Out of the box GIMP can handle a huge number of file formats, however it does not handle Raw files directly. You can use DPP or whatever to do your raw conversion save a file (jpeg or tiff) and then edit with GIMP, or alternatively you can install the UFRaw plugin and standalone application.
Some things are best done at the Raw stage, such as Exposure tweaks and white balance adjustments, others are just useful at this stage such as level/curves/saturation adjustments. And even Black and white conversion can be done here.
UFRaw is open source software just like GIMP, it is not an image manager, or a fully fledged editor, it is intended to open a raw file, tweak it, and pass it in an understandable form to GIMP. It will not replace your existing RAW editor, but it should happily co-exist with it. I'm quite happy with DPP but sometimes I go to UFRaw as it can be more powerful to work with. UFRaw does all its manipulations in 16-bit.
You can get UFRaw for windows from here >> http://sourceforge.net …=127649&sel_platform=3514
UFRaw does not let you view greater than 50%, and it also does not have any kind of sharpening, remember its job is to get your image into GIMP so you can do that kind of thing in detail. It works on a global level. The first image I've attached is of a badly underexposed shot opened in UFRaw.
How to do things. Below is a quick guide, if you want more details you can use the ufraw site http://ufraw.sourceforge.net/Guide.html
Exposure Correction
1. Use the slider to add positive or negative exposure bias
2. The top histogram is of the RAW and the conversion curves, the bottom histogram is of the actual output of the conversion.
3. You can put absolute values in the box beside the slider. If your used to clicking with DPP and going between 0.17 and 0.33, it will do the same, but allow you to put in any value. If you want 0.34 you can have it.
4. The slider allows you to go up or down 3 full stops (dpp only does 2 stops)
5. The histogram at the bottom updates live, it also shows below it absolute values for the percentage of over/under exposed pixels. You can hold down the mouse on either of the indicate buttons to preview blown pixels. You can click the checkbox next to the indicate buttons to leave these warnings on.
6. For my image, it is showing me that 0.2% of the blue channel is underexposed, when I click indicate it showed the centre of each of the flowers was underexposed. Also the histogram looks to be nearly a full stop from the right side. I pushed up exposure to 0.90, which indicated 0.0% for all channels. The indicator still showed some pixels underexposed, but as it was less that 0.0% this was good enough for me.
Extra credit
The 4 buttons next to the slider are
1. Highlight restoration mode (3 modes)
2. positive exposure correction (Digital type, film type)
*Digital* emulates the linear response of the digital sensor. This is mathematically correct, but can result in harsh cutoffs.
*Film* adds a "shoulder" to the response curve, emulating the soft behavior of film. IMHO a great feature
3. Auto Adjust Exposure
4. Reset Exposure to default.
White Balance
1. This is a drop down pick whatever suits the shot. "Camera WB" means use the white balance as the camera recorded it. "Auto WB" means UFRaw should figure it out by itself. All the other standard options are available (daylight, cloudy, etc)
2. Once you pick a white balance, you will see the Temperature and Green value displayed below as well as channel multipliers. You are free to tweak these to get the exact balance you want.
3. You can also pick a white point straight of the image. UFRaw does this slightly differently. Most apps you click the dropper, than click on the white point. With UFRaw you draw a box of any size around a sample area of the photo, then click the dropper and it will white balance based on that area instead of just a single pixel point. This seems odd but can work quite well if you find yourself clicking all over the place with the dropper in DPP and never quite getting it right.
4. White balance will also affect the histogram, so make sure you don't blow a channel by changing it.
You can also denoise, and do dark frames on this tab, but you will have to play around with those yourself and with the tutorial on the UFRaw site.
Next tab is the Grayscale tab, simple gives you 4 different ways of converting to Black and White. This will be covered further in a later topic. Next tab is a global curve, you can apparently load nikon tone curves here and things like the Fotogenetic Wedding curve V3.5. I usually just adjust the black point and add a slight curve if needed.
Colour Management is the next tab.
This is a vastly complex topic and I don't want to go there yet, but you can load an input profile, output profile and display profile. For my Images input profile "No Profile" is fine for sRGB images. If you shot the image in AdobeRGB you can click folder and point it at C:\Program Files\Canon\Digital Photo Profesional\icc\AdobeRGB.icc. For the output sRGB 8bit works perfectly for GIMP, if you intent to output to anything else again you can load any icc profile you like. For display profile, this is your monitor profile, or System default if you don't have one.
Saturation is the next tab.
You can slide up to make it more saturate, or slide it down to go all the way to greyscale. You also can apply a separate saturation curve here, again keep an eye on that histogram.
Next Tab is Crop, ignore this do it later in the GIMP. Next Tab lets you save a file, but as we are going to GIMP so we don't need to bother. The last tab shows you some basic EXIF info about exposure and lens. A lot more is available but only a few fields are shown, but don't worry all of it is passed to the GIMP.
When you are happy with the RAW, click the GIMP button at the bottom right (picture of the dog on it). GIMP will now open with your raw converted to GIMPs internal format. At this stage you should probably save a .XCF before you start your editing.
Attachment 1 is a screenshot of UFRaw before working on an image
Attachment 2 is a screenshot of GIMP with the file UFRaw handed to it.
The next tutorial on Cropping in the GIMP is here >> https://photography-on-the.net/forum/showthread.php?t=680024
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please help me out before my time is done on the computer and i go to sleep mad and frustrated lol .
