AWB still OWB

[stunsworth]

Originally Posted by Alberti

...the JPEG sizes do seem to change from e.g. 3.5 Mb to sometimed 7-8 Mb after some tweking. The only way I can think this happens is by stuffing extra bits in the process somewhere

Hi Alberti, Jpeg size will depend on how easily an image can be compressed. So for example a noisy image will almost always be larger than the same image with noise reduction added. Jpegs are always 8 bits per channel, so there are no extra bits to be stuffed in.

Sorry if you knew this already <grin>

[fefe]

You can see this kind ofdifference at the same ratio of compression if a soft image was sharpened a lot. JPEG compression comes from cutting low spatial frequency informations from the image and sharpening just creates a lot of high frequency spatial information that will go above the threshold set in a "high quality jpg" quantization.

Most blocks of the soft image that would have been highly compressed (with info loss) just end up being compressed by the lossless part of jpeg (which doesn't compress that much).

It has happened to me only with relatively soft landscapes where sharpening extracts a lot of high frequency spatial info (leaves/grass) at relatively high quality settings of jpeg.

[Alberti]

Originally Posted by stunsworth

Hi Alberti, Jpeg size will depend on how easily an image can be compressed. So for example a noisy image will almost always be larger than the same image with noise reduction added. Jpegs are always 8 bits per channel, so there are no extra bits to be stuffed in.

Sorry if you knew this already <grin>

You are right of course but I will make some tests in changing colours (resetting the OWB) without changing sharpening. Then provide some statistics, the earlier ideas were a hunch but easily falsified. alberti