# Lumen rendering latency / refresh rate in real time ?? **URL:** \ **Category:** Rendering\ **Tags:** unreal-engine, Global-Illumination, Lumen\ **Created:** [June 18, 2023, 8:18pm UTC](https://forums.unrealengine.com/t/lumen-rendering-latency-refresh-rate-in-real-time/1203410 "2023-06-18T20:18:05Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![WBDeSportVaL](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/wbdesportval/32/718785_2.png) [@WBDeSportVaL](https://forums.unrealengine.com/u/WBDeSportVaL)\ **Post date:** [June 18, 2023, 8:18pm UTC](https://forums.unrealengine.com/t/lumen-rendering-latency-refresh-rate-in-real-time/1203410/1 "2023-06-18T20:18:05Z")
Hello, Here’s my problem. I have integrated a led screen on my stage, but I have a rendering problem with lumen, the reflections don’t load quickly enough and when there are strobes or fast videos the reflections are super slow (video attached). The video signal comes from a Blackmagic capture card, I have the same problem with NDI… Maybe Lumen isn’t made for this idk ? I’m still new to unreal Do you have any ideas? Video : [Lumen reflections problem - YouTube](https://youtu.be/jAhmycCF0Iw) PC Config : I9 10900X RTX 4070 32GB RAM Many thanks ---
**Author:** ![ClockworkOcean](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/clockworkocean/32/1169999_2.png) [@ClockworkOcean](https://forums.unrealengine.com/u/ClockworkOcean)\ **Post date:** [June 19, 2023, 5:57am UTC](https://forums.unrealengine.com/t/lumen-rendering-latency-refresh-rate-in-real-time/1203410/2 "2023-06-19T05:57:15Z")
I don’t think you’ll get that working with Lumen. It needs a few frames to get the GI sorted out, and you’re just not giving a chance. Might be best to turn Lumen off for that sort of scene. ---
**Author:** ![jeffmeyer3d](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/jeffmeyer3d/32/965059_2.png) [@jeffmeyer3d](https://forums.unrealengine.com/u/jeffmeyer3d)\ **Post date:** [June 19, 2023, 4:05pm UTC](https://forums.unrealengine.com/t/lumen-rendering-latency-refresh-rate-in-real-time/1203410/3 "2023-06-19T16:05:34Z")
### Lumen Lighting Update Speed Lumen uses a number of caches to achieve real-time performance. While local lighting changes propagate quickly, global lighting changes, like disabling the Sun, can take multiple seconds to propagate. Projects can use the **Lumen Scene Lighting Update Speed** and **Final Gather Lighting Update Speed** [controls in the Post Process Volume](https://docs.unrealengine.com/5.0/en-US/lumen-global-illumination-and-reflections-in-unreal-engine#postprocesssettings) to work around this delay at the cost of increased GPU cost. ---
**Author:** ![jblackwell](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@jblackwell](https://forums.unrealengine.com/u/jblackwell)\ **Post date:** [June 19, 2023, 10:54pm UTC](https://forums.unrealengine.com/t/lumen-rendering-latency-refresh-rate-in-real-time/1203410/4 "2023-06-19T22:54:28Z")
I might recomend figuring out a way to feed that screen buffer into the source texture of a rect light covering the bounds of the screen mesh. Analytical lights can update way, way faster than lumen, and if you have RT with soft shadows you’ll get a very similar effect to lumen reflections. ---
**Author:** ![Miguel1900](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/miguel1900/32/1010694_2.png) [@Miguel1900](https://forums.unrealengine.com/u/Miguel1900)\ **Post date:** [June 21, 2023, 4:24pm UTC](https://forums.unrealengine.com/t/lumen-rendering-latency-refresh-rate-in-real-time/1203410/5 "2023-06-21T16:24:01Z")
You can disable temporal accumulation, but it won’t have enough information and would generate tons of noise, as Lumen is temporal-accumulation dependent.