Position of "Profiled Lens Correction" in the Toolchain Pipeline

Software RawTherapee
1

Hey people!

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

Regards,
Gokul PM

2

Have a look here: Toolchain Pipeline [RawPedia]

So, as expected, rather early: Step 7

BTW: Welcome to Pixls!

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3

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

4

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

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

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5

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

6

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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7

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

8

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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9

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

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10

Great to know about this

11

Why is the sequence of RT modules not important in a work flow?

Example 1:

Step 1: Enable “Black and White” in Color section
Step 2: Enable “HSV Equalizer” in Color section
Step 3: Edit the “Value” equalizer in the “HSV Color” section

Going by your comment, if the sequence of modules in a work flow is not important, then when we change the “Value” equalizer, it should not have an effect, because we used the “HSV Equalizer” module after the “Black and White” module.

Example 2:

Step 1: Import a photograph with a lot of Enable "chromatic aberration
Step 2: Change the “False Color Suppression Steps” in the Demosaicing module
Step 3: Enable “Auto-Correction” in the “Chromatic Aberration Correction” module

According to the Toolchain Pipeline, the chromatic aberration gets corrected before the “False Color Suppression Steps” in the Demosaicing module. So when we are working with false colors in Step 2, we are actually working with the output of Step 3.

Another example would be to perform processing related to color corrections and then finally modifying the “White Balance” module. It works, but it’s better to process the “White Balance” before we start working on the colors.

In my humble opinion, it introduces a lot of inconsistencies (unable to predict or ascertain the output of a module) if the work flow is not in sync with the tool chain pipeline. Many a times, it involves back tracking because I did not consider into account the effect of a Y module on X module when I adjusted X module before the Y module, but in toolchain pipeline Y module comes before X module. Ofcourse, this does not apply to all the modules, just the ones whose functionalities coincide.

Kindly add if you have any thoughts on this, it will only help expand our perspective in this regard. Thank you.

Regards,
Gokul PM

12

Have a Look here Toolchain Pipeline - RawPedia

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The pipeline is fixed, so you can know which module comes before another. Of course the output of those prior modules influences the input for the current module. So if you make a late change to a module early in the pipeline, you will get accumulated effects. That’s the nature of any pipeline.
But you are completely free to choose when you make edits. RT does not restrict you to make your edits in the same order as the processing pipeline. That’s an important distinction.

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