Since we're on the topic, I want to mention the CD produced by John Woods entitled "On Three: A guide to digital photography for cavers". In it, there's a great example of a many-layered digital image taken in Sequoia Crystal Cave. The room itself has several different light sources with a great variety of kelvin temperatures. There are several flash illuminated portions as well. Since this image was taken before RAW became the accepted format, the white balance was set before each of the images was captured. In any case, there are many different layers that have all blended together beautifully into a seemless image.
The CD explains and profusely illustrates all the techniques involved. Contact me at
pjcaver@gwi.net for more info the CD. Lots of great information about cave photography in general and digital cave photography in particular. See me at convention as well on Vendors Row.
Peter
pjcaver