in praise of RawTherapee, "Amaze" demosaicing algorithm

Started Jun 10, 2011 | Discussions thread
GaryW Veteran Member • Posts: 8,541
Re: point of the posts is demosaicing *differences*

RussellInCincinnati wrote:

Yes, now that you mention it, the top photo in my post yesterday of the magazine halftone is a bit "buzzy". I appreciate your hint Gary, and will experiment with a smaller sharpening radius. Hmm, that's a fragment of a 1 meter wide enlargement on my monitor, would it still be buzzy at any normal print/display size?.

Why bother with deconvolution or any sharpening then, if you're not going to zoom in on that level of detail? I'm just saying, if you're going for the best pixel-level resolution, don't overcook the sharpening and mess it up. And it might get a bit visible at a lower resolution/print... perhaps not as something very obvious, but just giving it an "off" look, but I can't say that I've tried to make the comparison.

Anyway, the overall point of interest in this thread is not to show a workflow that is "good" in any absolute sense.

That's fine, but I take opportunities to try to get people to think about sharpness, as most people overdo it, IMHO.

Rather it's to show the difference between AHD demosaicing in my quite typical Picture Window Pro program, versus Amaze demosaicing+RL Deconvolution in Raw Therapee.

But I think comparing workflows is fair. If you force yourself to add more sharpening where it is not needed, it's still not its best. Maybe utilize each technique to get its best out of it. I like to make comparisons of real-world, this-is-how-I-would-do-it over perfectly-and-arbitrarily-"fair". But as long as you are clear that you're just forcing an equality of procedure to prove a point, that's OK, but since deconvolution is just another kind of sharpening, I'm not sure you really have to run it through the separate sharpening technique. As I said, if you really think it needs touching up, I'd try a small radius. Often I find deconvolution to be sufficient.

Is there a difference in apparent sharpness, or fine detail, even though both programs' images were put through the same final unsharp masking? Apparently yes.

Maybe I should have just stuck with my original quite clear comparison a few weeks ago (that included RL Deconvolution for the Amaze images) and left it at that, even though that picture was not taken under well-controlled conditionn For some reason had mis-spelled AHD demosaicing as "ADR algorithm" in the picture labels:

Adopting RT Raw Therapee has been for me like getting a whole new set of lenses. And along with RT's 5-pass false color suppression routine, as shown above, it's solved maybe half of Nex moire problems. Without blurring anything.

I agree -- using RAW and taking that extra time is well worth it, at least for shots that matter.

I also like DxO for its noise handling. I find it superior to the free RAW converters. It has its own deconvolution, but only for certain lens/camera combinations, unfortunately.

By the way RL Deconvolution sharpening (am thinking of it as "pre-sharpening", since it does not sharpen so much as to screw up later resizing of an image) is faintly related to the technology involved in the new "lightfield camera", mentioned in another contemporaneous thread of this Sony Nex forum.

It can extract a bit of detail where you though there wouldn't be any more to get. You can definitely overcook deconvolution, though. It's not a cure-all.

On the other hand, normal sharpening is easily overcooked and messes up your low-level detail.

Put another way, let's say you like the image quality step-up from bothering to process raw images, rather than accepting Sony in-camera JPEGs. If so, then am suggesting/showing there's a similar jump up in quality to go from most raw file processors, without the newish AHD demosaicing, to Raw Therapee, with its Amaze demosaicing+RL Deconvolution.

If you don't mind spending 1 minute processing each raw file, on a dual core 2.1 gigahetz Intel box. RT does support multiple CPUs (e.g. dual or quad core) well.

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Gary W.

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