I wanted a street photography lens that didn't immediately identify me as a block photographer. Even my 50mm f/1.4 lens was larger than I wanted. I was talking about buying the limited edition Pentax originally introduced, but didn't want to pay the price. This lens was 2/3 cheaper, was made for a different market, but works well with both my K-5 and K100D Super. It doesn't have a "Quick Shift" function to switch to manual mode, but I can't think of a case where I would use it in manual focus mode. Focus speed on my K-5 is near instantaneous and with negligible noise, despite what I've read, especially since in a street photography app all portraits are taken from roughly the same distance. Focus is not heard. Focusing is also very fast with the K100D. As soon as you press the shutter button halfway, you have focus lock (provided you have decent contrast, of course). The minimum focusing distance is 0.4 meters, which is quite suitable for my purposes; mainly street portraits at a distance of about 1 meter, 30 - 40 inches and more. The bokeh is at this distance and f/4 is good as I will show later. Some initial test shots show that it's very sharp in the center and pretty good towards the edges at f/4, which is where I'll be using it most of the time. I'll try to get some shots this weekend and post them along with the shots I just took to show the amazingly thin profile of the K100D. I'm also planning to use this lens with one of my K100D Super cases in a minimalist permanent system in the smallest shoulder strap case I can find. This and the street photography app is its niche I think for my camera bodies, although I also understand that it was introduced to a different market and Pentax camera system. One downside that others have identified is the snap-on lens cap. To me it's almost a ridiculous silence. Ideal for use in a camera bag. Out of the box I use an inexpensive 27mm UV filter which is easy to replace if it ever gets scratched - and I've never been able to scratch it. So it's not an all-round lens by any means, but to create a system in such a small form factor while retaining all the flexibility and control of a DSLR, I felt the price was justified.
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