Convert x3f to gif Online: x3f2gif

You can use Tom's Editor to easily convert images from
Sigma Camera RAW Picture File .X3F to CompuServe Graphics Interchange Format .GIF.
Tom's Editor is a free, online image manipulation and converter program.

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X3F

Sigma Camera RAW Picture File is an image format with extension X3F.

GIF

GIF images were created by Compuserve. They can used no more than 256 colors and a single color transparenty (no Alpha channel). Today are rare since they offer low quality and huge filesizes. GIF animations are still in use.