[Digikam-users] Re: need advice re: format conversion

[Gilles Caulier]

2011/1/18 Tom Cloyd <tomcloyd at comcast.net>:
> I have close to 2000 *.CRW raw files (Canon format) and am accumulating
> a number of *.JPG originals from a Nikon camera I've just been given.
> After studying the Digikam manual a bit, I'm unsure what to do about
> conversion of originals for storage.
>
> I find that converting the CRW to DNG is easy, but the resulting image
> (preview, at least) is washed out, and thus not good for previewing to
> decide about image quality relative to the possibility of doing further
> work on an image. Is there a way to get a better preview image for the
> DNG conversion?

I recommend to try 1.7.0 release where DNG converter have been
improved by Jens recently.

>
> With the *.JPG originals, I find no advice in the manual. Should I just
> store the original JPG? If I convert to PNG, I get huge files, and my
> storage costs go up.

PNG is lossless compression based on LZW. It's not optimum for photo.

digiKam support JPEG2000 and PGF format. Both are based on wavelets
compression which are really better. There is a lossless compression
option. Both give better compression ratio.

JPEG2000 is very slow due to use floating point computation. It's also
patented format.
PGF is the opensource alternative to JPEG2000. All is computed in
integer. It's very fast, as JPEG.

http://en.wikipedia.org/wiki/Progressive_Graphics_File

Both format support metadata preservation. both can be used for
archiving purpose.

PGF is new format, not very well supported outside digiKam. JPEG 2000
is better supported, but, it's JPEG2000.

I plan to add WebP format support in digiKam in the future, the famous
Wavelets/Theora based image format for the web. But for the moment,
libwebp is not clear about licensing, and format need to be supported
better in metadata framework. I wait and see..

> I'd convert to DNG but I don't see how to do this
> in Digikam (yet). Is this even [a] advisable - for long term storage,
> and [b] possible, as a batch conversion in Digikam?

It's not possible to convert JPEG to DNG. DNG is to store raw image
data, not demosaiced image array.

Best

Gilles Caulier

>
> Thanks for the help, in advance. Continuing to have a great time with
> this program.
>
> Tom C.
>
>
> --
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> "Sow a thought and you reap an action; sow an act and you reap
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> and you reap a destiny." ~ Ralph Waldo Emerson (1803 - 1882)
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Tom Cloyd, MS MA
> Private practice Psychotherapist
> St. George, Utah, U.S.A: (435) 272-3332
> <<  tc at tomcloyd.com>>  (email)
> <<  TomCloyd.com>>  (website)
> <<  sleightmind.wordpress.com>>  (mental health issues weblog)
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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