Yashinon 50/2.0 and Rokkor-X PF 50/1.7, found rokkor's issue

[Arctures]

Hi everyone.

Last few days I have had some outdoor and indoor shots with both the M42 Yashica Auto Yashinon 50/2.0 and MD MC Rokkor-X PF 50/1.7. While comparing some shots from both the lenses I have discovered a conner sharpness problem Rokkor has. Is it normal situation with corner sharpness Rokkor 57/1.7 lenses have or do I have a crap copy? It does look for me that opposite side of the shot looks better. Some samples are as follows. Shown 100% crops of upper left corner:

Yashinon @ 2.0


Rokkor @ 1.7


Yashinon @ 2.8


Rokkor @ 2.8

[Mos6502]

You would really have to test with a flat surface, with all of the needles in different positions it's too hard to say.

[kyonthinh]

This has no connection with your lens problem, but your sensor is dirty i think.

[Arctures]

Hmm dirty sensor with Minolta lens only?

[kyonthinh]

I see all of them have a little marks in bokeh, i'm not sure why, maybe the sensor, maybe not.

[eno789]

First, I think the Rokkor lens you're testing should be either MC Rokkor PF 55mm f/1.7, or MC Rokkor PF 50mm f/1.7. There's no MC/MD 57mm.

The test is flawed, or at least the test method is not well explained. For the two, where did you focus on? Is the center sharp at all? It could be that you focus on different places, it could be curvature of focus plane.

I never worry too much about corner sharpness. I like my MC Rokkor 55mm f/1.7:

[Arctures]

Brian, thanks for mentioning, that is my mistake it's not 57 it is 50mm. But anyway it shouldn't have such corner IQ or not?

[Lightshow]

Try shooting more sample shots where it's easier to see detail, brick walls are ideal for lens testing though a bit boring.
Screen doors are also good.