Originally Posted by wuther
And if you want to argue that jpeg even at high rates does not leave behind artifacts, well sorry but that is incorrect, jpeg is called lossy and has no lossless mode at higher settings. If that were true mid to higher end cameras would not have raw formats.
There is JPEG 2000 on my Paint Shop Pro which has a lossless mode but last time i checked i don't think you could use that for online images as it just will not display them due to browser recognition. The JPEG images can also have their chroma subsampling changed which does actually work well if you are trying to cut file size and finding red text backgrounds an issue.
Seriously though at very low levels of compression i do not think anyone even an expert photographer could notice the difference between a PNG file and a JPEG. Perhaps we should try some blind tests though and i'd be up for it.
Your digital camera must interpolate color, adjust for white balance, correct gamma, convert to a color profile, sharpen, and perform saturation and other adjustments before finally compressing the file into a JPEG image. A raw file is the pure data that comes from the camera's sensor. RAW is great for professional photographers because of all that but we are talking about taking an image directly off a Blu Ray disc and then compressing using JPEG at minimal settings so it's different to actually shooting an image in a camera therefore RAW is actually not relevant especially since Blu Ray is using 8 bit color so it's not even in the same class as a high end camera with regards it's color. Thats why i think using minimal compression for these Blu Ray stills and JPEG will show an image as good as PNG.
Indeed with a raw image, you can keep all of the color data, which means that you can push your edits further before you run into posterization, poor exposure, bad color depth, etc. Great for amateur and expert photographers.
Shooting RAW will capture between 10 and 14 bits of color per pixel while Blu Ray and JPEG match each other at 8 bits.