For a planet whose brightness averages magnitude —2.5 (exceeded only by Venus), Jupiter can be surprisingly difficult to photograph well. Its small size demands the use of eyepiece projection and exposures of several seconds, during which seeing conditions may blur fine details.
Jupiter's limb is significantly
darker than the center of its disk. While this is not obvious to the eye, it is readily detected on film. In images processed for high contrast (to reveal belt and zone details), the limb regions can darken and merge with the sky background.
Astrophotographers resort to a few darkroom tricks to get around this difficulty. One way is to expose a print for the limb regions and burn in (give more exposure to) the center of the disk—or inversely, hold back the limb by using dodging (reducing the exposure). Another trick is to sandwich the negative with a slightly out-of-focus positive image. This "unsharp mask" can reveal wonderful details.
While many beautiful color photos of Jupiter have been taken, most planet photographers prefer to use black-and-white film, usually Kodak's
Technical Pan. It offers fine grain, good contrast control, and costs less than color. With an f-ratio of about f/60, try exposures of 1, 2, and 4 seconds.
Many astrophotographers are now switching to CCDs, despite the high initial costs
. The main reason is that electronic imaging affords greater flexibility in processing. Software offers unsharp masking and many other enhancements, all at the click of a mouse.