Wednesday, April 25, 2007

"For the Love of Light"

Jim Austin's article on high-dynamic range (HDR) photography, "HDR For the Love of Light", features my work "Hamilton Pool Panorama no. 2". Thanks for the kind words, Jim, and the excellent article. Anyone who wants an introduction to high dynamic range photography, or impressive examples of its use, will find that article worth a look.

Ironically, I recently discovered a problem in my panoramic workflow that has been muting the colors in my work for some time. Most of my panoramas, including that one, need to be recomputed to bring out the true quality of their color. I'm in the process of doing that in between work on my ongoing Spring panorama project at the Bamberger Ranch Preserve. Unfortunately, recomputing the panoramas, and then processing them as HDR, is very time consuming, so I don't expect to have everything fixed any time soon.

To elaborate on the problem, Apple's Aperture application, which I use for managing my photos (when it works, it's great; when it doesn't, it reminds me of Photoshop), has a preset export option labelled something like "Original Size, 16-bit TIFF". Because that was the only preset export option that suggests that it preserves all of the information in RAW originals, and because Aperture is designed for professional photographers, I naively assumed that it would also preserve the color space of the images. Not so. In fact, it converts the image to the sRGB color space, a big step down from the AdobeRGB color space of my originals. This isn't a bug, but I do think the name of that preset export option should be changed to something that makes its behavior explicit, like "Original Size, 16-bit TIFF, sRGB".

Once I noticed that problem and fixed it, I was bit by another. I needed a utility that would let me assign a color space to the non-color-managed 16-bit TIFF images produced by the software I use for assembling panoramas (PTMac). I tried doing it with Photoshop CS, but it launches so slowly that it created a strong incentive to find a lighter-weight tool for this job. (Aperture, frustratingly, provides no mechanism for assigning a color space to an image.) After a bit of Googling, I found an article in Apple's "Pro" area titled "Image Editing in ColorSync" which told me that Apple's "ColorSync Utility" was precisely what I was looking for. I started using it, and, for a while, I thought it was a great tool. Then I realized that when it saved my 16-bit TIFFs with their newly assigned color spaces, it was saving them as 8-bit TIFFs. Put simply, this "Pro" tool was automatically throwing away half of the data in my images without a single word of warning. I'm still dumbstruck by this behavior. And there's no way around it; while its "Save As" dialog offers an enticing pop-up menu that allows the image bit-depth to be specified, the only option it offers is 8-bit.

So, I'm back to Photoshop for my color-space assignment needs. (Sigh.) If anyone can suggest an alternative color-space assignment tool for Mac OS X, please do.

No comments:

Post a Comment