Position of "Profiled Lens Correction" in the Toolchain Pipeline

Hey people!

What is the position of “Profiled Lens Correction” in the Tool chain Pipeline? Thank you.

Regards,
Gokul PM

Have a look here: Toolchain Pipeline [RawPedia]

So, as expected, rather early: Step 7

BTW: Welcome to Pixls!

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Hi @Jade_NL,

Thanks for the prompt response. Appreciate your help here.

By Step 7 in the [Toolchain Pipeline - RawPedia], did you mean Step 1.7 i.e Lens distortion correction or is it before Step 7 i.e Convert colorspace?

Regards,
Gokul PM

Yeah, step 7 is a bit ambiguous… Although somewhat self explanatory :grin:

Block 1 (Preprocess), step 7 - Lens distortion correction

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Hi @Jade_NL,

Thanks for the clarification!

Also, thanks for the welcome. It’s been nothing but total delight working with RawTherapee so far. Thanks to everyone who made this happen :slight_smile:

Sorry to bother you again. Yes, although your answer was self-explanatory ( 1.7. Lens distortion correction), I was confused of its position (i.e before the Demosaicing step) for the following reasons:

  1. “Distortion correction” is a separate tool in Transform module, I was not sure if the Step 1.7 refers to the standalone tool or the distortion correction that is part of “Profiled Lens Correction”.

  2. There is already a “Chromatic Aberration Correction” applying as part of Raw module before the Demosaicing step.

  3. Wasn’t “Vignette Removal” supposed to apply at Step 15.6?

  4. Transformations and Crop as part of the lens profile corrections happening before Demosaicing was a tad confusing as well, because transformations and crop as individual tools are supposed to apply after Demosaicing.

Thanks & Cheers
Gokul PM

I am under the impression that everything mentioned under the Lens / Geometry section in the Transform tab is to be found in the Preprocess (block 1) in the pipeline. Not everything is mentioned by the specific name as seen in RawTherapee though.

Step 15.6 points to the Vignette Filter, found under the Exposure tab. This doesn’t have anything to do with the actual lens used, but is more of an artistic option (although, technically, can be used to mitigate vignetting as well: poor mans vignetting).

I’m not one of RawTherapee’s developers so I cannot tell you why certain choices where made the way they are. Maybe @heckflosse, @Thanatomanic or one of the other devs/maintainers can enlighten you.

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Thanks for your time @Jade_NL!

Definitely makes more sense now. I shall place the “Profile Lens Correction” in my workflow accordingly.

Also, appreciate it if anyone wants to contribute their views as well. It will only improve our clarity on this subject. Thank you.

Regards,
Gokul PM

I found the lensfun dev docs to be just a bit informative; they beg one to apply the corrections while the image is still in linear tone space. I’m not sure what influence that has to the interpolation-based corrections, distortion and CA, but for vignetting, a tone correction, the starting point needs to be anchored, and linear is a good anchor.

Musings of a bear-of-little-brain… :crazy_face:

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The sequence of RT tools used in your workflow is not important. They are always processed in the sequence defined by the toolchain.

Great to know about this