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“Erase” brush is actually a normal brush with "Density" set to zero!

Joined
Jul 3, 2019
Messages
16
Location
Sintra, Portugal
Lightroom Experience
Intermediate
Lightroom Version
Classic
Lightroom Version
Release 9.2.1 "Classic"
Operating System
Windows 10
This is not a question but a “For Your Information” post based on my latest experience (and previous ignorance) on how the Local Adjustments are rendered in Lightroom.

Since Lightroom is a parametric editor, the more detailed the Local Adjustments are, especially with multiple and intricate brush strokes, the slower everything gets; mainly because the brush strokes are actually built up with multiple overlapping “dabs” or points. It does not even support lines. Lines created with the “Shift” shortcut are also multi-point renderings.

So, in my ignorance in wanting to improve performance, I decided to create large “dabs” and then proceed to erase areas with the “Erase” brush; but to my dismay things were just as bad and in a few cases it actually got slower, and the XMP files got larger.

In turns out the “Erase” strokes don’t erase, but actually paint over with more multi-point “dabs” but with the "Density" set to zero. That’s right, using the “Erase” brush is the same as just brushing over with the zero density. Even when the “Erase” brush is large and completely “covers” and underlaying smaller “dab”, it does not remove it and is still there adding to the processing difficulty.

Also, as a side note, this is also the reason why when using the Graduated or Radial Filter, the brush strokes don’t restore the filter after using the “Erase” brush, but instead just “paint” normally. In other words, the “Erase” is not erasing but just brushing normally with a zero density.

I discovered all this while analysing the XMP data that is generated for the local adjustments, and found that Lightroom generates plenty of extraneous “dabs” and is very inefficient.

For some of my “heavier” edited photos, I decided to edit the XMP file in a text/code editor (since it is just plain XML code), and did some manual clean-up in order to reduce the complexity and inefficiency of the generated code and then just had Lightroom read the file back into the catalogue. That improved the rendering speed quite a bit in some cases.

Yes, I know I can do use Photoshop for the more complex editing, but I like having everything in Lightroom (and I am also not very proficient in Photoshop).

So, I hope this information is useful to someone, or maybe it has already been discussed here, and none of this is new to most of you! Anyway, hope it helps!
 
Joined
Jul 3, 2019
Messages
16
Location
Sintra, Portugal
Lightroom Experience
Intermediate
Lightroom Version
Classic
It's quicker to just clear history once you're happy with changes, this speeds up for a heavily edited photo.
Yes, that also helps, but it's not exactly the point I'm referring to here! The fact that the "Erase" is actually just more brush strokes on top, and that the brush strokes are multi-points, and that they have to have about 60% overlap in order to look continuous, makes the whole process very inefficient.

However, now knowing how it all works, makes me "think" and plan out how I edit and apply the brush strokes. It also allows for future possibilities of using an external editor on the XMP data (or maybe a plug-in will be able to do it) and build up Polygon Fills, which Adobe still has not provided.

PS! Sometimes, using the AutoMask or the Range Mask, is just not feasible!
 
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