Re: [CinePaint] jpg worse
Bob Friesenhahn <[email protected]>
| Newsgroups | gmane.comp.video.cinepaint.user |
|---|---|
| Message-ID | <[email protected]> |
On Fri, 14 Mar 2008, Rob Lingelbach wrote: > > then perhaps I've got my signals crossed- I thought a camera RAW file > was essentially without compression, whereas a JPEG file, even when > set to 100% quality factor, still had compression, which can be seen > particularly in a repeating pattern. It is true that camera RAW files are not compressed in the traditional sense. However, it can be seen that the camera's use of a Bayer pattern is indeed a form of compression (just as YCbCr with subsampling is for video). The major advantages of RAW are its complete preservation of dynamic range, and avoiding slow and power-hungry post-processing within the camera. For natural scenes, it is difficult to find visible evidence of JPEG artifacts for reasonable JPEG compression levels. If the image is processed several times and saved as JPEG each time, the artifacts will become more apparent. That is why saving to JPEG should be the last step. The biggest problems noticed with JPEG compression are for non-natural computer renderings with sharp features such as text. Digital cameras with the Foveon sensor (http://en.wikipedia.org/wiki/Foveon_X3_sensor) are quite interesting since they entirely avoid the artifacts caused by "Bayer" compression. Close inspection of images produced by the Foveon sensor shows considerably more precise detail. The complete lack of distortion down to the pixel level (other than contributed by the lense) is a bit startling. Bob ====================================== Bob Friesenhahn [email protected], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/