My maternal grandmother had strawberry-blonde hair in her younger days (I've seen colour photos of her when she was young) but when I tried to colour her mother's hair that colour, it just didn't look right. Too light. Auburn? No, that didn't look right either. I asked my mother, but she had no idea. Great-grandma was a white-haired old lady by time my mother came along.

The only thing I could do was just to play about with colour sliders until her hair looked "right". That's when I made a profound discovery: my great-grandmother's hair was brown - like mine! It was only colour that looked natural.

My great-grandmother and I never met, but thanks to Photoshop, I now have a better idea of what she looked like than would have been possible just from a black and white photo.

.bmp Windows bitmapped image. Used by Microsoft Windows applications. Good quality, large file size. Not for use on web.

.wmf Windows MetaFile. Useful for clipart, and can be used to make large area, small sized background files.

.pcx Older general purpose format. Practically obsolete now. Not for use on web.

.psp Internal format for Paint Shop Pro, useful if you want to swap files between these two applications.

.pcd Kodak PhotoCD format, used with Photo Developing - although most photo processors will save your photos as jpegs if you ask them to.

.pdf Portable Document File. Adobe's file system that allows electronic cross platform sharing of documents.

So what's best format for web graphics: gif or jpeg?

The general rule of thumb is to use gifs for diagrams, line drawings, illustrations, and images that contain large areas of flat colour, and jpegs for photographs and images with continuous colour tones. The jpeg format has a very good compression rate, but compression reduces quality of image, so it's best to experiment with tools in Image Ready until you have optimal quality/file size. The gif format, on other hand, has a smaller file size - but a limited range of colours.