Hi Salvador,
Thank you for the very good question!
I exported to jpeg @ 88% compression, AND reduced the size to 2048 width
(from 4716). The export is as a local file, (versus some on-line
repository such as picasa, etc.).
So I just now experimented with the export options, including 1) jpeg
compression levels (88% versus 100%), 2) the size (reduced to 2048 width
versus full size), and 3) format, (jpeg versus png).
I've posted the results for everyone to see, here:
http://flic.kr/s/aHsjDXTttt . (Note that the PNG files are only
available in the "original" size file download.)
In that same directory is the darktable screenshot, as well.
It appears that there is a discrepancy between the darktable screenshot,
and all of the exported files.
I'm curious to know if I can prevent this discrepancy.
If the answer is no, then is it predictable, so that I may work around it?
Ken
On 02/12/2013 10:17 AM, Salvador Laiz wrote:
Have you taken a look at the jpeg quality export options? Is it at
100% quality?
2013/2/12 Ken March <[email protected]
<mailto:[email protected]>>
Greetings!
Currently I'm editing 28 very noisy sports photos. They were all
shot outdoors under a heavy cloud cover, late in the afternoon
near dusk, at 1600 ISO and a slow lens (F5.6 to F5.0) on a 15
mega-pixel camera, (Canon 500D).
After I edited, and exported 4 of these photos to jpeg, I noticed
differences between the noise in the jpeg files versus what is
seen in darkroom.
I'm new to darktable, so I'm wondering if this might be user error!
For one of these files in question, I have a screen-shot of what
darkroom displays, as well as the jpeg, xmp file, and originating
cr2 file available here,
https://www.dropbox.com/s/2wb2p3zzqokpnqg/denoise-differences.zip
(~22MB). (First time sharing via dropbox, so let me know if I've
screwed it up.)
For reference, the denoise tools that I've implemented are:
1. raw denoise – threshold 0.01, blend mode unbounded, opacity 100%
2. demosaic – amaze, edge threshold 0.003, color smoothing 2
times, match greens full and local avg
3. denoise (non-local means) – patch size 3, strength 100%, luma
50%, chroma 100%, blend mode unbounded
4. sharpen – radius 2, amount 0.5, threshold 0.5, blend mode off
The differences are subtle, but exist. In particular there are two
things I've noticed:
First,the noise seen in the pavement in the foreground and of the
bumper sides around the lower portion of the karts is smoother in
darkroom (as seen in the example screen-shot) than as seen in the
jpeg. The zoom level is 1.5:1, btw.
The second discrepancy is that in the jpeg there a couple of light
dots on the leading kart's bumper in the area in front of his rear
wheel, which are not seen in the darktable screen-shot.
Why is there a discrepancy between what is seen in darktable
versus the exported jpeg?
(I hope the answer is user error! :-) )
It will improve my work flow to understand this discrepancy.
Kind regards,
Ken
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--
Un saludo,
Salvador Laiz
fulgacian - View my most interesting photos on Flickriver
<http://www.flickriver.com/photos/fulgacian/popular-interesting/>
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