Locking HDR Exposure

[danni.coy]

we do a lot of capturing from the engine. Sometimes we would like to lock the exposure settings while capturing an animation, This is quite different to turning HDR off. What would be the best strategy for doing this?

 

I am something similar to using the exposure lock button on a real camera.

[frustum]

we do a lot of capturing from the engine. Sometimes we would like to lock the exposure settings while capturing an animation, This is quite different to turning HDR off. What would be the best strategy for doing this?

 

I am something similar to using the exposure lock button on a real camera.

 

Use min/max luminance parameters in render.

[danni.coy]

Use min/max luminance parameters in render.

 

So if I set the Min and Max Parameters to 0 then this will work?

What is the relationship between the HDR value and the min and max value?

 

Also I would like to have some info on how materials affect exposure. We are having issues with the sky getting dull and muddy when light coloured objects are in the foreground.

[danni.coy]

So coming from a photography background does HDR work with the assumption that the main object in the scene is 18% grey?

Is there a way to model exposure compensation (is that what setting the HDR exposure value does & is there an easy way to translate that to stops mentally)?

When exposure of the scene is calculated is it uniform across the whole scene or is it weighted in some way?

[manguste]

So if I set the Min and Max Parameters to 0 then this will work?

Not necessarily 0. It could be any value equal for both Min and Max parameters. That would strictly lock the exposure.

 

Also I would like to have some info on how materials affect exposure. We are having issues with the sky getting dull and muddy when light coloured objects are in the foreground.

...

Is there a way to model exposure compensation

HDR postprocess is about adaptive exposure, so it compensates the exposure basing on the average luminance of the current screen image. Naturally, the lighter the material and the more space in the viewport it takes, the shorter (lower) the exposure.

 

You can find the detailed description (how exactly HDR is calculated and what are the exposure, min/max luminance values) here: Principles of Operation -> Rendering Sequence -> Postprocessing. You may also find usefull the following section of the tutorial: Tutorials -> Adding Sun, Sky and Clouds -> Step 4. Setup HDR.

 

BTW, if the result still does not appear satisfactory, try switching between logarithmic or quadratic HDR (render_hdr 1 or render_hdr 2 followed by render_restart command).