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Luminance control actor



  • hi everybody!

    I havent found an actor which controls only the luminance of a video string.
    the hsl adjust actor controls luminance, hue, and saturation, but as far as I understand it also
    consums a lot of resources from the computer.
    does anybody has an idea how to control luminance with a simpler actor, or has developed
    his/her own luminance control actor?
    thanks!!!!!

  • Tech Staff

    What is wrong with the normal Luminance Key Actor? Is this what you mean? d9a061-screen-shot-2013-01-26-at-10.15.29.png



  • skulpture.

    before everything I want to excuse myself, since I pledge ignorance. it is very probable that what I want is very easy to get.
    the luminance control in the hsl adjust actor, is a sort of opacity control, which allows you either to see or not to see the video string you are processing.
    I have tried to do this with the luminance key, mixing it with "nothing" (which would be black) but I see much more complex results. 
    am I doing something wrong?
    thanks!


  • Hi,

    Did you played with the video fader actor and with the intensity input of the projector ?
    Best
    Mehdi

  • Tech Staff

    Don't apologise we run a very open forum here. Even the pros ask basic questions now and again ;-) It sounds like good old Mehdi has answered your question, let us know how toy get on. Often a screen shot of your patch helps us figure out what you trying to achieve.



  • And note that if you do your "fade" with the intensity input of the projector, it will be openGL ( so GPU ) based, so the best performance solution.



  • There is also the Contrast Adjust actor. But try keftparty's idea first.

    Best Wishes,
    Mark


  • hi!

    thanks everybody. its a beautifull forum.
    contrast adjust is not what I need. I have already been using it for other porpouses anyway. thanks mark!
    video fader actor is perfect. 
    skulpture, thanks too!
    leo.-
    I am anxiously waiting core video upgrade for windows!


  • Is the operation in the Luminance portion of the HSL actor identical to adjusting one of the parameters of the Contrast Actor (out max)?  I'm wondering about also the situation where one increases Luminance above 100, making bright values brighter.

    Is there any relation between luminance in the HSL actor, and the definition of luminance that includes perceptually weighted values for R, G, and B?
    I am partly asking in order to determine how to accurately reproduce the look of increased brightness applied by HSL in an After Effects or Photoshop edit for those situations where one needs to improve performance of a scene by "burning in" the adjustments to the content once they are set.
    best,
    David


  • Hi David,

    The hsl adjust actor is pretty heavy in terms of cpu process.
    The result that you describe makes me thinking that you can maybe get it by sending your signal to two ( or more ) projectors, setted on additive blend mode ( see screenshot ).

    Using the projector, your "effect" is done on the GPU.
    Best
    Mehdi

    f36e9c-screenshot-isadora-2-layers-additive.jpg



  • Thanks Mehdi,

    This multiple projectors solution is in fact something that I do a lot to get that effect.  
    I recently found, however, that I wanted to recreate not just a luminance adjustment, but saturation and hue shift as well, in pre-rendered video.   Levels adjustments seem to get close to the behavior of Izzy HSL luminance adjust, but I'm wondering what the actual operation is to get it exactly :-)
    This is also partly a question of just curiosity about how the luminance adjust is defined in HSL adjust.
    best,
    David

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