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Camera vs PC DNG Conversion?

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Camera vs PC DNG Conversion?
« on: 26 / March / 2009, 18:25:04 »
Have been searching the forum concerning camera vs PC DNG Conversion but have found nothing.

Did I miss anything?

If there is nothing has anyone tested to see if there is a significant difference?




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Re: Camera vs PC DNG Conversion?
« Reply #1 on: 26 / March / 2009, 18:36:00 »
pc dng - compressed dngs. camera dng - uncompressed. quality is the same. in camera dng contains some different exif values, but should more or less be the same.

Re: Camera vs PC DNG Conversion?
« Reply #2 on: 04 / April / 2009, 07:12:50 »
A difference with the DNG4PS-2 I noticed it is the different sampling: DNGs in camera (as the CHDK raw are 10-bit array) instead the denis' DNGs are 16-bit file..
This is easy to notice even watching the different size of the DNG files (I'm talking in both cases of uncompressed file, obviously ;) ) and there are subtle difference in the istogram and colors when opened in the raw-converter (I prefer work on an already "translated" to 16-bit file as RT work in a such space and to avoid internal conversion).
Furthermore with DNG4PS-2 there is even the possibility of compression that makes anyway a more little output rather than the 10-bit (uncompressed) DNG in camera.. ;)

Re: Camera vs PC DNG Conversion?
« Reply #3 on: 05 / April / 2009, 16:25:40 »
Hi Chelidon,

Thanks for your comments!

Was especially interested in "I prefer work on an already "translated" to 16-bit file as RT work in a such space and to avoid internal conversion"

Question:  Since RawTherapee will open CHDK RAW files are you using these or are you 1st converting them to DNG using DNG4PS-2?

Thanks again


Re: Camera vs PC DNG Conversion?
« Reply #4 on: 07 / April / 2009, 14:17:57 »
RT support the CHDK raw as soon as dcraw does, but since the deconding engine (based on dcraw) it is changed only version by version, the newest CHDK camera aren't perfectly supported (coloured dominant are possible) so in this cases it is better using DNG. I prefer using DNG4PS-2 because, about what I know, DNG are normally 16-bit standard file (I suppose DNG brought by CHDK is something like a 10-bit CHDK raw transposition with a DNG header because of time processing issues) and as I said RT work in a 16-bit CIELab color space.. Thus if I send to RT directly a 16-bit file I will avoid (possible) time consuming conversion and approssimations broght by the many Post-Processing operations (Actually RT should make the conversion from 10 to 16 bit and then applies operation, but I assume it's better simplify the process upstream to avoid surprise..)

Anyway you can test on your own the difference: making a photo with CHDK in DNG (1- so you have a CHDK DNG), then converting DNG to CRW with the CHDK proper function (2- so you have a CHDK raw file) and then sending the CRW to DNG4PS-2 (3- so you have even a "real" DNG). Lastly you can compare the three different files and notice what I describe before (obviously you may open these file with RT or any other software) ;)
« Last Edit: 07 / April / 2009, 14:19:33 by Chelidon »


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