Digital Light & Color

Hi,

I'm puzzled by the fact that Olympus raw files (ORF) converted in PW (PW Pro 5.0.1.6) acquire an upleasant gray mesh which is quite distinctive at larger zooms. To show you what I mean, here are some examples. This is a test picture of gray autumn sky - it should be quite uniform.

Here is how it looks when the raw file is processed by PW (all images are zoomed 4:1):
Do you see the gray mesh? It's present all over the picture on every ORF file I process in PW regardless of camera settings or RAW dialog settings.

Here is the same raw file opened in Olympus Master software (again zoomed at 4:1): And yet another example - this time the raw file is processed by Raw Therapee (zoomed at 4:1):
In both latter cases the sky is quite uniform.

(I'll post one more example in the next post because of attachements limit in this forum)

I suspect PW has problems handling ORF files. I remember that in the previous version, when only AHD interpolation was used, it was simply impossible to process Olympus raw files in PW because of ugly artefacts introduced in the process. With the new version I am able to use VNG interpolation but still the outcome is not satisfying, as you can see.

Do you think the gray mesh could be corrected in some way? (It's strange that a freeware program, like Raw Therapee, has no such problems).

Regards,

Bogumil

And here's the last example I promised. This is in-camera generated jpeg (zoomed at 4:1): Regards,

Bogumil

The four samples that you show are not all of the same contrast -- the PW image has the greatest contrast which accentuates any artifacts. But that said, all interpolation techniques create artifacts of one kind or another. Generally tweaking the interpolation algorithm to reduce one artifact will increase some other artifact. So the best way to judge an interpolation technique is by its overall performance. Extreme blowups of a small selected areas tell you relatively little unless you compare many such areas chosen across the full spectrum of different image structure situations.

Remember too that PWP also offers VNG interpolation (though not for all cameras). If it is available you might want to give it a try. The setting is in the Options menu under Advanced Settings. You can also make it your default in raw settings.

Kiril

Kiril,

Thank you for your reply.
The PW image *was* generated with VNG interpolation so no improvement is possible by changing the interpolation method (AHD is much much worse).

Yes, you're right about the contrast difference - I'll have to investigate this a little further. I've downloaded raw files from other camera (NIKON, CANON and even OLYMPUS) and they have no such artefacts (mesh) when processed in PW with the same settings.

The overall effect of the mesh is that the image looks washed-out - I have to increase the color saturation quite a lot. Apart from this there is not much difference in 1:1 view so maybe these artefacts are not that important anyway...

Once again thanks for your answer.

Bogumil

Raw digital camera images generally do have low saturation. So increasing saturation by aound 20 - 30% is normal. You can include this saturation boost in your camera default settings and thus make it automatic when you open an image in the raw dialog.

Kiril

I briefly had access to Olympus RAW (.ORF) files, so I tested them in PWP; using both VNG and AHD interpolations. I don't see the 'mesh' that Bogumil has seen. Perhaps it's a specific sensor/camera/RAW processing combination.

I'm not sure if this is helpful, but at 4:1 seems to be a bit of pixel microscopy with little bearing on the actual print/display quality. There is also a display pixel aliasing at more than 100% zoom: some apps smooth it, some use faster (e.g. nearest neighbor) upsampling which may cause apparent pixelation.