P: Need more settings for standard preview sizes

[FeedbackCommunityMember]

I am surprised to see that there are very few relevant standard preview size settings for people using a 4k monitor. The maximum setting is 2880px and then "Auto". Lightroom is choosing 6720px on the "Auto" setting which is massive and (I presume) contributing to Lightroom running extremely slow. This is all while running a brand new 16" Macbook Pro with 32gb of RAM, AMD Radeon Pro 5500M 8 GB, and 2.3 GHz 8-core i9 processor.

Please include more preview size setting in between 2880px and 6720px for people working on 4k monitors.

[John R Ellis]

"lightroom is choosing 6720px on the "Auto" setting"

That sounds like a bug. Usually the Auto setting chooses a size that's the width of the display or a little larger.

[Bob Somrak]

I agree with John Ellis is looks like a bug

On my iMac with a 5120pix width display, Lr sets Auto to 5120.  You MacBook Pro 16 should set it to 3072.

[JohanElzenga]

I agree this is a bug. It has something to do with how high resolution is scaled by the OS. Suppose you have a 5120 pixels wide screen. You probably do not use this resolution in your OS, because that would make menus and buttons tiny. So let's say that you choose a resolution setting of 2880 pixels wide. In MacOS that would probably be presented as 'More Space'.

Now let's look at what happens behind the scene. If applications would simply draw their interface items at that 2880 pixels wide resolution, these items would then be upscaled to 5120 real pixels on screen and that would look ugly and soft. So the OS asks the application to draw the interface items at twice this resolution (5760 pixels wide), so it can downscale them to 5120 pixels. Depending on the resolution you choose, the OS may ask the apps for an even higher resolution.

Lightroom should ignore this for its previews, and always render standard sized previews at the same (hardware) resolution, but it does not. Try this: change the OS display resolution to a few different settings and each time check what Lightroom shows for 'Auto'. The 'Auto' preview size should not change, because the hardware resolution of the screen obviously does not change. But Lightroom does change the 'Auto' setting each time...

I reported this a long time ago, but apparently the report got lost. I reported it again.

[edmundgall]

On my iMac 5K with Display settings at Scaled/More Space, LR Classic Standard Previews (High Quality) are set to Auto and showing 6400px in size.

macOS Mojave 10.14.6
LR Classic 8.4.1
Camera Raw 11.4.1

[Bob Somrak]

It must be a bug on Mac when you don't have the display set for "Default for display". My 27inch iMac is set at "default for display" and I get 5120 which is the Native display pixel width.

[JohanElzenga]

'Default for display' is often 50% of the hardware resolution. Twice that is the hardware resolution again, so that is what 'Auto' will give you.

[Bob Somrak]

As usual you are correct Johan.  I changed it to "more space" and I get 6400 like Edmund.  

[JohanElzenga]

My record stands at 7680 pixels. Can anybody beat that?  😉