need advice re: format conversion

[tomcloyd]

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?

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. 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?

Thanks for the help, in advance. Continuing to have a great time with
this program.

Tom C.


--

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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a habit; sow a habit and you reap a character; sow a character
and you reap a destiny." ~ Ralph Waldo Emerson (1803 - 1882)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tom Cloyd, MS MA
Private practice Psychotherapist
St. George, Utah, U.S.A: [phone]
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[Sebastian Schubert-2]

Hi,

I suppose you mix up something. crw and dng are RAW files, ie, they
include the full information from your camera's sensor (that's why
they are so big). A real picture in the sense of a jpg, png etc has to
be calculated from that. There is (a) no one to one correspondence,
ie, there are different approaches how to do that, different algorithm
and (b) you loose information on the way (which is not bad or better,
necessary, because you want to look at the picture). So there is no
way to get a RAW from jpg (well, I guess you could somehow get a raw
by guessing some data but that would not make any sense).

On Tue, Jan 18, 2011 at 5:41 AM, Tom Cloyd <[hidden email]> wrote:
> 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?

Why do you want to convert them to dng? Just keep in mind, that there
are some raw converters which cannot work with dng. The preview of the
dng might look washed out because the preview might be calculated from
the raw itself, while the native canon raws include a preview jpg made
by the camera, where contrast is increased and sharpening is applied.
This does not mean raw is bad, you just have to make sure, that some
post-processing is applied.

>
> 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. 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?

Why do you want to convert? First it's not possible to convert to dng
because of the reasons mentioned above. jpg is a lossy format. In
principle, if you open the jpg FOR EDITING (not for viewing) and save
it to another file, you loose information. By repeating that, you
loose more and more information (bad). On the other hand, png is
lossless compression. You don't loose information when saving it. So
if you plan to edit the jpg severals time, than a conversion to png
and then editing them might a good idea. However, if you have the raw
of the picture, I would work with the raw, because it's much more
flexible. The result can then be saved in a jpg (for viewing, that's
fine if you take a good enough jpg quality).

I hope that helps,
Sebastian
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[Gilles Caulier-4]

2011/1/18 Tom Cloyd <[hidden email]>:

> 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
> a habit; sow a habit and you reap a character; sow a character
> and you reap a destiny." ~ Ralph Waldo Emerson (1803 - 1882)
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Tom Cloyd, MS MA
> Private practice Psychotherapist
> St. George, Utah, U.S.A: [phone]
> <<  [hidden email]>>  (email)
> <<  TomCloyd.com>>  (website)
> <<  sleightmind.wordpress.com>>  (mental health issues weblog)
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
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> 2011/1/18 Tom Cloyd <[hidden email]>:
>> 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.

why don't you archive the jpg as the original file? you probably can't
acheive better compression.

jdd

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Sebastian, Giles, and jdd - thanks to you all for your useful responses to my query about formats to which to convert for archival storage of original camera images. In general, my questions derived directly from reading the Digikam manual.

Some responses -

*** Sebastian wrote: "Why do you want to convert them to dng?"

Well, at http://docs.kde.org/development/en/extragear-graphics/digikam/dam.html#best-practice I read:
"RAW are converted to DNG and stored away into an RAW archive"... and
"rate and cull, write-back metadata to the DNG archive"

So, DNG is spoken of as the archival format of choice for raw camera files. Elsewhere (same page???) in the manual it is mentioned that proprietary raw camera file formats come and go, but DNG is more likely to be readable by software in the distant future.

I was therefore thinking that I should be converting my hundreds (about 2000) of *.CRW images to DNG. I'm certainly open to other good ideas, but that was what my reading of the manual led me to believe.

Sebastian, your comments lead me to think that camera JPG images should just be stored as such. Of course, images produced by digital processing I do are another matter...(see below).

*** Giles -

I looked at compiling the 1.7.0 release, but stopped when I saw that not only must I compile it, I must also compile several of the dependencies. I wish I had time to pursue this, but cannot at this time. Thanks for the suggestion though.

Thanks for suggesting I look at PGF, with lossless compression option as an option for archival preservation. It looks like this is what I should be using for image work.

*** jdd and Giles -

Your comments lead me to think I should keep camera-original JPG files as such, but convert to lossless PGF for processing. For archiving any processed images, should I also use lossless PGF files, because of the metadata preservation? I am assuming so until I hear otherwise.

SUMMARY --

My current revised archival storage plan is therefore -

CRW originals: store as such until 1.7.0 is readily available (no problem), then convert to DNG if file size is tolerable. Otherwise, convert to lossless PGF (which, I'm currently assuming, would be smaller).

JPG originals: store as such, period.

All originals: convert to lossless PGF for software processing, then JPG for web use, retaining PGF for archival storage of processed image, if desired.

