RustyBug wrote: nehemiahphoto wrote:
an APO lens with SA.
Wake me up when you find it ... just to make sure I wasn't dreaming.
There aren't many APO lenses with some residual uncorrected SA but it is not as though they don't exist. One clear example is the Zeiss Otis 28 f/1.4. I had this lens and it is huge, but had wonderful rendering. Wide open at f/1.4 it has, IMO, a nice amount of uncorrected SA, but stopped down just 2 stops the lens is amazingly sharp across the field at f/2.8. You can see that in the MTF charts here:
At first/1.4 the field is pretty flat with rather lower astigmatism, but the contrast levels are about 92%, 78%, and 52% contrast at 10, 20, & 40 lp/mm respectively. This level of performance is not unsharp, but it is not as though they corrected for all the spherical aberrations either. Those MTF charts match my experience with the lens as well.
You see a similar situation with the Zeiss ZE/ZF/Milvus 135 f/2 APO. Note this lens has zero aspherical elements, and this lens too has, IMO, after using it a fair bit some uncorrected spherical aberrations wide open as well. You can see that in the MTF charts here:
Wide open the lens has a very flat field with almost no astigmatism, but the contrast levels are about 92%, 82%, and 61% contrast at 10, 20, & 40 lp/mm. Again the level of performance is not unsharp and just a little sharper than the Otis 28 at f/1.4, but it is not as though the results are totally corrected for spherical aberrations either. The performance, just like the Otus is much higher a couple of stops down, and is notably below several other fast 135mm lenses.
I really like these two Zeiss lenses for their performance, but they are both very large. I would love to see smaller APO lenses that perform more like these two than APO lenses that go for the highest possible sharpness such as the Leica SL APO summicrons. I like it when a lens is a bit less sharp wide open than what it is a couple of stops down.
Jan 09, 2025 at 12:27 PM
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