Dynamic Point spread function of Hiro's Zeiss APO135 F2 at F2.5
I got an opportunity to analyze Hiro's image using the Zeiss 135mm F2 APO sonnar shot at F2.0
I used Pixinsight's Dynamic PSF to get an idea of the star shapes in a somewhat objective fashion.
I selected several stars from each of the image corners. This is usually a very severe test and hardly any lens I have used produces results higher than around 0.50 in r value. (the ratio of greatest length to smallest width)
The Zeiss produces results in excess of 0.80 everywhere on the frame, often even higher than 0.90.
The results at F2.0 interestingly aren't much worse, they are still in excess of .80 across much of the frame.
I compared this with an image from the Tak FSQ at F5. The result with the Tak was similar: just a smidge lower even! But the APO sonnar stars are much smaller as expected for an F2.0 scope.
Dynamic Point spread function of Hiro's Zeiss APO135 F2 at F2.5
I got an opportunity to analyze Hiro's image using the Zeiss 135mm F2 APO sonnar shot at F2.0
I used Pixinsight's Dynamic PSF to get an idea of the star shapes in a somewhat objective fashion.
I selected several stars from each of the image corners. This is usually a very severe test and hardly any lens I have used produces results higher than around 0.50 in r value. (the ratio of greatest length to smallest width)
The Zeiss produces results in excess of 0.80 everywhere on the frame, often even higher than 0.90.
The results at F2.0 interestingly aren't much worse, they are still in excess of .80 across much of the frame.
I compared this with an image from the Tak FSQ at F5. The result with the Tak was similar: just a smidge lower even! But the APO sonnar stars are much smaller as expected for an F2.0 scope.