Disable autoexpousure and eye adaptation

Development Rendering
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1

It looks like it is not possible to fully disable auto exposure. I tried to create an empty level with a box for ground and a small “house“ made from basic cubes. I added a DirectionalLight and player start. There are no post process volumes in the level. The directional light is set to realistic sun values of 80000lux. I’m using Unreal Engine 5.6.1

In the first person camera component in player character, i set exposure “Metering mode” to manual, “apply physical camera exposure“ checked, “Exposure compensation“ to 0, “Min/Max EV100“ to 0.

Global illumination method is lumen, reflections are also lumen.

Now the scene brightness relies on fstop, shutter speed and iso.

When i change, for example ISO from 100→50000 the scene goes completely bright, however, after a second, it gets more gray, and becomes better visible.

When i change, for example ISO from 50000→100 the scene goes completely black, however, after a second, it gets more gray, and again, becomes better visible.

If i understand manual exposure correctly, this shouldn’t be the case. There should be no dark/bright blending over time. When i set ISO, fstop or shutter speed, the scene shouldn’t blend to the correct exposure but should immediately jump to it, without any additional change over time.

Are there any other setting i have to apply to the camera to completely disable eye adaptation / auto exposure? Is this intended behavior?

Is this auto-exposure behavior or is it related to other things like tone mapper or something similar?

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It’s a bit confusing, you need the fix the player camera for runtime, but you also need a PP volume in the level while you’re editing it.

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That’s the problem, even if these settings are overridden in project settings, camera settings and post process settings, the exposure effect is still there. Also, i have this problem in game, i’m not testing it in editor.

I have this problem in PIE and standalone game.

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Whatever it is you are seeing is probably not auto-exposure if you’ve done all of this

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Thank you for the response, after some testing it looks like this may be the case.
The problem only happens when i use Lumen for Global illumination and reflections.

When i change “Global illumination“ → “Method“ from Lumen to none and “Reflections” → “Method“ from Lumen to none; the exposure problem disappears, and exposure works as intended.

So this raises the question: How should i setup Lumen to prevent this exposure effect?

I will do some testing tomorrow, if i find a solution i will post it here.

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It’s really hard to help without seeing what you are seeing. People tend to mistake Lumen’s slow update speed as exposure, could also be that you’re missing surface cache in the scene…

In the viewmodes seettings there are Lumen debug views that will help you identify problems

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