P: Large numbers of brush strokes leads to slowdowns and can cause an image's edits to reset.

[C.Cella]

In Lightroom it is impossible to edit a photo as much as we want or need, using Masking regardless of the hardware you have.

EXPLANATION 

Let's say you want to edit a photo with Masking to your heart's content OR because you need to change many aspect of the photo.

Logic tells you "we have Masking so obviously it's possible to do masking safely and as much as I want"

Reality is that in Lightroom Classic there is an "upper limit" of local edits that we can have on a photo: once we reach that "upper limit" the photo will be be reset.

So in Lr it's not possible to sue Masking as much as we want/need.

Usually if you have lots, lots of edits on an image other editing software struggle and get progressively slower and slower (if one has powerful hardware generally slowdowns don't happen or appear later) but in LR a photo can reach a point where it's no longer editable and it will be reset NO MATTER THE HARDWARE YOU HAVE.

All Masking tools (gradients, spot removal, brush, Ai, et...) contribute to reaching this "upper limit" of local edits BUT Brush is the tool that contributes the most because each strokes is made of countless of dab points that are heavy to process.

Here I have attached a preset for everyone to use.
Apply it on one of your photos that already has Masks and your photo will be reset. (Please be sure to undo, or use another another history step or Snapshot to revert back to your safely edited photo)

This "Reset Bug" is a huge problem/limitation AND as long as it exists we users will never, ever be able to use Masking as much as needed/wanted in Lr.

For the record this issue is not present in Adobe Camera Raw or other non Adobe softwares: it is totally unique to Lr.

As far as I have tested we can have "infinite" number of local edits in ACR...logically with many, many mask ACR becomes progressively slower but there is no photo reset.

Best Practice When Working in ACR and LrC using Masking

If you are doing Masking in ACR and import the photo in LrC (or import settings form disk if the photo is in the LrC catalog) then the photo will either be slower to edit OR be reset in LrC.

If a photo is resetting in LrC then you must go one step back beore the reset after that you can finish editing it in ACR but unfortunately you can't safely open/import that photo in LrC again as the edits will be unusable by LrC

Keep a Virtual Copy in LrC before you edit in ACR or import form ACR.

That Virtual Copy will be always usable in LrC.

Best Practice with Brush Tool

1. Create a new Brush Mask for every single stroke you do. This way you can delete the stroke(s) that you don't like, redo them better and go back to an editable photo when the reset happens.
2. I recommend to ONLY use Subtract as and never user Erase Brush that adds dab point but are not visible in the overlay. Subtractions are always visible in the overlay and can be deleted.
3. If you are working with Brush Density I recommend to ALWAYS keep the same Brush Density in the same Correction and ideally write it in the Correction's name. On the same correction a new brush with different Density will overwrite the previous stokes adding more dab points above the ones created but in the overlay it looks like you did fewer. It you find a that a brush at the current density is not giving you what you want then: create a new correction > use the same settings AND use Brush with a different Density in that correction.

I personally work with very low flow and keep always Density at 100 for all my corrections. When is see that a brush is not enough or too much and is not giving me the result I want I: delete it > create a different Correction with  higher/lower different settings and brush there but the Density is always at 100.

P.S.
I was the first to discover and report this back in 2017 in this thread. (The username is different but it's me)
I bring it back as a full fledged Bug Report upon request of the Adobe team so please moderators do not merge this with existing Bug reports as this needs to be traceable as a standalone.

[Alle_W]

Update:

I did all the steps and sadly, it did not work 😞

[Bob Somrak]

A couple threads.  This is an issue acknowledged by Adobe.

As a test, if this is a RAW file, when this happens go back a step in history and then do a Menu Photo/Save Metadata to File.   How big is the XMP that is created?  For the one person I know that upload a file that this happenen on the XMP was over 12MB!!!!!!  The issue was completely repeatable with that file.  

https://feedback.photoshop.com/conversations/lightroom-classic/lightroom-cc-20154-adjustment-brush-s...

https://feedback.photoshop.com/conversations/lightroom-classic/lr5-adjustment-brush-resets-all-devel... 

[Alle_W]

I read the two treads you linked, and it sounds exactly like what happened to me

Yes i work with RAW files. The XMP is 22 MB. 

[Bob Somrak]

Wow! i thought a 12MB XMP was huge.  i cant imagine what is in a 22MB XMP.  

[U2Fan61]

Hi

I am experiencing very odd behaviour when using the adjustment brush.

I have used the brush to lighten text on a gravestone. This worked well but has stopped working for some reason.

Every time I try to make a new brush stroke, Lightroom resets all my previous edits back to Import.

