Originally posted by normhead I find down to F22 to be useful on most lenses…. but at 28, f11 is probably all you need. Check your DoF guide. That diffraction is there on film as well, you possibly didn't notice because film is a naturally fuzzy process, but it was always there. With film, if you used large grained high speed film, one corner of a grain being hit by a photon would cause un-exposed areas of the grain to be developed. The only way to defeat that was to use a fine grained film, and then you had low ISO. lets not get nostalgic here. There were always trade offs. But then people were a lot less critical, images were often not viewed beyond 4x6 so f32 was acceptable. Reduce your image size to 4x6 on your screen, and it will probably still be acceptable.
The digital lenses should give you less Chromatic Aberrations and purple fringing. But older lenses are still quite useful. Use the forum lens guide. A bad lens from the film days is still bad in digital format. And an FA 31 ltd is still a great lens… you can't generalize…
Here's your lens…
SMC Pentax-F 28-80mm F3.5-4.5 Reviews - F Zoom Lenses - Pentax Lens Reviews & Lens Database
As you can see, there are quite a few lenses rated higher…. but people who own it like it.
Thanks for your pointed out. With my old Pentax I usally shot with f22 and I cannot say that the sharpness was less then using f8 or f4! The film was physically build and not digital as the sensor nowaday! All CMOS-sensor have a diffraction limit!
This limit cannot be exceed with lenses! So, the manufacturer of lenses tries to build lenses for "diffraction limit of a type of sensor"! But the Sensor manufacturer will push the maximum of the sensor out! So, we will have must lenses that no go with some sensor sizes!!!
I owned a Nikon D800 and no Nikkor digital lenses works very good or excellent with it! Only the very new Sigma 35/1.4 mm lens works great. I do think that Nikon will build new lenses for CMOS sensor with more then 24MP!
The K-3 works quite good with the "old" lenses. Very nice bokeh and sharpen enough! I do think that the M lenses from Pentax will works extremly good!
Your right the 31/f1.8 is a great lens indeed. All ltd lenses of pentax are awesome!!!
I do not give much of rating see in the lens database. Because the lenses were tested with different digicam with different sensor-type!!!! So, I do have to test myself with my K-3 to see what I have.
I read the review of the F 28-80. After that I would never use this lens an my K-3! And, I did it. The result is better then the review! So, I wish all to test yourself! And don't worry. Sometime you will have big surprise!
Last, almost rawconverter software can remouve chromatich aberration and purple fringing! That is not a reason to not use a lens!! And, every year all software are updated and works better!!!!