-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Harman Bajwa
--- "Schlake (William Colburn)" <[EMAIL PROTECTED]> wrote: >> The Canon jpeg settings are poorly choosen. A high >> quality jpeg from >> the camera or software corresponds to a 100% JPEG >> group conversion. >> Those settings aren't harmful to the image, but they >> basically turn off >> jpeg compression, so your image is huge with no >> quality gain over a >> lower setting. >Correct me if I am wrong, but JPEG is all about >"Lossy" compression - the lower the compression >quality, the higher the loss of information in the >picture (leading to artifacts, etc.). Now at 100%, the >loss may be minimal but there should still be some >compression - a difference which shoudl be measureable >by saving the same image as a bitmap (RGB - no >compression) and comparing the file sizes. The bitmap >should still be bigger than a 100% quality JPEG. >Another proof of this is that at for all files at 100% > (with the same dimension) the file should be exactly >the same - which is obviously not the case since the >file size will vary depending on the scene complexity >even at 100%. There is a lossless JPEG but it works differently then the JPEG most people are familiar with. Actually, I am not aware of any camera that supports it. The fact that files do not have all the same size is no proof that the compression is lossy. A good and familiar example is zip. If you zip a text file you get a much higher compression ratio then when you compress a binary file yet both are compressed lossless. I have no idea what the 100% setting does on Canon cameras. If it does set the quantization coefficients to 1 (i.e. no values are modified) then depending on other factors the compression can be almost lossless short of some rounding noise from the cosine transform, color conversion, etc. Nevertheless, as you said JPEG never guarantees to be lossless. Robert * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
