Quote Originally Posted by Jos Segers View Post
Interesting because I use the lens very often. I was lucky to buy an almost new 67II, 165mm and 75mm as a set on the second hand market in the Netherlands for an exceptional low price. All items in new condition.
I am very impressed by the performance of the 75mm but would hesitate to use f4. To my understanding (Pentax 6x7) medium format lenses in general show optimal performance from f8 to f11? Is this lens in your opinion an exception? Are there any test reports available?



Do this:

Go out and take pictures. Take notes of corresponding photographs(f-stop, shutter speed, etc..)
When you find a photograph you want to make(I'd recommend using a tripod, just to keep the camera in the same position), find your exposure, and then close down(and moving shutter speed accordingly to keep the same exposure(1/4 @ f8 is the same as 1/15 @ f4, etc....)

Shoot from F2.8(wide open) down to F22/32, whatever the lens's smallest aperture is.
Move in full-stops, don't worry about 1/2f-stop movements.

Process said film(I'd shoot all 10 shots of the same thing, remember, KEEP NOTES!)

Scan/print said film, whichever way YOU do your post-processing workflow(analog or digitally).

Make your own comparisons. What works for joe-schmo in XYZ location might not work exactly the same for YOU in ZYX location, etc...

YOUR OWN EMPIRICAL DATA is CRUCIAL to YOU getting the most out of YOUR OWN equipment and film stock(s) of choice.