DXO demosaicing artifacts

Started Jun 4, 2019 | Discussions thread
sankos Senior Member • Posts: 2,378
Re: DXO demosaicing artifacts

IanYorke wrote:

sankos wrote:

).

I agree with the OP that DxO could improve their demosaicing -- I have come across images where moire and mazing created some problems such as e.g. the watercolour effect. Whether this matters depends on the camera-lens-output type combination so many people might not realize this because they don't pixel-peep or their hi-rez monitors do a good job of hiding the problems from them.

How does a high resolution monitor hide the problems. I have always thought high resolution was an advantage?

Ian

Good question. It does offer an advantage in the sense that you don't see individual pixels at 100% view (which is what you want for normal viewing purposes). But when evaluating demosaicing you actually want to see individual pixels so you need to view the image at higher magnifications when using 4K and up, and many people don't realize that. I can see this problem when e.g. people discuss the watercolour effect and worms at the Fuji DPR forum (a notorious subject over there) -- some people talk about how Adobe demosaicing for Fuji X-Trans cameras has no problems because they can't see it on their super fancy new monitors but the problem is if you want to discuss demosaicing you need to pixel peep.

Here's a demosaicing test I ran recently on a Sony a6400 file. The DPR Studio Scene has a couple of good sections for such a test, my favourite is the drawing:

DxO PhotoLab2 demosaicing

Here you should be able to see moire and mazing problems with the DxO demosaicing. I have to look at 200% magnification to really see the difference between various raw converters and my monitor is an oldish HD Eizo, so people with 4K monitors are advised to look at the file at even higher magnifications.

I ran the raw file through various raw converters and my subjective preference is the demosaicing used by C1 and darktable/RawTherapee (AMaZE). DxO and Lr are somewhere in the middle of the pack (somewhat similar artefacting to a sharpened version of the VNG algorithm), the worst demosaicing was used by Sony's Imaging Edge raw converter and ON1 (the latter is pretty similar to Lr demosaicing only it is aggressively sharpened but has no coloured moire). Here's C1:

Capture One 12 demosaicing

and here's darktable when using AMaZE with some colour smoothing to fight colour moire:

darktable 2.6.2 AMaZE demosaicing

Although C1 and dt have some problems with moire, yet I like the quality of the highest frequency detail, and they yield best results when you apply input sharpening to the file (these are all not sharpened as far as possible to set in each raw converter).

It's instructive to look at the scene rendered by some full-frame and medium format cameras to see the real detail in that drawing (as rendered by ACR).

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