Incident angle can aggravate the difference in stack thickness. 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.
snapsy wrote:
Here's a comparison with the Sony 20-70 f/4 @ 20mm f/4. This lens doesn't exhibit the edge softness of the 20mm f/1.8, which even at f/4 shows edge softness on the Z7 vs A7rIV.
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.
snapsy wrote:
Here's a comparison with the Sony 20-70 f/4 @ 20mm f/4. This lens doesn't exhibit the edge softness of the 20mm f/1.8, which even at f/4 shows edge softness on the Z7 vs A7rIV.
