[cport]

If you prefer sharpness, go either to 12-24 or to samyang 8mm. 15 ltd is not as sharp but is so charming

[Dan]

If you prefer sharpness, go either to 12-24 or to samyang 8mm. 15 ltd is not as sharp but is so charming

The 15 Ltd is a tad sharper than the 12-24 if you use it stopped down to f/8, which is where I usually use it. When I say that it is a tad sharper, I mean across the entire field of view, assuming that you learn how to focus it properly. It's a different matter wide open, where the 12-24 is quite a bit sharper in the corners and along the edges (but not in the center). This is based on my experience with both lenses, but it can also be seen in the tests at Photozone. For example, these are the Photozone results at f/8 (MTF50 in LW/PH):

DA15 12-24/12mm /18mm (all at f/8)
2247 2126 2079 <Center
2086 2049 2018 <Border
1951 1933 1936 <Corner

Photozone: Pentax K Lens Tests

I find the 12-24 to be very sharp stopped down, and surprisingly sharp wide open. The problems I find with with the 12-24 are (1) the complex lateral CA, which is very difficult to correct in post processing, and (2) mediocre resistance to flare. The 15 Ltd has neither of these problems. I suppose you could characterize this as "charming"; I would say that the 15 Ltd has better rendering.

On the other hand, it is easy to produce soft corners with the 15 Ltd--even at f/8--if you are not careful in setting the focus point. Fortunately it is also easy to get the entire field of view sharp (at f/8) if you are careful. I did a lot of tests with my copy to determine the optimal focus point, and I now use scale focusing to set it at that point. You might think that this cannot possibly matter with a 15mm lens, but you would be wrong. The field curvature of the lens requires that you set the focus point carefully to get everything sharp. The 12-24 is easier to focus, because it has a flatter field.

The bottom line is that the 12-24 used to be one of my favorite lenses, but I rarely use it now that I have the DA15 Ltd.

Dan