BrightnessCopyright 2009 Matt Mortensen
OK, so that last post got me thinking, maybe not everyone understands what I mean by "pure" yellow. Furthermore, many of my friends don't know what that histogram on their digital camera means. It is not necessary to know these things to get good pictures, but you will get more consistent results if you do. I am going to start with 'brightness' or as it is sometimes called, 'value'. Brightness is what your histogram is telling you about and in an 8-bit JPEG image it can have values between 0 and 255. In the image above, the brightness varies from 0 on the left to 255 on the right. I removed all color to avoid distraction. Why that little histogram on your camera is so important is because any pixels that fall outside 0-255 have no information and thus you have not captured the full scene. Not to worry, brightness is the easiest value to change in photography by adjusting exposure time. As long as the scene you are photographing does not have really high contrast (more on this later), you should be able to get those pixels away from either end. One more thing...what we normally consider a "good" picture has areas of both pure black and pure white somewhere in the scene. If you get a histogram that does not stretch to the edges it is normally good to stretch the contrast later on the computer. Good luck!
