On 13-Nov-10 21:37, Trevor Cunningham wrote:
David Dyer-Bennet -- Skinner Memorial Chapel (east face) at Carleton College -- Good to point out the curves element. The fringe on all of the edges is a little too electric (cyan/magenta) for my liking. I get this a lot with my Nikon. I wonder what causes it.
Sorry about the CA! I don't really have the habit of looking for it, but there are a couple of spots in this picture where it's kind of obtrusive, even to my eye, when I do look. Looks like -14 cyan/red does about as well as can be done (in ACR, anyway).
I would expect it to be more lens-related than camera-related generally; and this is a cheap lens with exotic specifications, and an ultra-wide, which are particularly hard to design CA out of. But how many places can you buy a 12mm full-frame lens for less than a grand? (Sigma 12-24mm f/4.5-5.6 full-frame, for those not wanting to go look up my notes on the photo in the gallery.)
One of my "great insights" (they're greatly helpful to me, at least) on use of the curves tool (which is the single most important tool for photo prep) was that what you're essentially doing is dividing up the contrast range and allocating it to different areas of the brightness range. If you want the middle highlights to be more contrasty, you have to make some other area less contrasty! In this case, there was a good-size zone in the middle with very few pixels in it, and I just stretched the darks up into that zone, and brights down into it, opening both up considerably, with no real loss in this case.
Sometimes that's good enough, and sometimes you need to "cheat" and use HDR or at least masking and multiple curves layers.
-- David Dyer-Bennet, dd-b@xxxxxxxx; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info
