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Author Topic: Inverse choice in RAW development  (Read 7367 times)
Ernst Dinkla
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« on: December 17, 2016, 08:06:38 PM »

An exotic request it seems. Less so if you use the camera to copy color and B&W film negatives and like to use RAW tools (to some extent) to develop the images.  There are several ways to do this but all require the use of more than one application. For instance Vuescan can read CR2 files (DCraw based too) and export inverted linear Tiffs that can be imported in Photoshop ARC to get a kind of RAW development. MakeTiff + the Color Perfect plug-in for Photoshop is another route. Similar routes with Lightroom exist. RAW development tools are way easier to use when the RAW file is inverted. In fact RAW tools act properly on positive files. Sure there are ways to deal with it and I have done some direct conversions in QU on RAW files made from negatives with the camera.

I still wonder what the earliest stage of inversion could be in the development of such RAWs. I expect it has to be after demosaicing to ensure no data stew is made. Would it be possible to have most of the automatic interpreting functions of QU act after the inversion? Given the batch functions in QU it could be a convenient way to deal with a thousand CR2's like that.

Met vriendelijke groet, Ernst

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« Reply #1 on: December 17, 2016, 10:56:27 PM »

It's an interesting question.  In theory at least, the demosaicing should still work since it follows up/down trends and since ALL of the data was inverted, it would still work.  The problem comes in when you want to apply the white balance, tone reproduction curves, and the ICC profile: unless those are mathematically inverted, you'd get the wrong color in the end if you invert before those steps.

Ultimately, you'd want to get what the camera actually saw to look just like the negative and then invert as the last step.  Of course, that makes visual editing difficult: it might be possible to invert to a positive just prior to application of fill light, exposure, and other visual edits so that the editor could be used in a positive instead of negative fashion.  It might also work to invert at an early stage (say after WB and demosaicing), apply fill light, exposure, etc., invert a second time (back to negative) before applying the ICC profile, and then invert a third time to get the positive back at the end.  Fortunately no data loss is incurred due to inversion so you can invert as many times as you like without losing data.  To know anything more, I'd need some sample raws of negatives.

Mike
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Winfried
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« Reply #2 on: December 18, 2016, 11:36:16 AM »

Ernst, this request seemes not to be exotic. You can hardly buy an excellent film-scanner today. With the old once you run into driver problems (I know about VueScan, but is SCSI still supported on Win 10?).
I bought the "Pentax Film Duplicator" for digitalising slides, bw- and color-negatives up to 6x9cm film. And I am even able to handle pocket negatives (Typ 110) and the Kodak 126 negatives. I compared the quality with scans from a Nikon CoolScan-V ED and a CanoScan FS 4000 US. With my Pentax K-3 (24MP) I do not see real differences.  The quality depends of cause on the quality of the macro-lens.
I tried different workflows with Capture One Version 8, Pentax Digital Utility 5.6.2 and Rawtherapee version 4.2.135. For color film negatives I like most the workflow with RawTherapee. The WB automatic adjustment is nearly perfect. Of cause there is still some fine-tuning with a photo-editor necessary, because the colors of the negativs shifted during the time differently. Therefor you have to adjust the color-curves separatly.

Winfried
« Last Edit: December 18, 2016, 11:53:54 AM by Winfried » Logged
Ernst Dinkla
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« Reply #3 on: December 27, 2016, 03:24:19 PM »

It's an interesting question.  In theory at least, the demosaicing should still work since it follows up/down trends and since ALL of the data was inverted, it would still work.  The problem comes in when you want to apply the white balance, tone reproduction curves, and the ICC profile: unless those are mathematically inverted, you'd get the wrong color in the end if you invert before those steps.

Ultimately, you'd want to get what the camera actually saw to look just like the negative and then invert as the last step.  Of course, that makes visual editing difficult: it might be possible to invert to a positive just prior to application of fill light, exposure, and other visual edits so that the editor could be used in a positive instead of negative fashion.  It might also work to invert at an early stage (say after WB and demosaicing), apply fill light, exposure, etc., invert a second time (back to negative) before applying the ICC profile, and then invert a third time to get the positive back at the end.  Fortunately no data loss is incurred due to inversion so you can invert as many times as you like without losing data.  To know anything more, I'd need some sample raws of negatives.

Mike

Hello Mike,

The raws of color negatives are on their way to you by WeTransfer. I wrote a separate email to explain some aspects.


Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
November 2016 update, 700+ inkjet media white spectral plots
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