As this is still confusing people here a quick check list, basically you want to avoid auto exposure and make sure that render settings match the viewport settings -
- On you camera, search for ‘‘exp’’ and change the setting to manual, then adjust the exposure using the exposure compensation.
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If it doesn’t work, try doing it in the post process volume if you have one. (It’s exactly the same there)
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If that doesn’t work, check the viewport setting -
Make sure game settings is ticked, the EV100 will give you a different exposure just for the viewport but I don’t think it affects the render.
- There’s also another setting in the project settings, make sure you untick ‘‘auto exposure’’
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If there’s still an issue, make sure you’ve not hidden any lighting in the scene by disabling it in the outliner (The light will be re-activated in the render). To properly disable a light, you should search for ‘actor hidden in game’’ and '‘visible’ in the lights details panel and adjust those settings.
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If again it’s still occurring, maybe you’ve disabled the tone curve in the render settings in the color output tab (if you’ve added it) or you’re using an OCIO config for the viewport that doesn’t match the one in the color output tab in the render settings (if you’ve added it). Viewport OCIO is set in the lit tab, shown at the bottom of the window by OCIO Display as seen in one of the above images.
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Another possible cause is the use of more than one directional light in the scene, if forward shading isn’t set correctly, then the engine will chose one over the other for lighting volumetric fog etc, and this could differ when the engine loads for rendering.
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Also check in your render settings that you’re actually rendering the correct level, this can happen if you have duplicate levels with different lighting and you haven’t set up the sequencer to correctly match the level you want to render. I made a more detailed post on this here - Transfering sequencer and cameras to another project - #2 by Origenic
These are all the possible causes I can think of at this moment but there maybe more.