This is very frustrating as I was just finished brightening the text.

I use a Wacom tablet and have disabled touch and side buttons but this has't helped.

Any suggestions other than restarting Lightroom and PC as that hasn't helped either.

Thanks in advance

[U2Fan61]

Using latest version of LrC 10.1.1, updated yesterday evening

[DdeGannes]

Revert to LrC 10.0.

[U2Fan61]

Thanks, I will give that a try.

That might just do it :-))

[U2Fan61]

Sorry to report that reverting to LrC version 10.0 hasn't helped.

Exactly the same behaviour from Lightroom.

I have tried creating virtual copies to reduce the number of the history states/records but this hasn't helped either.

Any other suggestions?

Thanks in advance.

[Bob Somrak]

As an experiment, do the same edits with a mouse.

[Bob Somrak]

See here.  Do the Save XMP experiment in the thread and report the size of the XMP

https://community.adobe.com/t5/lightroom-classic/brushes-delete-all-edits-on-photo/td-p/11818400 

[Alle_W]

I tried the built-in mouse pad on the laptop and i got the same result 😞

But i suspect the "reset crash" has to do with to mutch edit on a singel photo. 

[Bob Somrak]

If you add a new edit with the mouse to the same photo it will do the reset.  What I meant was to

Create a virtual copy.

Reset/delete the 3 or 4 brush strokes.

Do the 3 or 4 brush strokes with the mouse.

It issue may be how many brush Dabs are created with the Tablet.

[U2Fan61]

Thank you Bob for your suggestion.

I believe that it has something to do with the number of brush strokes.

I used one of the virtual copies that I had made earlier and deleted the adjustment brush with all the brush strokes. I then created a new adjustment brush to finish adjusting the last few letters on the gravestone. I could complete the adjustments without any problem. My plan is to open both versions of the image as layers in Photoshop and then blend the two adjustments.

A bit of a work-around but hopefully it will work as planned.

I will also look at the other suggestions tomorrow.

Again, many thanks for your time and assistance.

Cheers

[U2Fan61]

Thank you for your suggestion, Denis.

I may have run into several issues, which I will look into tomorrow.

I recently activated GPU acceleration and maybe this has played a role in the isuue.

I also updated LrC yesterday, but reverting to LrC 10.0 hasn't solved the issue.

I suspect that the issue was caused by the number of brush strokes.

You can read my reply to Bob in the thread below.

Again many thanks for your time and suggestion.

Cheers

James

[Alle_W]

I tried it too but got the same result.

The problem does not happen until after MANY brushstrokes.  And it does not seem to matter if it is with mouse or tablet.

[Rikk Flohr: Photography]

setting status to Investigating

[defaulte1bptwq3szfa]

Hi,

I've created a complicated mask with the brush tool. It's not finished, but whenever I try to add extra masking to it, Lightroom resets all masks that are applied to the photo.

I had a conversation with technical support and we went through reinstalling and resetting Lightroom to see if it would help, but it didn't. Please look into this.

Video to show what happens:

https://www.youtube.com/watch?v=xtOv4B0gB8M

[GoldingD]

THis is not a direct fix of your issue. BUT

From your video, it looks like you are using LrC v11, You may want to upgrade to v12, Changes/additions in masking, starting with auto object. for this photo.

[Rikk Flohr: Photography]

As a test, it might be good to try this same mask in Camera Raw. Does it fail similarly? At the same place?

And, as @GoldingD  says, you could try updating to LrC 12 also. 

[defaulte1bptwq3szfa]

I have since then upgraded to Lightroom 12. The issue still persists. I've tried object masking, but it's not precise enough for what I want to achieve.

[defaulte1bptwq3szfa]

It would take me ±2 hours of manual masking if I was going to try that so that's not preferable. Unless there's a way to duplicate a mask from Lightroom to Camera Raw? I believe it's happening due to many small details that are getting masked.

[Rikk Flohr: Photography]

Export the partially finished image as a DNG and then open the DNG in Camera Raw and pickup where you left off. It will tell us more about the failure if we see it happening in Camera Raw.

In fact, could you send a copy of the DNG created right before it fails?

[defaulte1bptwq3szfa]

Sure thing! https://drive.google.com/file/d/1wHE0ck9ePvmKC8P3Pkn0bueyttvbM0Ng/view?usp=sharing There's the dng of the photo. The error especially occurs when expanding mask 6 with the brush tool.

[Rikk Flohr: Photography]

I got it - thanks!

I see the same failure mode in LrClassic and am going to test in Camera Raw to see if the failure is in the raw engine.  I will update this thread when I have more information.