Saturday, April 07, 2007

The effects of RAW converters on DSLR quality

Warning, links below lead to web pages with large graphic files.

The perceived quality of a digital camera, particularly DSLRs and their lenses, is heavily dependent on the tools you use to process the image. Not just the "recipe" or settings you use, but also the mathematical algorithms in the particular software package that you use.

Take the demosaicing algorithm. This is taking the red/green/blue camera sensor data and overlaying the colors into pixel data. Somewhat surprisingly, there are various ways this can be done, each with trade-offs for resolution, color, and artifacts. See this comparison.

Sharpening is another algorithm that varies from tool to tool. See this comparison.

Don't take those comparisons as a way to judge the absolute quality of any of the software, because the results are highly dependent on the content of the test image used. And there lies the rub. When you think about it too much, you realize there is an infinite solution space.

The variables are the camera, lens, subject, lighting, exposure, software, settings. A particular image might look best post-processed (PP) in Adobe Camera RAW with sharpening (and at least 6 other controls) set a particular way. Another image might look best processed in Silkypix.

So what to do? You can't run every picture you take through every software tool with every setting. I barely have time to run my best pictures through one tool!

You have to pick a RAW processing tool and learn how to use it well, learn what all the adjustments do and their combined effects, which adjustment to apply in which order. You have to develop different recipes for different types of images. And by recipe I don't mean a set of absolute settings, I mean the methodical steps you go through to adjust the image.

Portraits might be one recipe, landscapes another, low light interior another, and so on.

Do it wrong, and you are likely to blame the camera, or the lens, or the software you are using. Do it right, and you will have a very pleasing result. Maybe not the ultimate best result that could be accomplished some other way on some other software, but then you can't know every software package and you can't try every recipe.