Merge different exposures into HDR image

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Merge different exposures into HDR image


Post by AbdelrahmanMSaid » Fri Jul 13, 2018 9:17 am


Is there a way I can replicate Photoshop's feature 'Merge to HDR' inside Fusion? I have been looking online for a way to do that, or at least some simple explanation of the math behind it without a lot of success.

What that feature does, in case you haven't used it before, is that it takes multiple images with different exposures, and merges all of them into one high dynamic range photo.

Do you think there is a way of doing this in Fusion?


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Re: Merge different exposures into HDR image


Post by gez » Tue Jul 17, 2018 8:33 pm

I did some experiments using Blender's compositor not long ago with success. It should be trivial to reproduce in Fusion.
Basically I converted the RAWs from my camera to linear Tiffs using dcraw, then loaded them into the compositor, scaled and aligned exposures using multiply nodes and created luminosity masks for each bracketed exposure. Finally I blended everything together with an alpha over.
The result was pretty good, the ratios were fine and the amount of noise was greatly reduced as one would expect from stacking into HDR.

It's important to note that I didn't use jpegs or any display-referred image formats as source. I wanted them to be linear so I used RAWs.
In display-referred formats, although they can be linearized, you can never remove the camera's "secret sauce" baked in the image. You can't get scene-referred ratios from them easily, so it's always preferable to use raws as starting point.