thanks man. very helpful
The format supports up to 8 bits per pixel for each image, allowing a single image to reference its own palette of up to 256 different colors chosen from the 24-bit RGB color space. It also supports animations and allows a separate palette of up to 256 colors for each frame. These palette limitations make the GIF format less suitable for reproducing color photographs and other images with continuous color, but it is well-suited for simpler images such as graphics or logos with solid areas of color (Source)
OK guys, you've convinced me. I'll keep the original png format. If I want gif then I can convert it.
GIF is fine for many things, just not especially designed for the millions-of-colours palette that modern computers use.
Actually, the ideal format for screenshots is JPG, since it produces smaller files. PNG is just a more-advanced GIF, and its chief advantage (as with GIF) is a built-in transparency channel -- but this isn't used for screenshots.
GIF images are compressed using the Lempel-Ziv-Welch (LZW) lossless data compression technique to reduce the file size without degrading the visual quality. This compression technique was patented in 1985. Controversy over the licensing agreement between the software patent holder, Unisys, and CompuServe in 1994 spurred the development of the Portable Network Graphics (PNG) standard. By 2004 all the relevant patents had expired.
For those with a fear of Terminal, myself included, I neglected to mention that there several utilities that can change the format of screenshots without relying on Terminal commands. In Onyx this feature is found in Parameters>General. IIRC Tinker Tool and several other utilities can make this change.Sorry about that. Thought I had saved the link. Here's the info you need.