Colors

Any digital image is represented by many individual pixels or cells that have different colors. The color in each cell is represented by a binary number.  The simplest digital image would have a single binary value for each pixel - so a pixel could be black or white. Fifteen years ago, this is most commonly all a computer would display on the screen. The early Apples and IBM PCs were monochrome (each pixel is a binary value).  Gradually, this has improved as the price of memory has declined.  There are a number of intermediate possibilities, based on the number of bits or binary values used to store the color for each pixel.  A monochrome monitor is one bit, a 16 color display is 4 bits, a 256 color display is 8 bits (a byte), a 65,536 color display is 16 bits, a 16,777,216 color display is 24 bits, and there is a 4,294,967,296 color 32 bit display.  For the present generation of digital cameras, they work fine with 24 bit color - for a camera with 3.4 million pixels, 16.7 million possible colors means that every pixel can be a unique color.  After digital cameras surpass the 16.7 million pixel mark, then there may be some advantage to 32 bit color.

You have no control over the color depth of your camera after you buy it - it is not an adjustable parameter on any camera on the market.  On the computer you use to edit and display your pictures, however, color depth is very important.  Looking at a digital photo on a 256 color display can be very misleading.  Trying to edit the picture at that color depth is almost certain to provide undesirable results.  This is because the picture has more colors in it than the computer display card can show.  It has to cram all the different colors into 256 possible buckets or colors, and video cards are not that good at color reduction.  Virtually any notebook or desktop manufactured since 1995 has the ability to display 24 bit color, so I would view it as a requirement for editing of digital photos.

If you publish your pictures on the Internet, one consideration is whether you should publish for the lowest common denominator.  The lowest common denominator in this case would be 256 colors.  If you are a professional web designer, then you know your target audience, and can make this decision based on the capabilities of your audience.  If you are an occasional webmaster or publisher, then I would strongly recommend only publishing your pictures in 24 bit JPEG format.  Within a few years, all browsers and computers will display this format, and it would be a shame to put a lot of effort into converting pictures to 256 colors, which does nothing to improve the appearance.  Your web pictures may have a long life - make them look nice and keep 24 bit color.