I have to correct myself - I have incorrectly specified the connection between the Laptop and the external monitor. It is actually an USB-C to DisplayPort adapter.
What could be the cause/possible solutions to my issue?
If I look up the specs of this computer on the Dell website, it says that the monitor is HD (1920x1090), not 4K.
Why do you think your internal monitor is 4K? What is the number of pixels in this monitor?
Not being able to work smoothly with a 4K monitor is a known issue with Lightroom 5.7.1.
thanks for the reply.
The Dell XPS15 9550 is available with two different internal displays. My laptop's configuration has an internal 4K display (InfinityEdge 4K-Touch-Display, 15,6'', Ultra HD 3.840 x 2.160).
Please refer to http://www.dell.com/de/p/xps-15-9550-laptop/pd?oc=cnx5505&model_id=xps-15-9550-laptop to confirm my information if you like.
So my original question remains: What could be possible reasons that Lightroom 5.7.1. works perfectly wenn on my internal 4K display (from which fact I take the conclusion that my laptop's specs like CPU, RAM and SSD drive speed are sufficiently fast to handle 4K), but with my external 4K monitor it is very sluggish?
I suppose it must have something to do with the adapter that I am using (USB-C to DisplayPort) and/or a driver problem?
Thanks in advance,
...before anyone asks ... yes, I have updated all my drivers to the latest availabel versions
I think the problem is that Lightroom 5.7.1 does not work well with 4K monitors and there's nothing you can do about it except upgrade to Lightroom 6 and get a high end graphics processor.
Thanks again for your reply.
As I said, Lightroom 5.7.1. works perfectly well with my graphics processor and the internal 4K display. So I don't really agree with your logic...
Anyways, thanks for the effort to help.
Any other ideas out there?
I am assume you are using both screens at same time?
The laptop most likely has two video cards.
Check to see if your results with the LCD/monitor are both using the same video card.
When you connect the external monitor it may be using the on-board Intel video vs Nvidia card?
and/or there is not enough video RAM to run both QHD screens simultaneously.
If you are using both screens:
You could try disabling the laptop LCD to see if you get the speed back with just the external.
I am not sure if you can have the internal LCD independently run off the Intel video and external off the Nvida or not.
- yes, I already checked if disabling the internal display would improve speed on the external one. It did not change anything however
- I am quite sure that both displays are driven by the same driver since both show up in the intel graphics driver display selection and for both, things like resolution and frame rate can be selected in the intel driver configuration tool, none of them require to use any nvidia tools...
Solution: I upgraded from Lightroom 5.7.1 to Lightroom 6, and now the problem is solved, and the speed is satisfactory.