Highlight Tone Priority
Anhinga Many of Canon's newer DSLRs contain a feature called "highlight tone priority" (HTP). Canon claims this feature will help to prevent you from overexposing the highlights of your images. If you enable this feature, you'll see a D+ appear on the panel of your camera. I'm always concerned about retaining detail in the highlights of my images, so I decided to find out how this feature works and test it out to see if there's any improvement to the image quality of my photographs. Here's how it works. Your exposure is determined by three factors: shutter speed, aperture, and ISO. Once you (manually or using the automatic features camera) determine the proper exposure, your camera lowers the ISO setting by one stop, effectively underexposing your image. This is why when HTP is on your minimum ISO is 200. This of course will also underexpose the darker portions of your photograph, so the camera brightens the darker portions so that they will m...