Workflow

I will not describe my complete workflow here, there are much better tutorials online or in books. Instead, I would like to demonstrate some features when using UFRaw and Gimp, that are maybe not so obvious.

Camera Profile

After switching to the D300s, suddenly my images were way to dark in UFRaw:

I soon realized, that I needed the correct profile for my camera. With that in place, the same image resembles much more what I saw when I took the picture:

Profiles for several cameras can be found on the UFRaw website. If your Nikon is not included, this blog article explains how to generate the profile using Nikon's free ViewNX software.

White Balance

When doing wildlife photography, you have to cope with different lighting conditions. When shooting, I don't care for the white balance of the images, the camera is set to "automatic". Instead, nearly all images have to be color corrected later - which is no problem in a RAW workflow.

The presets found in UFRaw are a very good starting point for selecting the correct white balance. In fact, most of the time I only need "sunshine" or "cloudy", very seldom "shadows". From time to time I like to adjust the color temperature a little, but most of the time the presets get it right.

Noise Reduction and Sharpening

In wildlife photography you often need short shutter speeds. Given a certain amount of light, you can either use a large aperture (and a big lens), or you have to increase the sensitivity of the sensor, which means increasing the ISO value. The cost you have to pay is noise.

This image of a Kestrel was accidentally taken with 800 ISO (I could have used a much smaller value), and the actually blue sky appears grainy:

To cope with this problem, most image processing software offers some sort of "denoise" function. There are even dedicated programs like Noise Ninja or Neat Image. UFRaw has its own noise-reduction mechanism (called "Interpolation" in the GUI), and it is much better than I first anticipated.

Another aspect of RAW image processing is: Images need to be sharpened manually. When shooting JPEGs, the camera does this automatically, but when shooting RAW, this step is missing. So if you think your RAW images look blurry and smudgy, one reason might be that you forgot this step. UFRaw provides no mechanism for sharpening the images, but you can do this in Gimp. The wavelet sharpen plugin is the correct tool for this step.

The trick is now to find a good balance between noise reduction and sharpening. If you sharpen a noisy image, the noise gets enhanced:

If you reduce too much noise, the image becomes even more blurry, and the sharpening process will have a hard time compensating this:

If you adjust both values carefully, you can get an acceptable result:

To see the combined effect of both processing steps, the next page allows you to manipulate both values and compare two different settings.