7100 has no AA filter.

Cameralabs said that the photos were shot using a tripod with f/5.6 for the aperture, but didn't mention whether mirror up was used or a remote release. They may have, but it would be nice if this could be known. If mirror up was not used and the self timer was used instead of a remote release, image quality would suffer at least slightly. Also unsaid was whether PDAF or CDAF (Live View) was used, and like many others I've consistently gotten more accurate AF using Live View.

Finally, DPR's studio photos can't be used to compare the D7000 against the D7100 because a smaller aperture was used, f/8 for the D7100 and f/9 for the D7000. This isn't the first time DPR has gotten things wrong in their studio photos. Some of their studio photos misreported the apertures used. They did this for the first go through of the NX200 when in their wisdom, a pentax manual focus lens was used with a lens adapter that didn't pass the aperture information to the camera. But even Cameralabs' use of f/5.6 was flawed based on Thom Hogan's comments in his D800/D800e review.

Here's the thing: certainly when we were at 12mp and lower we were living in a sort of Disneyesque world where everything was slightly sharper than reality. What do I mean by that? Diffraction wasn't getting fully recorded or seen in most cases. A D3 at f/16 was just starting to show visible differences on edges at 100% view for most people (though diffraction was already present, it wasn't clearly destroying edges enough for people to get upset). Some of this has to do with the way Bayer sensors record data. I've been saying for a long time that diffraction really only starts to be fully recorded by a Bayer camera when the Airy disc becomes about twice the size of an individual photosite. It's not a perfect predictor, since there's an optical system that sits above the photosite (AA/IR filter, which may have a waveplate in it, microlenses on the sensor itself). But it's been a "good enough" predictor for some time now.

So what do we see on the D800 and D800E? At and above f/8 diffraction is being fully recorded (at f/8 the Airy disc diameter is 10.7 microns, while the D800 sensor photosite implied diameter is a bit less than 5 microns). Even at f/5.6 the Airy disc is big enough to be producing clearly visible diffraction.

Okay, so what about the AA (D800) or lack of an AA (D800E)? Does that make a difference. At f/8 and above, not really. Diffraction is a worse sin than anti-aliasing, at least when you use the "visible" criteria. Technically, I measure a bit more resolution on the E than the non-E in these mid-range diffracted apertures. But looking at pixel views of images, the diffraction kills the edge acuity that the E normally provides you. I'm not convinced there's enough gain to warrant the difference if you're shooting at f/5.6 or above all the time. That shouldn't surprise anyone, considering that I concluded the same thing with a D3x (24mp) with and without an AA filter. In that case, the "without" was optical glass, with no fuzz/defuzz system like the D800E has.

Below f/5.6, things are completely different, and surprisingly so. From f/1.4 to f/4 the D800E has crisp, clean edges and is clearly gaining something from the lack of an anti-aliasing filter. But the D800 is different. While the D800 has what I would characterize as a weak AA filter (I've got plenty of moire examples from it, and can produce color fringing with it, too), it exhibits a different pattern than the D800E. From f/1.4 to f/4 there's a small but steady degradation of edges, almost like some form of weak diffraction were in play. That's actually entirely possible, as Nikon claims that there is a waveplate involved in the AA filter, and it may be the culprit.

So basically the conventional guess about who would want an E and who would want a non-E are exactly backwards. If you shoot wide open or near wide open with your lenses all the time (portraits, wildlife, sports, etc.) there's something to be said for having the D800E. If you shoot landscapes and are going for depth of field, diffraction will be your real enemy, not the AA filter.

http://www.bythom.com/nikond800review.htm

If this is true for the D800e it should also be true for the AA-less D7100. I can understand why DPR did their studio photos at f/8 and f/9. The 3D nature of the studio scene benefits from a wider DoF, but it does no favors to very high resolution, diffraction limited cameras. At least in DPR's D7100 preview that compared it with the D5200, the studio scenes were shot at wider apertures, and f/3.5 was found to produce the best results.

The samples below were shot at an aperture of F3.5. In repeated tests with the 50/1.4 optic, this gave the greatest amount of center sharpness on the D7100. At apertures wider than F3.5 and narrower than F5, we struggled to see any relevant differences in output.

http://www.dpreview.com/previews/nikon-d7100/6

DPR only provided the f/3.5 crops in the preview. It was clear that the D7100 provided more detail. It would have been better if DPR also provided comparison crops at f/4, f/4.5, f/5 and f/5.6 so we could determine for ourselves whether any observed differences were 'relevant'. Until some well heeled photographer here (not me) is able to do some tests using Nikon's "exotic" f/2.8 and f/4 telephotos showing that I'm wrong, I'm going to assume that at apertures below f/5.6 the D7100 will produce higher resolution photos than the D7000 and that it won't require struggling to see the differences.

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