Wide Histogram from Reindeer Graphics is a Photoshop plug-in that displays a wider image histogram (up to 1024 pixels wide) than Photoshop's own Histogram feature. The wider histogram resolves significantly finer tonality differences in 16-bit images, and the plug-in offers other enhancements, including histograms for hue and saturation and a luminosity graph with a legend bar that's delineated in Zone System values. The plug-in is free and compatible with Photoshop 5.5, 6, 7, and CS on both Windows and Mac. Reindeer Graphics offers several other interesting free Photoshop plug-ins at the same location.