As a reasonably informed, time-poor, amateur image photographer, I'm just trying to arrive at some simple rules for better handling my images. Digikam has so far been a real help to me, and the manual is a remarkable compendium of information and ideas. I especially appreciate the workflow procedures. People like me really NEED to be told what to do, as we have not the time to do a lot of thinking on our own.

Any and all comments are most welcome. Thanks for all the help!

Tom C.

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[pshute]

Tom said: "All originals: convert to lossless PGF for software processing, then JPG for web use, retaining PGF for archival storage of processed image, if desired."



Shouldn't you be retaining the original jpg file, and creating a pgf file for each edited version you create? And that should only be necessary if you need to reopen edited files for further editing. Simple edits, like a crop, might only need a jpg copy, but perhaps that's just complicating things.



These steps wouldn't be necessary if digiKam had non destructive editing, like Lightroom. Are there any plans for such a feature?



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On 01/24/2011 11:46 AM, Peter Shute wrote:
> Tom said: "All originals: convert to lossless PGF for software processing, then JPG for web use, retaining PGF for archival storage of processed image, if desired."
>
> Shouldn't you be retaining the original jpg file, and creating a pgf file for each edited version you create? And that should only be necessary if you need to reopen edited files for further editing. Simple edits, like a crop, might only need a jpg copy, but perhaps that's just complicating things.
I completely agree. My sentence was poorly written. It should have read
"For image processing, create lossless PGF copy...retaining original
and, if desired, processed PGF, in archive."  Sorry for the confusion!

t.
> These steps wouldn't be necessary if digiKam had non destructive editing, like Lightroom. Are there any plans for such a feature?
>
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--

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

"Sow a thought and you reap an action; sow an act and you reap
a habit; sow a habit and you reap a character; sow a character
and you reap a destiny." ~ Ralph Waldo Emerson (1803 - 1882)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tom Cloyd, MS MA
Private practice Psychotherapist
St. George, Utah, U.S.A: [phone]
<<  [hidden email]>>  (email)
<<  TomCloyd.com>>  (website)
<<  sleightmind.wordpress.com>>  (mental health issues weblog)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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[Elle Stone]

Hi, Tom,

Convert if you want, but don't throw away your crw files.Dng (like
digiKam!) is still in a state of flux and getting better and better.
What if the conversion to dng that you can do next year is better than
the conversion to dng that you can do today?

Check out this forum posting: http://forums.adobe.com/thread/528900?tstart=0

Or read the very bottom of this post
http://forums.dpreview.com/forums/read.asp?forum=1036&message=32904790

Dng is not magic. It has to decode proprietary information to do the
conversion, one raw file format at a time - there is always room for
improvement.

Converting to dng doesn't magically make your crw file open source or
completely known. It just means that a raw processing software that
doesn't support crw files might stand a chance of working if you
convert to dng first.

Also, at present there seems to be a bug in the digiKam dng conversion
- you might not be able to get your raw file out if you choose to
embed it. http://digikam.1695700.n4.nabble.com/Extract-cr2-from-dng-images-td3171026.html

About jpeg to dng - it really can be done - read this post:
http://www.barrypearson.co.uk/articles/dng/linear.htm

About "convert to lossless PGF for software processing", what software
were you going to use to process the image after conversion to pgf? I
just did a trial conversion of a jpeg to pgf with digikam. showfoto
can open it (didn't try processing), but gimp, cinepaint, and geeqie
couldn't open the pgf file.

Elle Stone
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[Gilles Caulier-4]

2011/1/24 Peter Shute <[hidden email]>:
> Tom said: "All originals: convert to lossless PGF for software processing, then JPG for web use, retaining PGF for archival storage of processed image, if desired."
>
> Shouldn't you be retaining the original jpg file, and creating a pgf file for each edited version you create? And that should only be necessary if you need to reopen edited files for further editing. Simple edits, like a crop, might only need a jpg copy, but perhaps that's just complicating things.
>
> These steps wouldn't be necessary if digiKam had non destructive editing, like Lightroom. Are there any plans for such a feature?

Already implemented in 2.0.0 !

Gilles Caulier
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[Remco Viëtor]

on Monday 24 January 2011, Tom Cloyd wrote:
(...)
>
> My current revised archival storage plan is therefore -
>
> CRW originals: store as such until 1.7.0 is readily available (no
> problem), then convert to DNG if file size is tolerable. Otherwise,
> convert to lossless PGF (which, I'm currently assuming, would be smaller).

I think you are missing an important difference between CRW/DNG and PGF/JPG
here: CRW, DNG and other raw formats store the information as captured by your
camera. To store an image as PGF or JPG, there are a few processing steps,
that can be done in different ways (too long to discuss here, see for instance
http://www.cambridgeincolour.com/tutorials/RAW-file-format.htm).

