I would guess they are low-resolution compared to the monitor, right, perhaps 1920x1080 (2K), or do you mean something else?
Yes in the slideshow it seems that the resolution is something like 2k.
I don't know the exact resolution of the slideshow, but the quality is very different (poor) from what I can see for example in "develop"
I save the photos in raw + jpg format from my Canon 6D and when I import the files in LR, inside library and develop, I view only one (the raw I suppose), and everything is ok
is it possible that for the slideshow LR use a JPG format instead of the RAW format ?
Where are the parameters to configure the behavior of slideshow ?
Try increasing the default preview size for your catalog in Catalog Settings. For a 5K screen you probably have to be at the highest setting. You also should try generating 1:1 previews of the files. That should also take care of it.
In the catalog settings the standard preview size is the highest (2880 Pixel) and also the generating 1:1 preview si active...
Did you actually generate the 1:1 previews? This has to be done manually using the Library->Previews->Build 1:1 Previews menu item while you have the images selected.
Yes, I manually generated the 1:1 preview. If I try again LR replies that all the previews are yet updated.
In Library or Develop previews the quality is astonishing but in slideshow is only "normal"...