I was actually surprised at how much pretty much all Pentax lenses exhibit LoCA and in some cases purple fringing, but then I remembered that I was dealing with a 51MP camera, my old systems never broke 21MP so I was often ignorant of the fact that they actually had a lot of CA too, just with a lower magnification. In testing this out, I discovered that the 55/2.8 fringes about as much as my Canon 24-70 2.8 mkII, which I never though to have much fringing, but I never looked too hard into its IQ. For a relatively inexpensive, small and light lens, I really didn't expect much to begin with, but it can resolve the sensor for the most part at smaller apertures.
Unless you use some super "over-designed" lens, you probably won't get a razor sharp image, but the Pentax system doesn't yet seem to have any such lenses, although many people say the 90mm and 28-45mm qualify for that description. The 120mm macro is probably one of the most well-corrected lenses from the "old" glass, and even that has LoCA wide open.
Rather than making a set of super sharp and fast primes like Leica, Pentax is going the other way by first releasing various zooms, the 28-45mm is already out, so it leaves the 45-80mm and 80-160mm models, and maybe after that they'l begin refreshing primes, or perhaps bringing out new ones, but it'll take a few years to get there.
Originally posted by rcdurston Thanks everyone. I was looking for more real world experiences and examples. I'll need to rethink how I'm going to approach my current project instead. Might go back to 4x5 to get the look I'm going for, that won't be very spontaneous
I'll ask for a loan of the 90mm as well as see how it does.
Thanks again.
R
It's kind of hard to compare large format glass to anything else, especially if you can utilize the newer digital-optimized lenses, which you can cut steel with even wide open. It's one of the reasons why there are still people who would dish out 2-3x the price of the 645Z for a digital back with the same sensor in it that can be used on a tech cam.