Originally Posted by
Jon Ruyle
I didn't know it was modified. How? Why?
When one shoots wider than f/2.8, Canon mangles the raw data with a digital push in order to compensate for lower sensor response to light from oblique angles due to the microlenses. You can read about where it's done in the 30D here, but Canon didn't fix it for the 5D2, and I doubt the 50D or 60D will be corrected either:
http://www.pages.drexel.edu/~par24/rawhistogram/CanonRawScaling/CanonRawScaling.html
The reason they do this is for all the same reasons as above. Papering over the sensor angle of response with a digital push helps Customer Service issues (people don't wonder why their f/1.2 is darker than f/2.8), Marketing, Management, Beurocracy, etc. Of course, if you slightly untwist the lens so that there is no electronic communication, then the camera will not know to apply the push to your f/1.2 or f/1.4 lens, which allows you to get the unmodified raw data. There's really no good reason to mangle the raw data IMHO.
Originally Posted by
Jon Ruyle
A friend of mine is always going on about how someone should make an open source camera.
That would be really great. CHDK is a stellar example of what can be done even when Canon is fighting to prevent it. And here I would have thought a legion of unpaid programmers adding tremendous new features would be a good thing.
If Canon open sources their firmware, I will add the metadata ISO feature myself.