[Emacs]

but beyond f5.6 the 31 would win due to diffraction issues on the FF.

Diffraction is less visible on FF due to lesser "magnification". It's sigma 50/1.4 that is optimized for wider apertures and thus sacrifices a bit of IQ when stopped down or just your sample.

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Last edited by Emacs; 05-21-2012 at 01:36 AM.

[Emacs]

There is someone making exactly the opposite argument in the Photokina thread in News&Rumors.

I guess that was a joke. Because the purpose larger sensors are used for is to minimize optics impact on the output, they "hide" little lens rendition imperfections with lesser magnification.

[bossa]

Diffraction is less visible on FF due to lesser "magnification". It's sigma 50/1.4 that is optimized for wider apertures and thus sacrifices a bit of IQ when stopped down or just your sample.

It obviously depends on the viewing situation to a degree. And I wasn't speaking about 'my copy' in particular.

[Emacs]

It obviously depends on the viewing situation to a degree.

It doesn't depend on "situation": X times linearly larger sensor, X times less noticeable diffraction.

[bossa]

It doesn't depend on "situation": X times linearly larger sensor, X times less noticeable diffraction.

This is how I think about it and I'm not saying I am 100% correct about this:

1. Smaller pixels and a high density show more diffraction.
2. Larger pixels and a lower res sensor would show less.
3. A hi res APS-C sensor would also show more diffraction.
4. Lenses have a lot to do with it as well
5. Most lenses reach their peak around f/7 to f/8 after which diffraction starts to become more noticeable.
6. I don't know how much the actual size of the sensor has to do with it rather than the resolution of said sensor.

[Emacs]

6. I don't know how much the actual size of the sensor has to do with it rather than the resolution of said sensor.

Final output. The only thing that matters is the final output. You need to enlarge more for the same size output with lesser sensor. When you enlarge, diffraction spots are getting bigger as well.

[bossa]

Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks

[Blue]

I doubt that diffraction is going to really limit a 50mm on 36MP FF until about f/11, based on some of the lens data I've seen. You'll start to see diffraction take effect after f/5.6, but the 36MP sensor will still resolve more than the 16MP sensor even after the effects of diffraction past (probably) f/8, possibly up to f/13.

Below is the 50mm f/1.8G on the 12MP D3 vs. 24MP D3x - notice how the diffraction-limited 24MP sensor still outresolves the 12MP sensor's peak performance (the d3 + 50 peaks at f/5.6) until about f/13... the 31ltd on a 16MP sensor is going to have a different curve, but it almost assuredly won't be able to start out-resolving the 50mm on a 36MP sensor by f/5.6 already.

On a related not, based on what I saw at Nikon, the new flagship ff, D4, will have a 16.2 mp sensor instead of the 24mp the D3x had. That was an interesting move given the 800 has the 36 mp.

D4 Digital SLR Camera | SLR Digital Cameras

I guess that was a joke. Because the purpose larger sensors are used for is to minimize optics impact on the output, they "hide" little lens rendition imperfections with lesser magnification.

No, it isn't a joke. There are those including, that thread, that argue that Pentax will need all new lenses to go ff because the film lenses were designed for film.