A bit of perspective...
Hi,
Aliasing was always a part of medium format. Please do remember that essentially all MFD cameras lack OLP (Optical Low Pass) filters, with the exception of the early Kodak backs and the Mamiya ZD that offered an OLP filter as an option.
Combining a good lens with relatively large pixels is a sure recipe for aliasing. But, aliasing yields fake detail instead of true detail. That is the reason it is called aliasing. It converts high frequency detail that the lens transmits into low frequency aliases.
The reason that photographers don't object to aliasing is that it is not very obvious, unless it shows up as color moiré.
Now, for some reason I don't really understand, Fuji claimed to have reduced the pixel aperture on the GFX 50S/R. Any point of the image is smeared out over the pixel aperture, so a small pixel aperture increases contrast at the pixel level, but it will also produce fake detail. So, Fuji essentially choose pixel level contrast over correct reproduction.
Now, we don't know if other vendors have used the same trick. But, wait a moment...
Reducing the pixel aperture means that the pixel collects less light, doesn't it.
Now, let's look at the DPReview test images for the GFX 50/S, GFX 100, Hasselblad X1D and the Phase One XF/IQ 3100MP combo:
We can see that both 50 MP sensors show a large amount of aliasing, while the 100 MP backs are almost aliasing free. Note also that the X1D shows more aliasing than the GFX. That would indicate that either the 90/3.2 lens on the X1D is much sharper or that both use similar pixel aperture.
Reducing pixel aperture significantly would reduce quantum efficiency, leading to longer exposure, but both the X1D and the GFX 50/S use the same exposure f/8 and 1/20s.
Comparing raw exposures for the GFX50S (DSC3041.RAF) and Hasselblad X1D (B0000401.3FR) we can see that there is not a huge difference between G channels:
So both are about 1.4EV under saturation, with presumed saturation at +3EV.
SNR is essentially the square root of the photoons captured.
GFX 50S has SNR = 6821 / 56.9 -> 110
X1D has SNR = 28375 / 236 -> 120
So SNR is pretty close and it seems that the X1D got slightly more exposure (relative saturation). But the differences do not indicate a huge difference in pixel aperture size.
The great unknown here is of course if DPReview uses a variable light source. Their description of the protocols used could be more comprehensive.
My take is really:
- MFD users like aliasing, as it gives an impression of sharpness.
- Fuji with the GFX is obliging by using relatively small pixel apertures.
- The Hasselblad X1D gives similar amount of aliasing as the GFX 50.
Jim's investigation shows that the GFX 50/S has higher MTF at similar cy/mm than the GFX 100. So the GFX 100 obviously has smaller physical pixel aperture than the GFX 50/S. So the GFX 100 has no more acutance than the GFX 50/S, but resolves finer detail.
I always said that both the GFX 50/S and the X1D cried for a higher resolution sensor. Jim's findings show why!
Best regards
Erik