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Author Topic: How do the local adjustment tools fit into the pipeline?  (Read 1281 times)

NateWeatherly

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How do the local adjustment tools fit into the pipeline?
« on: August 13, 2021, 07:28:40 pm »

I’ve noticed that under certain conditions adjustments made using the local adjustment panel (with, say, a gradient that opaquely covers the entire image) give different results than the corresponding basic tools. For instance, with Adobe’s standard profiles the effect of the WB sliders seems comparable, but with custom profiles they can give quite different results in terms of hue and saturation. Also, the exposure slider sometimes seems to handle highlight rolloff differently than the basic panel exposure. Does anyone know how the math or pipleline position of these tools differ?

Thanks!
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digitaldog

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Re: How do the local adjustment tools fit into the pipeline?
« Reply #1 on: August 13, 2021, 07:57:58 pm »

So no one outside Adobe (and few inside) can describe the math. Or will do so publicly.
Camera Profiles are white balance agnostic by design. But they do report a CCT Kelvin value (a pretty large range of possible colors) differently so seeing said numbers change is expected.
Highlight roll off is an attribute of the Process Version, there may be other areas that affect this too.
Stuff you alter, alters the image rendering and what you see. I am not sure why knowing what is happening under the hood matters as long as you get the color appearance you desire.
The order of edits doesn't matter, Adobe processes the edits in the order they deem ideal. IOW, it isn't user applied order. Of course, there are edits you can make that allow you to get to a goal faster and in general, the recommendation is to work top down, left to right (depending on ACR or LR's layout of controls), but you can work in any order you desire.
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NateWeatherly

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Re: How do the local adjustment tools fit into the pipeline?
« Reply #2 on: August 13, 2021, 09:44:43 pm »

Thanks for your reply. Admittedly, I am digging much deeper into the inner working of Lightroom than is necessary for the average user, but I’m working on creating some custom profiles/presets to do some pretty unorthodox things (could almost say I’m trying to “hack” custom profiles to do things that Lightroom isn’t really meant to do) and I’m finding it necessary to understand where the various tools are operating within the pipeline in relation to the various parts of the profile (and exactly what sort of data they are operating on) in order to make the profiles as powerful as possible. It’s clear to me that some of the selective edit tools are either not working on the same image at the same point in the pipeline or performing slightly different transforms. For my purposes, for instance, it makes a difference whether the tools are working on the image before or after the profile look table, hue-sat map, and calibration panel. So, right now, what I’m trying to figure out specifically is how the WB and exposure sliders relate to the image vs the basic panel sliders. I suspect that while the basic panel wb sliders are working on the pre-demosaic image and are subject to an interpolated chromatic adaptation adjustment (based on the profile color matrices), perhaps the local adjustment white balance is applied after debayering and without chromatic adaptation, etc. You’re definitely right that nobody seems to know the details on this kind of stuff! I’ll try to come up with some experiments to figure it out..
« Last Edit: August 13, 2021, 09:54:24 pm by NateWeatherly »
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digitaldog

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Re: How do the local adjustment tools fit into the pipeline?
« Reply #3 on: August 13, 2021, 09:47:53 pm »

You can try the various SDK's on profiles and such, more than that, I seriously doubt anyone else here can provide more detail. You can of course try contacting the Adobe team, maybe Eric Chan but of course, there is all kinds of stuff he's never going to tell anyone outside Adobe.
https://www.adobe.com/go/dng_sdk
https://download.adobe.com/pub/adobe/lightroom/profile-sdk/ACR_and_Lightroom_Profile_SDK.zip
https://wwwimages.adobe.com/content/dam/Adobe/en/products/photoshop/pdfs/dng_spec_1.5.0.0.pdf
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NateWeatherly

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Re: How do the local adjustment tools fit into the pipeline?
« Reply #4 on: August 13, 2021, 09:55:41 pm »

Thanks!
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JRSmit

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Re: How do the local adjustment tools fit into the pipeline?
« Reply #5 on: August 14, 2021, 11:28:57 am »

I’ve noticed that under certain conditions adjustments made using the local adjustment panel (with, say, a gradient that opaquely covers the entire image) give different results than the corresponding basic tools. For instance, with Adobe’s standard profiles the effect of the WB sliders seems comparable, but with custom profiles they can give quite different results in terms of hue and saturation. Also, the exposure slider sometimes seems to handle highlight rolloff differently than the basic panel exposure. Does anyone know how the math or pipleline position of these tools differ?

Thanks!
One thing I noticed that apparently different behaviour (like you mention) stems from the basic raw  exposure level. Under exposed vs optimal-exposed or over-exposed.
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digitaldog

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Re: How do the local adjustment tools fit into the pipeline?
« Reply #6 on: August 14, 2021, 11:38:01 am »

One thing I noticed that apparently different behaviour (like you mention) stems from the basic raw  exposure level. Under exposed vs optimal-exposed or over-exposed.
Nothing in ACR or any other raw converter or software has any effect on Exposure (despite silly names for controls).
Nothing in ACR tells you about actual exposure. I wish it did, it could but alas, there is no raw Histogram and even if it did, that toothpaste is out of the tube.
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jrsforums

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Re: How do the local adjustment tools fit into the pipeline?
« Reply #7 on: August 14, 2021, 12:43:37 pm »

Nothing in ACR or any other raw converter or software has any effect on Exposure (despite silly names for controls).
Nothing in ACR tells you about actual exposure. I wish it did, it could but alas, there is no raw Histogram and even if it did, that toothpaste is out of the tube.

As you said earlier, Adobe does not release the ‘math’ on what the controls do.  If I remember correctly, from early LR discussions, the ‘Exposure’ (brightness) slider (and other) apply other adjustments, such as roll-off, etc. that are non-linear.  They, therefore, could provide different effects for similar images taken at, say, 0, -2, & +2 EC.

Would appreciate your thoughts.
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John

digitaldog

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Re: How do the local adjustment tools fit into the pipeline?
« Reply #8 on: August 14, 2021, 12:53:31 pm »

Not sure what additional thoughts I can add. Many of the controls are “non linear”.
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jrsforums

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Re: How do the local adjustment tools fit into the pipeline?
« Reply #9 on: August 14, 2021, 01:10:04 pm »

Not sure what additional thoughts I can add. Many of the controls are “non linear”.

That’s what I understood.

So, for want of possibly better words, the’quality’ of the exposure….causing greater or lesser (or negative) application of the sliders could effect the look of the image you could get….vs. same image ‘exposed’ differently.
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John

digitaldog

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Re: How do the local adjustment tools fit into the pipeline?
« Reply #10 on: August 14, 2021, 04:23:51 pm »

That’s what I understood.

So, for want of possibly better words, the’quality’ of the exposure….causing greater or lesser (or negative) application of the sliders could effect the look of the image you could get….vs. same image ‘exposed’ differently.
The overall "look" maybe, the data no. Yes, you can actually under expose a raw (many do) and increase brightness to it doesn't appear under exposed. The underlying data, the amount of noise will differ.
You can under expose transparency film too. And push it in film process. That too will affect the over all quality.
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