I took a walk through our neighborhood with two objectives. One was to test my Industar 50 lens after I had re-lubed the focus threads with white lithium grease. The other was to pull together my conclusions about how to get the most from the combination of Kentmere 100 film and PMK Pyro processing.
I thought the lens performed very well. Focusing had none of the previous jerky, grinding movement. The black finish with white numerals make for nice contrast and the resolution seems as good as any of my Soviet-era lenses. Based on the first two digits of the serial number the black Industar 50 was manufactured in 1971, while the silver one dates back to 1957.
My understanding of the combination of Kentmere 100 film and PMK Pyro processing has been greatly enhanced by Rick Drawbridge's generous email responses to my inquiries about how he gets such consistently excellent results with the film and chemistry. Rick said that he follows the PMK processing instructions in every respect except one: he starts with the recommended 30 second continuous agitation, but then proceeds with just " two gentle inversions at the end of each minute thereafter."
That is quite a departure from the PMK instructions which everyone else seems to strictly adhere to of two tank inversions every fifteen seconds. Rick's time and temp in the PMK is eight minutes at 75F. Like pretty much everyone else, Rick shoots his Kentemere 100 at less then box speed; he rates "the Kentmere at 75 ISO for development in the PMK Pyro, and 400 ISO films such as HP5 or Tri-X at 200 ISO."
Based on my experience and the results shown by other users of PMK Pyro processing I think there is quite a lot of latitude available in regard to processing technique, but consistent and satisfying results likely depend on some careful experimentation. Choices in film speed rating, subject lighting, and scanning parameters all enter into the equation.
My own shooting style tends toward rather darker tonalities than Rick uses and I was happy in some respects with my intial guestimates of twelve minutes at 20C and fifteen second agitation intervals. So, I'll likely try some intermediate values between what Rick uses and the good results which others have come up with.
There are also some other film and processing combinations which I look forward to exploring. I have seen some very nice pictures made with Kentmere in Xtol, and Tri-X mated with PMK also looks very promising.