Chromatic Aberration and Defringe

[Fabien]

Hi there,

I wanted to ask if there was any plan to add Chromatic Aberration and Defringing directly in PTGui.
Having to do this extra step in another software is tedious. I also noticed that since most RAW softwares only export Tiff 16bits integer, you do lose precious luminance information in some cases for accurate HDRI creation.
RawTherapee can export Tiff 32 bits but the HDRI created by PTGui looks washed and and desaturated in comparison to RAW directly fed to PTGui.


PTGui using RAW


Using Tiff 32bits from RawTherapee with sRGB working profile

I know PTGui reads 32bits files as linear gamma, so I tried to export from RawTherapee with gamma at 1.0. Color and gamma seems better, but PTGui then failed pretty badly at blending the highlights.



Does anyone have tips about how to prepare the images correctly in RawTherapee?
And can we expect to not have to do all that in the future? It looks like Libraw supports chromatic aberration correction.

Thanks!

[Fabien]

I found this amazing presentation that seems to answer my question: https://www.slideshare.net/KurumiUranishi/hdri-production-technique-with-high-reliability
Slide 132 mentions that the final image is using the camera native gamut, which explains the desaturation / lack of contrast I was experiencing.

[PTGui Support]

Hi Fabien,

On 23/02/2023 13:50, Fabien wrote:
> Hi there,
>
> I wanted to ask if there was any plan to add Chromatic Aberration and
> Defringing directly in PTGui.

This is on the wish list. I can't say if or when this would get added,
I'm sorry.

> Having to do this extra step in another software is tedious. I also
> noticed that since most RAW softwares only export Tiff 16bits integer,
> you do lose precious luminance information in some cases for accurate
> HDRI creation.

I think 16 bit is plenty; raw files only have 12-14 bits of depth. And
if you're bracketing, bit depth is even less important.

> RawTherapee can export Tiff 32 bits but the HDRI created by PTGui looks
> washed and and desaturated in comparison to RAW directly fed to PTGui.

Yes this is normal. A hdri records true light intensities but that does
not make a pleasing image, you need to add a bit of contrast. PTGui does
this in the Post Processing tab when you load a raw image.

> I know PTGui reads 32bits files as linear gamma, so I tried to export
> from RawTherapee with gamma at 1.0. Color and gamma seems better, but
> PTGui then failed pretty badly at blending the highlights.

This looks like what happens when bracketed images are loaded in PTGui
where the metadata doesn't match the actual exposure.

For example, if you load 2 images, one at 1/50 and the other at 1/100,
then the former should be twice as bright. If you make individual
adjustments in the raw converter, for example brightening one image and
darkening the other, then PTGui gets confused.

> Does anyone have tips about how to prepare the images correctly in
> RawTherapee?

I would just use 16 bit output from RawTherapee. Disable all
adjustments, except for noise reduction and CA correction.

> And can we expect to not have to do all that in the future? It looks
> like Libraw supports chromatic aberration correction.

This looks to be rudimentary and manual, I doubt this would work in
practise, something better would probably be needed.

Joost

[Fabien]

Thank you for your answer. I think I've been chasing several problems at the same time, which made it pretty confusing. I thought that 32bits from RawTherapee would hold the same range as the RAW files, but highlights clipping still occur. Only the RAW contains the 12-14 bits depth from what I can see?
I have figured out the difference of contrasts between PTGui + Raw and PTGui + RawTherapee TIFFs 32bits, it was mostly a different base exposure. The difference that I have left probably has to do with color profiles, as mentioned above.

You are mentioning the Post Processing contrast curve applied to the RAW files, but this is not added to the HDR output, is it?