I have this Takumar 200mm lens mounted on a Canon 60D with an m42 adapter. I really like the lens because of the bokeh it creates but the photos are so soft. I tried all the f numbers from 3.5 to 22 and see absolutely no difference.
The lens is very clear and there is no fungi, oil or scratch at all.
Here is an example photo taken with that lens, shooting conditions as below. I'm actually not sure about the shutter speed and aperture as the EXIF data seems not to be recorded correctly with this adapter.
Aperture: ? Shutter speed: 1/8000 ISO: 640 Daylight, handheld
If you open this full screen and zoom in you can see the image is soft all over even the rock/area within the focus range
I use my other Canon lens the same way but results are much sharper than this lens.
What makes the photos with this lens so soft? Is there any way to fix it? Would e.g. using it with a full frame camera help?