dcraw problems with Panasonic Lumix DMC-LX3 in low light?

I have a Panasonic Lumix DMC-LX3 as a general purpose camera and am very
pleased with it. The camera has settings such that it will either create
a .jpg on the fly *or* create a .jpg *and* save a "raw" .rw2 file as well.

As I use Unix-ish systems, I have never played with the Windows software
that came with the camera, but the free open-source prgram "dcraw" is
able to read the .rw2 files and write them as .ppm files which I can then
make into .jpgs myself with cjpeg.

Anyway. With standard daylight shots, I am usually more pleased with
the jpgs I get from the "dcraw" process than those the camera creates itself.
It's not dramatic, but they are just slightly more pleasing to my eye.

However, I have recently taken two sets of photos at night with a tripod
and several second exposures. In theses cases, the jpgs produced by the
camera are quite a bit better than what I get from the raw files. I've
tried a number of different settings to dcraw (-W turned out to be quite
important, but still doesn't do the whole trick) but still haven't produced
anything as good as the camera jpgs and I'm curious if I'm missing something.

Here are three files from a recent night time trip to a local sculpture
garden's Christmas light program:

http://www.tednolan.net/misc/lumix/p1080248-camera.jpg
http://www.tednolan.net/misc/lumix/p1080248-dcraw.jpg
http://www.tednolan.net/misc/lumix/p1080248.rw2

The first is the JPEG produced by the camera itself.

The second is the JPEG I made with dcraw -W & cjpeg -q 95

The third is the raw file itself.

If you look at the pedestal and feet of the statue, the foot is clearly better
defined in the camera jpg. Also if you look at the color and highlights on
the statue's legs, those are clearly better in the camera jpeg as well.

Any thoughts as how to replicate the look of the camera jpeg from the raw
file with dcraw?

Ted

 

Try applying an unsharp mask to the dcraw shot.
You might also try to apply some noise supressing software, I
believe the camera uses such for the JPEG.

-Wolfgang

 

Thanks, I'll give it a try.

Ted

 

Which has almost certainly had an element of sharpening or unsharp mask
applied in the camera. You can probably find some control of sharpness
in the darker recesses of the menu system if you look hard enough.

Softness show up strongly on high contrast sharp edges. The image is a
bit odd in that it has been stripped with no embedded information or
thumbnails. But it has a custom quantisation table that suggests it is
ex-camera. The q-table is roughly equivalent to IJG q=98 by the way.

So you lost a bit of detail and had a smaller file size below for that
reason too. But most of the difference is due to the fact that the image
has a significant linear dependency between adjacent pixels.

Apply a small amount of unsharp masking to get the edges to your liking.
Overdo it and the edges will ring, but the right amount will give the
result you are looking for. 3 pixel, 60% is a starting point.

Camera makers know that sharpness sells so most P&S are rigged for
slightly overcooked sharpening by default.

Regards,
Martin Brown

 

Rather a round-about way to get there. Try ufraw. It uses the same dcraw
conversion engine and allows you to do simple editing - change the white
balance, exposure, etc. and output a jpg.

Excellent case for ufraw - you can adjust exposures, etc. on the fly, see
what it does, undo, try another, adjust a little more, whatever. It
should make your editing much better.

I've tried to look at your raw file in ufraw and it does not handle it
properly, but then I probably don't have the latest version (Debian
stable). You may be able to build it with your version of dcraw which
handles that format.

Since I was not able to check, I can't verify, but there is a good chance
you're losing some of the detail in the jpeg conversion. With ufraw, if
you get it to go, you can do your changes on the full data rather than
trying to pull info back out of the jpeg.

 

As mentioned, I could not get my version of ufraw to directly read your
file. But I was able to use the Adobe DNG converter under WINE to convert
to a DNG which ufraw could handle.

 

I'm sure it is. What part of 'stable' is it you don't understand?

 

I don't need it for what I normally do. I did this only to show the OP it
could be done in a variety of ways.

 

I'll take a look at it though I have shell scripts to do all the work,
so it's not really round-about for me.


Ted

 

I will definitely investigate ufraw!

Ted

 

Yeah, come to think of it, that image has been roatated from landscape
to portrait with jpegtran which doesn't lose any image detail (ie, it does
not decode and recode the jpg) but which does lose EXIF info.

 

If you are doing that you may as well let it optimise the Huffman
coefficients in the lossless encoder step to get a smaller file.

Few cameras do it because it takes two passes over the coefficient data
and is slower, but on a PC the time difference would not be noticeable.

Regards,
Martin Brown