This is part 2 of a comparison between Raw Therapee (RT) and Adobe Camera Raw (ACR) although I’m not sure how much I will be able to call it a “comparison” by the time I’m done.

The image I used in the first part of this post was a seascape taken at night under moonlight. The tones were relatively even, the detail in the rocks was subtle, and there were no extremes of lighting and contrast to deal with. Nearly all of those things exist in the city so for this post I’m using an image from Amsterdam taken in March at around 4:30 in the morning while I was suffering from extreme jet lag and couldn’t sleep.

I mentioned that RT offers the choice between three different demosaicing algorithms. I converted the image in the prior post using HPHD and was happy with the results.

I had originally planned to show some of the shortcomings of HPHD in this new image but after zooming in and out, in and out, in and out, for way too long I think that unless you’re viewing the image at 200%+ the artifacts HPHD produces are not visible and there is no chance they would show up in a print. But for what it’s worth I’ll will post some of the nitty gritty details anyway - I think it’s interesting to see the differences even if they’re largely irrelevant in most cases.

So first here are some crops from the sky showing the two RT algorithms and ACR - all with an additional curves layer to enhance contrast.

The 100% crops show minimal differences between the RT algorithms but the noise reduction applied by ACR is obvious. At 300% the difference between the RT algorithms in a smooth area are visible. EAHD produces a cross hatch pattern while HPHD seems to be more natual looking and does not show the pattern. I suspect this difference would be more exaggerated in an image with more noise to start with. This difference seems to be similar to the crops shown in this thread between the DCRAW AHD algorithm and the PerfectRaw AFD algorithm which looks very promising.

If there were zero noise reduction in the ACR crop it would look similar to HPHD.

Here are crops of some of the areas that HPHD produced artifacts:

Like I said this is really picky and although they’re not visible at 100% they are there in the HPHD conversion and not in the others.

Here are crops of all three at 100% and they are very similar - there is perhaps slightly more visible detail in the bricks and ornamentation in the RT crops but also more noise.

After I posted a link to part 1 of this post on the Luminous Landscape I got some not totally unexpected feedback from a supporter of one of the products suggesting that it was a flawed comparison because I wasn’t comparing “the best” output from each tool (including sharpening, noise reduction, etc) and therefore the results had no relevance to the real world of processing images. I suggested that in many cases, “the best” (either in overall image quality or what most closely matches what I want from the image) isn’t something that I generally get either entirely in the RAW converter without additional processing nor is it normally the result of a single RAW conversion. Secondly if you’re only applying capture level sharpening to the image in the RAW converter isn’t it even more important to be able to turn off default noise reduction if necessary to retain all potential detail in the image prior to beginning any post processing? In general, “the best” I could get out of either of the tools is probably far beyond what I would want to use going in to post processing.

In any case, before I post some crops of the image where I think I got “the best” from each application I want to mention a couple things that are important.

1. My computer had smoke coming out of it before I was done (er, gave up) so if you’re going to even attempt to compare two applications each with the potential for hundreds of possible output variations (taking in to consideration the variety of noise reduction and sharpening algorithms, etc) be prepared. Also be prepared that according to someone out there you will have done it completely wrong.

2. The Richardson-Lucy Deconvolution sharpening option in RT is a nice addition because it behaves differently than either the USM sharpening in RT or the sharpening in ACR. I was able to get more detail out of the window ornamentation, the bricks in the wall, the building ornamentation, etc, than I was using the USM option in RT or the ACR sharpening. I believe ‘Smart Sharpen’ in Photoshop uses something similar but I was not able to match the results using Smart Sharpen in post processing (not saying it can’t be done only that I couldn’t do it). The RL sharpening fared best when I let it do it’s thing and then masked out the smooth areas afterwards in Photoshop.

So without further delay here is “the best” I was able to do with each of these converters. As usual, a gradient map has been applied on top to convert to black and white and for consistency with my other non-scientific tests. For both I used the same mask to mask out the sky from the sharpened result - neither tool provides enough control for “damping” or “masking” the application of sharpening so I chose to do that in Photoshop instead.

At 100% there are some clear differences and I think they are entirely attributable to the RL Deconvolution sharpening method available in RT. To me the details in the ornamentation and small areas where leaves/branches are visible look more natural and less like I tried to add sharpening to bring them out. In addition there is more detail in the bricks in the RT version.

Finally, despite all the work getting “the best” out of each converter, when you view the image at 50% or print size there is literally no difference at all

This entry was posted on Tuesday, November 11th, 2008 at 8:19 pm and is filed under Blog, Technique & Equipment. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.