Lightroom 9.4: before/after view in Develop slow

[#1]

Since a while, when I'm in Develop and switch to before view (with \ key), this will take several seconds. Same when switching back. I recall this being much faster before.

I have an Apple iMac 2017 5K, with a 3.8 GHz Quad-Core Intel Core i5 and 40GB RAM.

I am running Lightroom on my internal SSD (catalog and photo's)

I have set the camera RAW cache to 60GB or something

GPU is enabled (custom setting)

I have optimized my catalog

Regular edit are running fine as far as I can tell, it is the before/after view that slowed down.

Am I overlooking something?

[#2]

Since a while, when I'm in Develop and switch to before view (with \ key), this will take several seconds. Same when switching back. I recall this being much faster before.

I have an Apple iMac 2017 5K, with a 3.8 GHz Quad-Core Intel Core i5 and 40GB RAM.

I am running Lightroom on my internal SSD (catalog and photo's)

I have set the camera RAW cache to 60GB or something

GPU is enabled (custom setting)

I have optimized my catalog

Regular edit are running fine as far as I can tell, it is the before/after view that slowed down.

Am I overlooking something?

[#3]

Please try switch off the GPU support from the Lightroom preferences and check if that helps to fix the issue

Go to Lightroom > Preferences > Performance tab > Uncheck "Use Graphics Processor" > Restart Lightroom.

Adobe Lightroom GPU Troubleshooting and FAQ 

https://helpx.adobe.com/lightroom-classic/kb/troubleshoot-gpu.html

[#4]

Switching off GPU support does not make  much difference.

The strange thing is, I can do some edits (for example reducing highlight value and adding clarity) and switching between before/after is fast. If I do one extra edit (for example crop), switching between before/after becomes slow. And it remains slow, even if I undo the crop.

I am very sure, that switching between before after was always fast some time ago.

[#5]

It is getting stranger. I noticed that before/after switching was still quick on photos I edited a few months ago.

I also noticed that my default RAW settings (or develop settings) were different. For example, the default value for sharpening was higher (40) than before (25). So I made a new set for RAW defaults and imported an already imported photo again with a different filename. I applied the same changes and to my surprise switching between before/after is quick again. When I go the the other (duplicate) photo before/after is still slow (with beachball).

So how do I go from here? Do I have to re-import my last set of photos to solve the problem? (I am not enthousiatsic about that as I already edited photos). Or is there a better solution?

[#6]

Look at the History oif edits for the image/images that are slow. Is there any Adjustment Brushing going on?

[#7]

No, no adjustment brush. Just some straightforward edits like clarity, brightness, saturation, shadows and occassional cropping.

All my edited images from the last import are slow when switching between before/after. I checked images I edited last year, and all of these are fast (even those with adjustment brush).

[#8 · Accepted solution]

Well, I ended up re-importing the photos as this was the only thing that solved the problem.