Ok, let's try to send this again.... > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bob Meyer > > From what I've read, I think many people have a misconception of what > RAW really is. I do not believe that a Canon RAW file is simply a > recording of the luminance info from each individual pixel. I've read > (and I can't remember where at the moment, but if I can track it down > I'll repost) that Canon's raw format is essentially a compressed > (lossless) TIFF file with some additional proprietary information > (primarily to carry the EXIF data and parameter settings used during > the shot), and an embedded jpeg for display on the LCD. (Even the 20D, > which writes a separate JPG file in RAW+JPG mode, still has an > embedded jpg within the raw file.) In fact, some of Canon's earlier > digital SLRs used the extension .TIF on their raw files.
I agree with you on all the items in your email. I am not sure what you suggest in the above paragraph, though. Are you saying that Canon actually stores all 3 color components for each pixel, i.e. they already interpolate the missing color information, and then store this image in a regular lossless compressed tiff format embedded in their raw files? I THINK this is not what Canon is doing. The reason is that the file sizes seem too small for this to be true. If you lossless compress a typical image the compression rate is usually less then 2 even when using fairly sophisticated algorithms. The raw files from Canon are considerably smaller then that even taking into account all the other information you mentioned above, i.e. SensorSize*12bits*3/Raw image size > 2. My GUESS is that Canon might use a compressed TIFF format on the luminance data for each channel, i.e. a gray-scale image and add all kinds of information to it. Basic processing like dark current correction, compensation for non-linearity, etc. is already done before the file is compressed. In any case, if you find that information about the Canon raw format I would be very interested. Regards, Robert * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
