Nothing as long as the exposure and color balance are perfect.
Everything if they're way off. The subject picture was underexposed
enough that it's not possible to adjust the exposure to the right level
without introducing a small amount of posterization into the image.
With only 256 integer brightness levels available in a JPEG if the
brightness is increase by multiplying by, say, 1.5 then a brightness
level of 100 becomes 150. But so does a brightness level of 101 become
150. The distinction in original brightness levels between those two
pixels has been lost. A certain amount is acceptable but after a point
it begins to look like a poster painted with not enough colors. You may
also lose pixels at the bright or shadow ends where multiplication or
division of the brightness value simply rounds them off to pure black or
white.
The 12 bit raw image and later conversion into 16 bits for processing
give you a lot more leeway in adjusting brightness, contrast, saturation
and color balance which are all things that affect the brightness levels
of individual pixels.
Chuck Norcutt
Tim Randles wrote:
> what is wrong with JPEG format?
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