Yashica Vs. Pentax Vs. Sigma

One of my Photography buddies recently acquired a screwmount Yashica 28mm f2.8 lens. While I was arrranging to purchase a zoom from him (more about this later) he asked me if I could/would play with it and test it out. Always eager to play with another lens I said sure. This is my first try at a controlled test. I did OK with setting up lighting, but I think I had one flaw with my methodology, in that I used the focus confirmation indicator in my camera to confirm that the two manual focus lenses were focused. I think somehow that the Yashica focused a little toward the front of the subject, while the Pentax was spot on. The Sigma 17-70 I had the camera focus the first shot then switched to Manual focus mode, assuming from chimping the LCD that it was correctly focused, I think it also was slightly front focused as well.

I will try to post a few 100% crops later to show the differences, but you should be able to see which was the sharpest from these shots.

I shot all lenses at wide open (f3.5 for the Pentax k-28mm f3.5 and the Sigma 17-70, and f2.8 for the Yashica 28mm f2.8.) with the Sigma zoomed to 28mm. Then at f4, 5.6, 8, 11, and 16. Except for minor differences in color, all were quite sharp at f11 and f16. At f8 they were all reasonably good with the Pentax slightly ahead in sharpness. The Pentax was by far the best performer at f3.5 (wide open). The Sigma tended to overexpose which I think compromised it's IQ a little bit as well.


Yashica f2.8 Yashica f4.0

Yashica f5.6

Yashica f8

Yashica f11

Yashica f16

Pentax f3.5 Pentax f4.0

Pentax f5.6

Pentax f8.0

Pentax f11

Pentax f16

Sigma f3.5 Sigma f4.0

Sigma f5.6

Sigma f8

Sigma f11

Sigma f16