Curves vs Levels

CPestoCPesto Website User Posts: 45

I typically use curves to adjust things in my image/video but I was watching a tutorial and the instructor used levels almost exclusively ( he was teaming fire). 

How does one decide  to use one over another?  

Comments

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,217 Ambassador

    Personal choice, and what are you doing? Levels is a simpler control than Curves and adjusts only the black and white points while leaving a pure linear interpretation between values. Curves allows full control of the midtone values and interpolation between points. 

    Try this. Apply a Curves filter, then adjust the existing black and white points horizontally (so sliding the white point left and the black point right). This is exactly what Levels does. 

    Now reset Curves and create a point halfway up. Move this point left and right... That's what the Gamma filter does--move the midpoint of a channel. 

     

  • NormanPCNNormanPCN Website User Posts: 3,945 Enthusiast

    In Hitfilm the levels histogram effect has a pretty stiff performance penalty relative to curves. It may not matter in a given situation but it is there.

  • CPestoCPesto Website User Posts: 45

    Thank you both for the explanation. 

    Triem23 - I am compositing fire into a scene. I was watching a tutorial by Mark Christiansen and he was using Levels. I tried to create the same thing using Curves and came very close. The way you explained the curves filter was very helpful, thanks again!

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,217 Ambassador

    @NormanPCN probably because of the built-in histogram. 

    CPesto glad it was a helpful description. :) 

  • NormanPCNNormanPCN Website User Posts: 3,945 Enthusiast

     @Triem23 "histogram".

    That is my assumption. I do see a bump in CPU use with levels. Probably the histo code. This would also likely bring in a GPU readback of some kind. That hurts in Hitfilm.

    What irks me is why we get the same overhead (performance loss) when the histogram is not visible. If I can't see it then why do the work to update it. It's just a simple boolean. Do/update histogram, TRUE or FALSE.

    Since histo has overhead then why don't we have a check option to enable/disable histo update during playback. Again a simple boolean.

    ...

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,217 Ambassador

    @NormanPCN one for the wishlist. :) 

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