Colour Cast from F-Spot to UFRaw

I use F-Spot tp preview images and the ones I want to do something with I right click and open in Gimp which uses the UFRaw plugin to read the raw file. I have never had this happen before but with my first attempt at star photos the following has happened:

This is how the photo appears in F-spot (and on the cameras screen):

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO

Nobody has any thoughts on this? I've wanted to share some photos but until I can get Gimp/UFRaw to play nice I can't.

I don't use Gimp or F-spot, so can't comment directly. Maybe a photo with more light and subject matter would help us see what you are seeing. How does the final jpeg conversion look? Maybe post another set of screen shots of another image and then the final jpeg out of Gimp and we could see more?

ions wrote in post #9300242
Nobody has any thoughts on this? I've wanted to share some photos but until I can get Gimp/UFRaw to play nice I can't.

Are you looking at the jpeg preview of your RAW file when you open it in f-spot? That could explain the difference.

From the screen grab of UFRaw you posted, the White Balance is set to Manual. Try to set it to "Camera". That'd be my best bet.

As far as I can tell I am not looking at a jpeg preview in F-spot, and only shoot raw so I know it's not a jpeg file I'm looking at. Maybe I am? How do I know for sure? But even if I am what is in Fspot matches the camera's display which is what I want. In UFRaw no matter what I set it to - Manual WB, Camera, or Auto it's still not showing the image as F-Spot or the camera does. All 3 are underexposed considerably compared to what the camera and F-spot display.

I tried a few examples of snow shots but other than a mild darkening there isn't a change in colour cast, although the darkening does bother me it is quite slight; certainly not as severe as what is happening with the star shots. Here's another example with star shots that may better show what's going on:

F-spot:

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO

I don't use F-Spot (I use GQview) to preview, but I do use UFRaw.

There is a 1/4 res. jpeg embedded in my 40D's RAW files that GQView can read. You should be able to tell if you are looking at the jpeg or the raw by the resolution of the image. Have FSpot go 1:1 and see how "zoomed" it appears.

As for UFRaw, make sure you haven't set the different curves, linearity or gamma setting to something strange. What I did, was open a cr2 with UFRaw directly (NOT as a GIMP plugin). You'll get an extra tab that will allow you to save a current settings for UFRaw "just this once". Set all the sliders to some sane default value and then exit UFRaw. Then each time you fire up UFRaw (as an app or a plugin) it will always start with those sane values.

Hope this helps. If not, just say so and I'll post a more in depth explanation.

I can confirm that Fspot does use the embedded jpeg in the raw as the preview.

I'd go through all the settings in UFRaw first setting them back to default. Maybe you missed something you changed on the last picture you did to cause this. Sometimes it's memory of settings can be a curse as well as a blessing.

I must have changed settings in UFRaw at some point. Going to look into getting them back to default.

Just noticed that F-Spot is indeed using jpeg... note the cursor pointing that out:

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO

For me to get close to what the jpeg looks like:
1. Set white balance to "camera"
2. Gamma .45
3. Linearity .02
I use the "color matrix" camera icc since I can't find a 40D specific one.

That gets me really close to the jpeg on my 40D. I think the camera is also doing a bit of contrast enhancement and sharpening on the jpeg. I wouldn't be shocked if it is also boosting the saturation.

Of course this is just a starting point and assumes the camera got the white balance right and that UFRaw can read the camera's white balance value correctly.

This experience is making me recall this thread. So the camera has recorded an image in raw but on the screen "lies" to me about the data it recorded which I then have to recreate by fiddling with raw processing to get it to look the way the camera told me it did. Really? I gotta be wrong here...

ions wrote in post #9304077
This experience is making me recall this thread. So the camera has recorded an image in raw but on the screen "lies" to me about the data it recorded which I then have to recreate by fiddling with raw processing to get it to look the way the camera told me it did. Really? I gotta be wrong here...

No, you're right. The Raw file includes a smaller JPEG preview of the photo, and the camera does some default processing on the jpeg, like sharpening, increase saturation, etc.

Also, don't trust your camera display too much, it's a tiny screen of low resolution that is not very accurate. Some camera models have better screen than others (the new 920k models are).

RAW files are just that: raw output. So you indeed need to do some post processing until you get a good result. Try the settings cms_censor proposed. Personally I also set the curve slightly towards the top left and boost saturation to 1.50. I like to picture bright, so I usually increase the exposure compensation too (on a shot by shot basis for this settings, sometimes I get the exposure right from the shot itself).

But yeah, bottom line is that you have to do a minimum of post processing on your RAW files. JPEGs are already post processed by the camera itself.

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ions wrote in post #9304077
This experience is making me recall this thread. So the camera has recorded an image in raw but on the screen "lies" to me about the data it recorded which I then have to recreate by fiddling with raw processing to get it to look the way the camera told me it did. Really? I gotta be wrong here...

Just to be clear here. The settings I recommended aren't "fiddling". They get UFRaw set to a baseline that closely matches my 40D hardware. (I could probably get closer with a Canon ICC profile for the camera since that color correction profile is being used in camera to generate the jpeg.) Once you pull a raw image up with those settings, anything you do to the sliders after that is the fiddling part.

As I see it, it boils down to this: Do you want these processing steps done for you in camera or do you want to be able to do these steps yourself and then tailor them to suit the specific image's needs? In a larger color space and without lossy compression from the get go.

I tried the suggested settings and they did improve the raw images but not to the level that the jpeg preview offers. I guess I have to fiddle until I find what the 7D settings would be. I guess I'm going to have to accept that some screen fiddling is a part of this. I will do so eventually but it will be reluctantly and with a pile of whining.

Thank you for the help guys!