Yes, exactly. More information is more bytes --- it's not just more
details. Noise are details, for the math processing; and a blocked
shadow will compress better than a detailed one.
For the compression factor, all depends on the algorithm. Most often
than not, the quality facto 0-100 maps only to a handful of ratios (I do
not know what the darktable jpeg engine is doing, so I can't say more)
Look at http://regex.info/blog/lightroom-goodies/jpeg-quality , it's
quite interesting.
Romano
On 25/03/16 16:31, Jean-Luc Coulon (f5ibh) wrote:
Hi,
This(more details = bigger files) is true *if* you do the same
manipulations from a RAW and from a JPEG.
BUT Canon doesnt do the same kind of process with JPEG developped in
camera (you can only play with few parameters - e.g. sharpening,
saturation, contrast, and noise reduction).
The worse for the filesize is often the ISO value. If you increase the
ISO value, you raise the noise. And noise, as being random data,
doesnt compress very well.
In the RAW developper, imagine you raise the shadow (which otherwise
would be mostly black). Black would be well compressed in jpeg. But if
you raise the shadows, you will get more tones (and noise in these
tones also, remember, you have only few discrete tone value in low IL)
and there will be less compression.
Try to developp a RAW without using any fancy module.: only the WB,
the curve. And see the size you will get. But, anyway 96% or 98% are
only some values for comparison : 98 > 96 :)
Jean-Luc
2016-03-25 15:40 GMT+01:00 Romano Giannetti <[email protected]
<mailto:[email protected]>>:
On 25/03/16 11:12, Bernard wrote:
[...] Using Darktable, I expect to obtain from the Canon raw
files, better JPGs than those produced by the camera and, most
of all,
in modifying, rotating, sampling, cutting etc... from CR2s, I
expect not
to loose quality at each re Saving as this happens with lossy
jpeg files.
Yes --- you have a lot less of quality (details) loss manipulating
raw file than jpeg.
And as a consequence, you have more information in your images, so
Problem is... those jpg files that I obtain from an export
process in
Darktable, are more than TWICE AS BIG as those delivered by my
Canon
Camera
...you need more bytes to memorize that information. ;-)
TANSTAAFL:
https://en.wikipedia.org/wiki/There_ain't_no_such_thing_as_a_free_lunch
<https://en.wikipedia.org/wiki/There_ain%27t_no_such_thing_as_a_free_lunch>
Romano
--
Romano Giannetti
http://www.rgtti.com/
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--
Romano Giannetti
http://www.rgtti.com/
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