Originally posted by Pentaxor hmmm...comparing two different lenses are quite tricky especially if one is a zoom lens. personally I won't just rely on the exif for focal length equivalence but would look at the images on the viewfinder for exact focal length comparison. you can use the focal length indicator on the lens as a starting point and make the necessary adjustment from there. use the prime lens first as your basis for focal length.
it would be also advisable to use a tripod. in this scenario, it is better to shoot at proper exposure for both lenses rather than have to adjust. also, you need something with a better and a definitive background, subject shot from equivalent mfd for both lenses to infinity for the background. this is a bit of work, but atleast the tests would be more reliable.
as far as the samples are concerned, bokeh don't seem to be different due to the difference in focal length distance. one seems to be short of 5mm (2nd pic). sharpness seems to be sharper on the 2nd pic as well, although this is a bit hard to judge since they don't have the similar focal length distance. I would assume the 2nd pic would appear better if the focal length distance are identical.
Lol, thanks for the tips, guys. I do know most of the facts you mention, and perhaps I should have guessed there would be criticisms despite the disclaimer of "quick and dirty".. I guess I was a bit excited after seeing the impressive results. Just a few explanations for what it's worth:
1. I dislike flash intensely for indoor shots. I also wanted a clean image which was the reason for ISO200, which then meant that to get a fast enough shutter speed, I had to underexpose. I can do this knowing K-5's dynamic range.
2. Regarding focus speed asked about, I believe the favourable comparison is to other SDM lenses, not internal focus motor of K-5. Additioanally, there is an even bigger gap when using live view contrast detect.
Despite the failings of my test methods, I think the lens does extremely well against a prime..