New to forum, so if I missed this already being revealed please excuse me. Back in the late 60's when in Vietnam I purchased a Spotmatic and many prime lenses, from the standard Super Tak. 50mm to a 300 mm. Very,very, cheap then, even at a Corporals wages. I used these for many years with film. These lenses sat in a case for many years, after going digital with some point and shoots. I was waiting for prices of a full frame Pentax DSLR to become reasonable. I did purchase a original Pentax M42 adaptor.
Well, couldn't wait any longer, just bought a K70. I'am now amazed how sharp and fast these Super Takumars really are.. After re-setting up settings to manual, finding the Tv-shift under the e-dial programing was the most difficult. I use the Av mode and the ISO locked at 400. That way, when I rotate the aperture ring I can watch the shutter speed change in the viewfinder. And, do not have to use the green button. So merely, focus, press shutter to see speed then rotate to 1/500, for action, and take pix. In normal daylight, this is around f5.6, a good sweet spot for the f2.5 135 mm. I use the most. With the 1.5 conversion, this equals a 200 mm telephoto. On my wildlife shoots, I can normally just leave lens at f5.6, stay focused on moving beast, and snap away.
Something I have not come across yet, is the anti-shake setting for a M42 should it be the full frame mm or the 1.5 compensation? I have been setting it at 200mm, for the 135mm, and doesn't seem a problem.
Super Takumars; f4 17mm, f3.5 24mm, f1.4 50mm, f4 50mm macro, f2.5 135mm, f4 300mm.
Read more at:
How to use/meter Manual & M42 Lenses on all Pentax DSLRs (K-1, K-3, K-5, K-30, etc) - Page 22 - PentaxForums.com