Anyway, after the upgrade, I was poking around online for tutorials to learn how to use some of the new features, and found that Adobe had released something called the Lens Profile creator, which can be downloaded for free at http://labs.adobe.com/technologies/lensprofile_creator/. The program comes with a selection of PDF files which are black and white checkerboard patterns of different sizes (grid size and block size). Ideally, Adobe recommends (for a prime lens) at least nine different photos at each of three different distances at three different apertures each. Yes, this amounts to one heck of a lot of photos.
I decided to give it a whirl, because I've been using my wide angle lens a lot more than I used to lately, and much like most lenses of this type, there's a bit of vignetting (darkening) around the edges, and I really hate how straight lines get pulled, especially in the corners.
After a trip to Kinko's to have the largest grid printed (my printer can only handle up to 13" wide paper), I went into my studio space, and set up the first of the grids on a piece of foamcore (also from Kinko's) on an easel, and set up a pair of daylight balanced fluorescent bulbs equidistant from the board, and at 45 degrees to it. After about an hour, I downloaded everything to the computer and got started.
First off, if you're going to do this, one word of advice, WATCH YOUR EXPOSURE. because the grids are black and white, getting your camera's exposure meter to read everything correctly is tricky (it works on to try to get the mid point to match an 18% gray card. Since there's no tonal midpoint in these grids, it will likely get confused). Also, I had found some instructions somewhere that led me to believe that before you get started, you can make any normal raw adjustments before you import the photos into the program. Unrortunately, I found that if you're working in raw, for some reason, the profile creator WILL NOT look at the sidecar file. So after I got everything imported, and set up, I let the computer do its thing, for six hours! I think a lot of that time was because the exposures were a little less than optimal on a number of the photos.
one of the photos from the mid-distance group- notice that the lines aren't parallel to each other- this is normal with a wide angle lens.
So after all was said and done, I saved the lens profile, and got back to work. Here are a couple versions of the same photo from my Philadelphia trip, before and after applying the lens profile, with no other adjustments made:
I love how the vignetting is gone, and now the lines are much straighter.