Does playing in lower-than-native resolution add lag?

[Prognathous]

For example, does a QHD screen add lag when used in FHD (due to having to constantly interpolate the picture)?

Thanks!

 

[XoR]

it entirely depends on how scaling is done, if it uses large memory buffers to store frames or not. It is possible to scale image using only very small amount of memory and that is certainly possible in the case with 1920x1080 to 3840x2160 scaling.

Large memory buffers (so large input lag) are needed only to do 1:1 pixel mapping and adding black bars on top and bottom of screen (such as displaying 1080p content on 1920x1200 screen). In perfect world monitor could be done in such a way that if it stretches to full screen or only add bars on left and right it doesn't add input lag too but in reality all displays which have memory buffer use it even in native resolution, even if that is totally retarded way to make monitor. Conclusion is that non-native resolutions do not add input lag in this cases.

If display have simple scaler that do not have large memory buffer it doesn't add any (noticeable, let's say >1ms) input lag in either native resolution or non-native thus it doesn't add more input lag in non-native resolutions.

It is possible that there exist display that have different input lag depending on resolution and scaling option used so I cannot give definitive answer. It is very highly unlikely you will ever find such monitor. Most either have input lag or do not have it regardless of resolution used.

 

[Prognathous]

Thank you. This is very good to know. One less reason for me to avoid a QHD screen now

 

[wildpig1234]

I kinda have this question myself a while too. Since many methodologies currently involving testing input lag on 4K monitors are not done at 4K and usually at 1080. But I would imagine any difference that might exist is probably neglible...