Short answer: keep your raw files (CRW or other), or perhaps convert to DNG.
DO NOT store them only as PGF or (worse) JPG.

And wrt. size: PGF or PNG will be BIGGER than your raw files in most cases:
raw files store 12 or 14 bits/pixel, PGF/PNG will store 24 or 48 bits/pixel.

> JPG originals: store as such, period.
agreed, not much else you can do.
Also, avoid repeated edit-> store cycles with JPG, if you have to edit them,
store the edited copy as PNG or PGF, to avoid cumulative quality loss.

>
> All originals: convert to lossless PGF for software processing, then JPG
> for web use, retaining PGF for archival storage of processed image, if
> desired.

See above about RAW/DNG. When I process a raw file, I usually store the result
in PNG format (another lossless format, more commonly understood than PGF).
Then, if I need an image for display, or printing, I convert to JPG.

> (...)

Hope this helps to clarify a few points

Remco

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[pshute]

Amazing! Does it let you backtrack to a previous editing step?



How about versioning? And if so, does it just keep track of various stages of editing, or can you have different final versions of the same photo?







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----- Original Message -----

From: Gilles Caulier <[hidden email]>

To: digiKam - Home Manage your photographs as a professional with the power of open source <[hidden email]>

Sent: Tue Jan 25 07:22:25 2011
Subject: [Digikam-users] Re: need advice re: format conversion



2011/1/24 Peter Shute <[hidden email]>:

> Tom said: "All originals: convert to lossless PGF for software processing, then JPG for web use, retaining PGF for archival storage of processed image, if desired."

>

> Shouldn't you be retaining the original jpg file, and creating a pgf file for each edited version you create? And that should only be necessary if you need to reopen edited files for further editing. Simple edits, like a crop, might only need a jpg copy, but perhaps that's just complicating things.

>

> These steps wouldn't be necessary if digiKam had non destructive editing, like Lightroom. Are there any plans for such a feature?



Already implemented in 2.0.0 !



Gilles Caulier

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[Elle Stone]

Gilles, I think you said above that PGF stores metadata. Yet when I
used the digikam image editor to open a jpeg with lots of embedded
metadata and immediately save it as a PGF file (no editing done), and
use exiftool to look at the metadata, none of the important metadata
was written to the PGF file. Instead there were several lines of new
metadata regarding "MPEG" with information such as AudioLayer : 1
AudioBitrate : 48 kbps SampleRate : 8000
which as my little jpeg isn't an audio file, is confusing - this
metadata is totally made up out of thin air.

When I open the same jpeg with the digiKam image editor, but save as
tiff or png instead of pgf, all the jpeg original metadata is written
to the tiff and the png. Is the problem that I'm still stuck on
livexiv2-v0.19?

Tom, you asked, "what converted format would YOU use - PGF for Digikam
and PNG for Gimp, or PNG for both, or something else?" I keep my raw
(cr2) files as cr2 files and will continue to do so even if I
eventually decide to also use dng. I keep my camera-generated jpegs as
jpegs, just as they come from the camera.

When I use Gimp to process a camera jpeg file, I immediately save the
file as "file.xcf" (Gimp's native format). General advice, as others
have suggested: never process a camera jpeg original - always work
with a copy, and immediately save that copy in a lossless format
before further processing. If I want to work further with a file
outside of Gimp, I export as tiff (call me old school), but I'm
looking into using png because there are a lot of software
compatibility issues with tiff. If I'm done processing, I export as
jpeg or png for the web. Regarding PGF and digiKam, I'd use png
instead.

A little experiment:
Original jpeg: 37 KB (its an extracted preview, not a camera-generated jpeg)
Some file size comparisons, all files saved with digikam starting with
the original jpeg
Saved as lossless PGF: 265 KB (7 times bigger)
Saved as png highest quality: 251 KB
Saved as tif: 943 KB
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[Gilles Caulier-4]

2011/1/25 Elle Stone <[hidden email]>:
> Gilles, I think you said above that PGF stores metadata. Yet when I
> used the digikam image editor to open a jpeg with lots of embedded
> metadata and immediately save it as a PGF file (no editing done), and
> use exiftool to look at the metadata, none of the important metadata
> was written to the PGF file. Instead there were several lines of new
> metadata regarding "MPEG" with information such as AudioLayer : 1
> AudioBitrate : 48 kbps SampleRate : 8000
> which as my little jpeg isn't an audio file, is confusing - this
> metadata is totally made up out of thin air.

