I guess my skepticism is it appears the AA filter was always blamed for loss of quality, suddenly it isn't any more.
Hi Wayne, Bernard,
And therein lies the crux. Yes there is some loss from the AA-filter at low contrast. An MTF curve shows that in general contrast will reduce as the detail gets smaller (higher spatial frequencies). When the subject matter is already of low contrast, then the resulting contrast will be lost to the noise floor and quantization accuracy (14-bit/channel in Raw, and 8 or 16-b/ch after conversion).
But with a bit of subject contrast, and a lens with good glare control and good enough MTF helps, there will be enough micro-contrast left to come close to resolving all the way up to the physical limit, the Nyquist frequency. That Nyquist frequency is determined by the sensor's sampling density (the sensel pitch).
Probably because it keeps the distance between the mount and sensor exactly the same between the D800 and D800e?
It's the sensel pitch that makes the difference. When the same optical projection is sampled at the same sampling pitch, there will be no difference in resolution (usually expressed as a spatial frequency in cycles/mm). The only difference will be in the amplitude of the signal at the same spatial frequencies. The AA-filter is designed to reduce the amplitude as the spatial frequencies approach the Nyquist frequency,
in order to reduce the signal amplitudes beyond Nyquist. It's those spatial frequencies beyond Nyquist that cause aliasing, so when the amplitudes of those details (that are too fine to resolve reliably anyway) are reduced, then there will be no aliasing.
When the same optical projection is sampled at a lower density, then the resolution will be lower. The only way to compensate for that is to use a longer focal length to magnify the projected image. When we then add more sensels to increase the Field of View again, then there will again be no difference in resolution (because the output magnification can be proportionally reduced). There will be a better signal amplitude (the '3-D' look). And that's exactly the difference with Medium Format cameras and backs. They tend to have a larger sensel pitch, and need a longer focal length to cover the larger image circle with more sensels.
OF course, the other thing that I"m curious about is the camera doesn't have an "aa" filter per se, the filter they are using isn't exactly the same as having no AA filter. I'm not sure why you bend the light only to "bend it back" ... why not just leave it off? I really can't understand why this concept is better.
I agree that bending the light only to "bend it back" doesn't seem like an efficient operation. I'm not so sure that that is what is actually happening, I also don't understand how it could function as descibed in their marketing diagrams. So there is possibly something else going on, but Nikon decided to not change the number of plane parallel surfaces and thicknesses in the lightpath.
That could help to make optical lens designs which incorporate the existence of those surfaces and layers, and deliver a better image quality, they become part of the optical design. BTW, it probably one of the reasons that Leica didn't use AA-filters either because, added to the proximity of the exit pupil to the sensor surface, the lenses are designed to deliver an image to film, without additional optical elements in the lightpath.
I'm not necessarily disagreeing with the test, as I've felt for a long time that well done sharpening seems to compensate pretty well for issues like an AA filter or diffraction. It just seems the target introducing moire biases the results.
Well, that's a matter of opinion. The target doesn't
introduce(!) moiré, let's be clear about that. It only allows to make it visible, which opens the opportunity to devise a remedie. I'd rather be aware of a potential issue, than be confronted in the midst of (or even worse, after) an assignment.
Moiré can only manifest itself when 2 sampling grids are out of sync (by rotation or frequency). The sensor array is a given sampling grid, so if we can avoid shooting repetitive structures then we won't have 2 grids that are out of sync. When we reduce the amplitude of one of the grids (the projected image), the moiré will be less visible (e.g. diffraction or de-focus, or an AA-filter). When we use a longer focal length to magnify the subject details the aliasing will be reduced because of the relatively denser sampling of the projected image details (but also our FoV is reduced, so we need to stitch or use a larger sensor to compensate).
An interesting exercise would be for a D800E owner to shoot the target with a good lens at say f/4 or f/5.6 and, without changing focus, at f/16 or f/22, which may be what a landscape shooter would like to do to achieve the DOF required. The higher modulation of the D800E will help, and the aliasing of sharp edged detail is reduced by diffraction, and diffraction can be reasonably well deconvolution sharpened to restore resolution, but without aliasing artifacts, and the low noise images which the camera is capable of will allow more severe deconvolution sharpening.
Cheers,
Bart
