tsdevine wrote:
Incident angle can aggravate the difference in performance. So it is possible that you see different degradation between the 20 G and 20-70 G. If the light is directed at a steeper angle on the 20 G towards the edges and corners, compared to the 20-70 G @ 20......there can be a larger impact to a thinner stack when you compare the two lenses. Again, what I said above though could make sense, if the lens design of each lens has a different incident angle as the image is being projected onto the sensor.
That's part of the reason that "some" lenses can have degradation that was noted in that article you linked to. The wider the lens, often the steeper the incident angle. But even within wide angles there can be variations in the design, it can be worse on some than others. And faster lenses need larger front elements, so they often have higher incident angles as a result. The longer the focal length, the incident angle may not be as high just by the nature of it being a telephoto.
I believe what I described is a plausible reason for what you are seeing, but I have no way to prove it.
These lenses are highly optimized for the bodies they are supposed to work on. When you know even a tiny tilt in lens mount can impact IQ, I'm not that surprised of your results. As long as it works great on Sony bodies, I don't really care, to be honest.
This is dissapointing to me personally. As part of a light weight kit, an AF UW with a stellar IQ, Sony 20/1.8G was the candidate. Now back to research mode. I may just settle with Nikon 20mm /1.8S
Someone there asked how the 20mm f/1.8 performs if I focus via the left edge instead of center. Here's what the left edge looks like when focus is done there vs focus performed on the center:
Definitely disappointing to me, I was thinking of picking up a Sony 20mm f1.8, Sigma 20mm f1.4. or Sigma 14mm f1,4 for astro this summer. Sounds like at least 2 of those 3 might be out.
Are you using the Megadap ETZ21 or ETZ21 Pro? I wonder if there is a slight thickness issue with the adapter. When going from Nikon to Sony I definitely learned an adapter to short, or even worse an adapter slightly to long will cause issues especially with wide angle lenses towards the edges.
I think the Nikon camera may be applying a lens correction profile from some other lens based on its communication with the adapter. This was a common problem with some of the first "smart" Canon EF to Fuji GFX lens adapters.
The disparity in cover glass thickness often introduces some level of field curvature. That's part of the reason it ends up looking soft.
snapsy wrote:
I started a parallel thread on Dpreview here.
Someone there asked how the 20mm f/1.8 performs if I focus via the left edge instead of center. Here's what the left edge looks like when focus is done there vs focus performed on the center:
The text below is more directed at snapsy, not you molson....but your comments spurred mine.
Is there a way to turn all corrections off in camera on the Nikons? On Sony, distortion correction doesn't impact RAWs. Shading correction does affect RAWs as does CA correction (not sure about that one.)
Ideally you want the Nikon RAW file to be "RAW" sans any corrections and then when you go into Lightroom, assuming that's what you're using, Then in Lightroom you can turn corrections on and choose the Sony 20/1.8 G profile.
molson wrote:
I think the Nikon camera may be applying a lens correction profile from some other lens based on its communication with the adapter. This was a common problem with some of the first "smart" Canon EF to Fuji GFX lens adapters.
tsdevine wrote:
The text below is more directed at snapsy, not you molson....but your comments spurred mine.
Is there a way to turn all corrections off in camera on the Nikons? On Sony, distortion correction doesn't impact RAWs. Shading correction does affect RAWs as does CA correction (not sure about that one.)
Ideally you want the Nikon RAW file to be "RAW" sans any corrections and then when you go into Lightroom, assuming that's what you're using, Then in Lightroom you can turn corrections on and choose the Sony 20/1.8 G profile.
Yes, you can turn off the lens corrections in the Nikon cameras - vignetting, diffraction compensation, and distortion control.
molson wrote:
I think the Nikon camera may be applying a lens correction profile from some other lens based on its communication with the adapter. This was a common problem with some of the first "smart" Canon EF to Fuji GFX lens adapters.
When I read your post my immediate reaction was "no way". But I checked the raw and sure enough the Z7 is embedding a lens correction profile into the raw file, which must be coming from the Megadap.
Here's a comparison I did with and without the lens correction profile applied - the without case is done by stripping the correction profile from the raw via exiftool:
molson wrote:
Yes, you can turn off the lens corrections in the Nikon cameras - vignetting, diffraction compensation, and distortion control.
On some lenses you can, others you can't. For Nikon's native lenses they typically preclude you on the consumer-level lenses or those with lots of corrections, for example the 24-70 f/4. I checked for the Sony 20mm f/1.8 with Megadap and ACR/LR does not let you disable the profile, so you have to strip it from the raw before importing to render without it.
snapsy wrote:
On some lenses you can, others you can't. For Nikon's native lenses they typically preclude you on the consumer-level lenses or those with lots of corrections, for example the 24-70 f/4. I checked for the Sony 20mm f/1.8 with Megadap and ACR/LR does not let you disable the profile, so you have to strip it from the raw before importing to render without it.
Interesting... even if the distortion control is set to "Off" it automatically turns it back on when I attach the 24-70mm f4S.
I think with Sony lenses like the 20-70 G and 24-105 G they don't ever really let you "turn off" distortion correction in camera. But the RAW file is truly the RAW file.....and the correction profile is embedded and it's turned on automatically in Lightroom. For other lenses you actually can turn it off in camera, and it's really off...like it's off even when looking through the EVF.
With Canon lenses using Sigma's adapter, it says that the built in profile is applied, but I can always pick the actual profile for whatever lens I'm using.
For the consumer grade Nikon lenses that sort of force correction to be on...can you turn it off in Lightroom to see the true uncorrected view? Or is it sort of forced on in Lightroom too?
molson wrote:
I guess if they didn't do this with the consumer-grade lenses, they would get too many complaints about the lenses.
tsdevine wrote:
I think with Sony lenses like the 20-70 G and 24-105 G they don't ever really let you "turn off" distortion correction in camera. But the RAW file is truly the RAW file.....and the correction profile is embedded and it's turned on automatically in Lightroom. For other lenses you actually can turn it off in camera, and it's really off...like it's off even when looking through the EVF.
With Canon lenses using Sigma's adapter, it says that the built in profile is applied, but I can always pick the actual profile for whatever lens I'm using.
For the consumer grade Nikon lenses that sort of force correction to be on...can you turn it off in Lightroom to see the true uncorrected view? Or is it sort of forced on in Lightroom too?