Exiftool do not support PGF format. report this problem to Exiftool team

Exiv2 0.21 support this format. I'm sure, i implmented it myself...

http://dev.exiv2.org/projects/exiv2/repository/entry/tags/0.21/src/pgfimage.cpp

>
> When I open the same jpeg with the digiKam image editor, but save as
> tiff or png instead of pgf, all the jpeg original metadata is written
> to the tiff and the png. Is the problem that I'm still stuck on
> livexiv2-v0.19?

As i said, update to Exiv2 0.21

>
> Tom, you asked, "what converted format would YOU use - PGF for Digikam
> and PNG for Gimp, or PNG for both, or something else?" I keep my raw
> (cr2) files as cr2 files and will continue to do so even if I
> eventually decide to also use dng. I keep my camera-generated jpegs as
> jpegs, just as they come from the camera.
>
> When I use Gimp to process a camera jpeg file, I immediately save the
> file as "file.xcf" (Gimp's native format). General advice, as others
> have suggested: never process a camera jpeg original - always work
> with a copy, and immediately save that copy in a lossless format
> before further processing. If I want to work further with a file
> outside of Gimp, I export as tiff (call me old school), but I'm
> looking into using png because there are a lot of software
> compatibility issues with tiff. If I'm done processing, I export as
> jpeg or png for the web. Regarding PGF and digiKam, I'd use png
> instead.
>
> A little experiment:
> Original jpeg: 37 KB (its an extracted preview, not a camera-generated jpeg)
> Some file size comparisons, all files saved with digikam starting with
> the original jpeg
> Saved as lossless PGF: 265 KB (7 times bigger)
> Saved as png highest quality: 251 KB
> Saved as tif: 943 KB

JPEG is lossy format. You cannot compare to lossless format as well.

It's strange than PNG and PGF size are similar. In general PGF is
sivized by 2 compared to PNG.

I'm sure that for tiff, you have not used deflate compression option.
In this case TIFF size = PNG size.

If you want to compare PGF and JPEG, turn on lossless mode in PGF and
compress data. Compare after that image quality against JPEG.

For the same image quality, PGF file size is in general 2 or 3 time
better than JPEG file size (something similar than JPEG2000)

Gilles Caulier
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[Elle Stone]

Gilles, I sent a couple of sample pgf files to ExifTool's Phil Harvey, per his request. But even though pgf is not yet on the list of exiftool officially supported file types, it seems the real problem was just that I had exiv2 0.19. Now that I have exiv2 0.21 and libkexiv 1.2.0, exiftool is reading the pgf file metadata just fine.

Elle Stone

[Elle Stone]

Oops, sorry, it wasn't really a pgf  - somehow I saved a jpeg as a pgf
but it wasn't really.

On 1/25/11, Elle Stone <[hidden email]> wrote:

>
> Gilles, I sent a couple of sample pgf files to ExifTool's Phil Harvey, per
> his request. But even though pgf is not yet on the list of exiftool
> officially supported file types, it seems the real problem was just that I
> had exiv2 0.19. Now that I have exiv2 0.21 and libkexiv 1.2.0, exiftool is
> reading the pgf file metadata just fine.
>
> Elle Stone
> --
> View this message in context:
> http://digikam.1695700.n4.nabble.com/need-advice-re-format-conversion-tp3222538p3237201.html
> Sent from the digikam-users mailing list archive at Nabble.com.
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[gerlos]

Il giorno 25/gen/2011, alle ore 14.28, Elle Stone ha scritto:
> A little experiment:
> Original jpeg: 37 KB (its an extracted preview, not a camera-generated jpeg)
> Some file size comparisons, all files saved with digikam starting with
> the original jpeg
> Saved as lossless PGF: 265 KB (7 times bigger)
> Saved as png highest quality: 251 KB
> Saved as tif: 943 KB

Maybe your experiment is not realistic, I suppose because the start image was too small.

Here's my results on a 18 Mpx JPG image, generated by my Canon SLR at maximum quality ("L"):
IMG_5565.JPG:  5,9M (original image)
IMG_5565.tif:     51M  (uncompressed data)
IMG_5565.jp2:  15M  (Jpeg-2000, a little more than twice the size)
IMG_5565.pgf:  16M  (a little more than Jpeg-2000)
IMG_5565.png: 18M  (PNG slightly bigger than previous one, and 3 times bigger than original)
IMG_5565.tif:     18M  (compressed TIFF, same as PNG)

When converting the same image to 16 bits:
IMG_5565.tif:   102M  (uncompressed data)
IMG_5565.pgf:   68M  (a little more than Jpeg-2000)
IMG_5565.png:  82M  (PNG slightly bigger than previous one, and 3 times bigger than original)

It seems that size advantages of lossless PGF over PNG are more relevant with bigger files.
Hope these figures are useful.

regards
gerlos

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