Below are some details of images which I captured in Raw format and converted with different programs (ACDSee Pro 6, Canon Digital Photo Professional, Lightroom 5, Raw Therapee V4.0 with "amaze" algorithm). The goal was to identify differences in their demosaicking algorithms and quality.
In order to get comparable results I set sharpening to 0 or turned it off in all programs. I also turned off chromatic aberration correction to really reduce the image processing to a minimum.
The images were shot at an oldtimer show in Salzburg, Austria on a Canon 60D (no the newest model, but sufficient for this kind of test) with an EF-S 24mm F2.8 lens.
In all scenes you will find the ACDSee image in the upper left corner, the Canon DPP image in the upper right corner, the Lightroom image in the lower left corner and the Raw Therapee image in the lower right corner.
In this scene you can see how skewed lines are processed. The headlight of the car (a Jaguar) is in perfect focus. You can clearly see that ACDSee tends to create blocks of 2x2 pixels at lines at an angle of roughly 45° (staircasing). If you zoom in a bit you can even see some pixels which are obviously too dark (overshooting) at the upper left side of the headlight mount.
Raw Therapee shows some color artifacts all over the headlight. This crop is close to the center of the image, but still this could be due to chromatic aberration. Even though sharpening is turned off, the image looks unnaturally crisp.
DPP seems a little blurry but free of artifacts.
Lightroom has a good balance of sharpness and artifacts. If you look close enough you will find some color artifacts, but less than in the Raw Therapee image and also some blocky skewed lines, but not as bad as in the ACDSee image.
This scene shows a similar situation, only this time there is more contrast, which makes the artifacts visible even more. The crop is taken from the upper left third of the image, so chromatic aberration is noticeably stronger than in the crop before.
ACDSee can´t handle this situation at all. This image looks awful.
DPP smoothens out the CAs and creates a nice smooth image.
Again, Raw Therapee struggles with colors and Lightroom is somewhere in between. While artifacts (color and blocking) are visible, the image is sharper than canon´s.
This is a part of the image which is slightly out of focus. Sharpness is is not a big topic in this scene. Normally you would think that this makes demosaicking easier, but obviously this is incorrect.
Again, ACDSee fails in reproducing skewed lines. The creases in the man´s shirt show heavy staircasing and look awful.
Raw Therapee can handle this situation better, even better than Lightroom which also shows some light staircasing.
Canon DPP is the clear winner in this scene. The image is very smooth.
Similar situation than in the second image. Again, Canon and Adobe are the winners, ACDSee and Raw Therapee struggle with the high contrast skewed edges.
Another situation where ACDSee clearly fails. Skewed lines and edges are obviously not its strength. Raw Therapee can handle this situation much better, however, it shows color fringes again. Lightroom has some staircasing and color fringing as well. DPP has less sharpness but no artifacts at all.
This is a very interesting image. Red detail on black background is a difficult thing to handle for demosaicking algorithms because there is no information that can be extracted from the green channel which could support the interpolation of the red channel.
ACDSee fails in this test even worse then ever before. There are bright pixels in the red lines which look like a pearl necklace. This is due to overshooting in the interpolation of the missing pixel values.
In Raw therapee the two parallel lines can be clearly separated, but they look somewhat "digital". If you zoom in you can see that the red lines seem to be stitched together from pieces of 45° lines.
When you zoom in you will also identify some overshooting and pearl necklaces in the Lightroom image but by far not as bad as in the ACDSee image.
The DPP image does not separate the two parallel lines as good as the others, but again, it looks less processed and more natural.
In general it seems that Canon does not put so much detail into the image, but therefor the images are completely free of demosaicking artifacts. This means that the images look very natural and not digital, even when you zoom in. The other three programs produce very crisp images, even with sharpening turned off. This makes the pixes sturcture visible and creates a "digital look". Also it allowes interpolation artifacts to be more pronounced.
After having analysed these (and some more) test images, my rating is the following.
1) Canon Digital Photo Professional
2) Adobe Lightroom 5
3) Raw Therapee V4.0
4) ACDSee Pro 6
I have to emphasize once more that this rating is just about the quality of the demosaicking. It does not take into account other features of the tools. Also, obviously, the selection of the tools is by far not complete. The reason why I tested exactly these four is just because I have them. I bought ACDSee some time ago. When I figured out that it´s image quality sucks, I bought Lightroom. And well, Raw Therapee is for free and DPP came with the camera anyway.
If you like, please post your opinion and your own experiences.
