Dear dt colleagues, I have run into similar problems in the past. I do wildlife photography, often under impossible light conditions. I shoot in RAW + JPEG. The JPG exported from dt sometimes differs markedly in resolution and detail from that of the JPEG that the camera creates. I actually submitted correspondence to this forum about it, but because of clumsiness on my side in access to the images the message was never posted here. Here is the unposted message and a link to demo photos. Compression ration is definitely not the determining factor.
"I export many photographs to JPG as a format for sharing images with others. My Canon camera is configured to save RAW as well as hi-res JPG images. Images are 18 Mpixels RAW. Most of the time I manipulate the RAW image, export the final product to JPG and then use the JPG in communications with other people. Frequently, the JPG export from Darktable is MUCH more grainy than the JPG that the camera saves at shoot time. I use dt 1.1.1.2 on Ubuntu 12.10. If I edit the "native" Canon JPG file with GIMP, there is very little graininess introduced. Is there an explanation for the grainy exports from dt? " Kind regards, Willem Ferguson Link to demo photos: Hope this works. https://www.dropbox.com/sh/3n1gmle42s6p5cd/vV967SzKGO Kind regards, Willem Ferguson On 12/02/2013 21:37, [email protected] wrote: > Send Darktable-users mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > https://lists.sourceforge.net/lists/listinfo/darktable-users > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Darktable-users digest..." > > > Today's Topics: > > 1. Discrepancy Between Darkroom vs jpeg Export ? User Error or > Bug? (Ken March) > 2. Re: Discrepancy Between Darkroom vs jpeg Export ? User Error > or Bug? (Salvador Laiz) > 3. Re: Discrepancy Between Darkroom vs jpeg Export ? User Error > or Bug? (Ken March) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Tue, 12 Feb 2013 10:02:46 -0800 > From: Ken March <[email protected]> > Subject: [Darktable-users] Discrepancy Between Darkroom vs jpeg Export > ? User Error or Bug? > To: [email protected] > Message-ID: <[email protected]> > Content-Type: text/plain; charset="windows-1252" > > 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 > ------------------------------------------------------------------------------ Free Next-Gen Firewall Hardware Offer Buy your Sophos next-gen firewall before the end March 2013 and get the hardware for free! Learn more. http://p.sf.net/sfu/sophos-d2d-feb _______________________________________________ Darktable-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/darktable-users
