Bill Tuthill added these comments in the current discussion du jour
....

In rec.photo.digital harrogate3 wrote:

JPEG is a lossy form of saving the picture -

The Bayer sensor is already lossy, having only one of RGGB at
any of four pixel locations, so one could make the argument that
JPEG imposes no further loss.

Google on 'explanation of jpg' and it will give you the detail

or read
http://photo.net/jpeg/learn/

Bill, I'm not nearly enough of a mathematicion to understand this,
but it is WAY over the OP's head. Might it be better to describe
the issue in more qualitative than theoretical ways he can
understand?

--
HP, aka Jerry