Variation in colour balance Shotwell/UFRaw/GIMP

[Michael Hendry]

Binary package hint: shotwell

Ubuntu Lucid Lynx 10.04 LTS

Shotwell 0.7.2

Working with NEF images from my Nikon D70 camera.

When I view an image in Shotwell and then opt to open it in UFRAW, I expect to see the unmodified image in UFRAW, but this is not the case, it appears "warmer" than the Shotwell view, and this warmer image is sent on to GIMP when I opt to do so.

However, if I opt to open the same Shotwell image in GIMP, it looks the same as it does in Shotwell.

Viewed in the file manager, the image appears "warm", as it does if I opt to open it in UFRAW. If I opt to open this image in GIMP from the file manager, it is opened first in UFRAW, and appears "warm", and is transferred as such to GIMP.

Looking at the system as a whole as a black box (lacking knowledge of what's going on inside) my conclusion is:

Shotwell takes a "cool" view of a NEF image, which it presents on screen, and will pass on to GIMP if requested to do so.

When Shotwell passes an image to UFRaw, UFRaw takes its own view of the image, and presents it "warmed up" in comparison to Shotwell's view, and passes this on to GIMP.

Direct use of UFRaw from the file manager, or invoking UFRaw via a request to open the file in GIMP results in the "warmer" image being opened.

It seems to me that it's Shotwell that's out of step with the rest of the world, but I don't understand how these programs interact with one another.

[Adam Dingle (adam-yorba)]

Michael,

your understanding of what's going on inside the black box is basically correct. When you import a RAW photo into Shotwell, Shotwell renders the image into a JPEG. If you then open it in GIMP from within Shotwell, Shotwell passes the JPEG to GIMP. If you open it in UFRaw from within Shotwell, then Shotwell hands the RAW image to UFRaw, which renders it itself. If you open it in GIMP from the file manager, GIMP uses UFRaw to render the image.

At the moment, Shotwell and UFRaw's renderings of the RAW image may look quite different. Of course, you're right that ideally all GNOME photo programs should develop RAW images in the same way. We'd like to improve the situation, and we have a Trac ticket about this at http://trac.yorba.org/ticket/2246 . This won't happen for 0.8, but I hope we can look at this for 0.9.

[Michael Hendry (hendry-michael)]

Thanks, Adam.

Accepting that there won't be universal agreement on how a RAW image should be rendered, would it not be better to pass the RAW image to GIMP when "Open with External Editor" is requested, rather than the JPEG generated by Shotwell, which has by this time thrown away information held in the RAW image?

I now appreciate that there are two distinct routes available from Shotwell (direct to GIMP, or via UFRAW with the option of chaining onwards to GIMP), but there is no indication to the user that the first of these is passing an already-processed image on.

[Adam Dingle (adam-yorba)]

Michael,

Shotwell has no built-in knowledge of either GIMP or UFRaw specifically. Shotwell knows only of

1. an external editor that can edit JPEGs ("External photo editor" in the preferences dialog). If you invoke this editor on a RAW image, Shotwell will instead pass it the transformed JPEG.

2. an external editor that can edit RAW images ("External RAW editor" in the preferences dialog)

If you want to pass RAW images to GIMP, simply set GIMP as your external RAW editor. Then when you open a photo using Shotwell's Open With RAW Editor command, Shotwell will invoke GIMP.

[Michael Hendry (hendry-michael)]

Thanks, Adam.

Now that I understand what's going on, I can ensure I make the RAW adjustments on the way to GIMP.

Having said that, I don't think it's Shotwell's place to be performing a file conversion when arranging for an image file to be edited by an external program. There's no mention of this in the Edit=>Preferences dialogue when an external program is selected, nor is there a mention of it in the manual, so it was a reasonable assumption on my part that the external program would be supplied with the original file to work on.

After all, GIMP knows what to do with a RAW image if it's opened from the File Manager, so why shouldn't it do the same when passed a RAW image by Shotwell?

You may think I'm just being awkward here, but if I hadn't realised there was something odd going on here, I might have been discarding underexposed images (for example) because I couldn't improve them sufficiently in GIMP.

[Sebastien Bacher (seb128)]

the bug should be fixed in the current version so closing it but feel free to reopen if you still get the issue with it