>-----Original Message----- >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Ken Durling > >OK, I'm full of questions today. Can someone explain briefly whether >or not there is any direct connection between megapixels and megabytes >under any circumstances? Like a X megapixel camera shooting at >maximum resolution? It seems clear that cameras with larger >megapixel specs produce larger files, but is it linear in any way?
No, there is no direct connection between MPixels and MBytes for all possible circumstances. For instance some cameras store images with 8bits/channel and others at 10, 12, etc bits/channels. For example if you have a camera with x Mpixel and each pixel has 8-bits/channel then you will get x Mbytes uncompressed data. If the camera stores 12 bits/channel then you will end up with 1.5*x Mbytes uncompressed data, etc. In some special cases there might be even more bits for the green channel then the other two channels. Also sometimes other color filters are used. Now the above is just for uncompressed data. This is valid if the camera stores uncompressed data as is sometimes the case with raw and tif data. I believe to remember that Canon's digital cameras compress raw data (without any loss). In that case the final size depends on the picture. Nevertheless, often jpeg compression is used. The quality settings usualy determin the quantization table used. The lower the quality setting the higher the quantization steps are. If you had a picture that contains exactly the same color everywhere (which won't happen in practice) then the compression ratio will be extremly high even for the highest quality settings. If you use a lower quality settings the jpeg algorithm considers small variations as a constant color which will result in the infamous 8x8 blocking artifacts and loss in details. This is very apperant in uniform areas like a sky, etc. Other compression algorithms, i.e. jpeg2000 are better able to retain details for such highly compressed images. So in short, there is no direct relation between MPixels and MBytes as it depends on to many factors as the type of images photographed, the compression used (if any), the bits/channels, etc. Robert * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
