GIFs are ideal for flat colour objects, and natural images that contain a fairly narrow range of tones. As the basic palette of a GIF is 256 colours, a complex image will ask Photoshop to bodge any intermediate colours.

One thing GIFs are definitely not suited to is handling gradients: these nearly always appear banded no matter how carefully you adapt the image. (In fact try and steer clear of long gradients altogether, as they tend to bring out the worst in people's monitors.)

Here's an example of how well GIFs handle flat colour

But someone with a 256 colour graphics set-up sees a considerably dithered image, such as the one on the right, which is the same image seen under 8 bits in Netscape.

Turning the graphic into a GIF, which uses a set palette instead of JPEGs inherent 16 million colours, forces Netscape to attempt to display the image with your original flat colours.

And you can squeeze a little more saved space out of that image by reducing the bit-depth still further. This is a 4-bit image (eg 16 colours). There's a little false colour where the image was anti-aliased when its size was reduced in Photoshop, but the quality is still quite acceptable.

However it's not quite that simple. Netscape still dithers most GIFs slightly, for a number of reasons such as the fact that the operating system it is running under grabs a few colours, so those have to be replaced, and the fact that if there are several GIFs on a page then there are more than likely more than 256 colours on a single page. And sometimes it just seems to dither things out of sheer spite.

To find out how to get round that, follow this link.

Related pages:

Introducing GIFs and JPEGs

JPEG examples

some non-Photoshop tricks for improving your Web graphics.

JPEG examples

Or:
back to the top

Page created by Jim Smith, May 20, 1996.