exposure adjustment vs. curves

2012-12-31
2013-02-27
  • Gary Aitken
    Gary Aitken
    2012-12-31

    Can someone explain to me if there is a difference between adjusting exposure via the main exposure control slider, and adjusting it via a curve (Under "Base curve" tab or under "Correct luminosity, saturation" tab)?  When I have a large dynamic range, I have tried to use the curves but can't seem to get the increased definition in the shadows that I can get by adjusting exposure, but then that blows the hilights.  Maybe I have to use an hdr approach with two images, but before doing that I would like to understand what the two controls do a little better.  Thanks.

     
  • The exposure slider gives the same adjustment to the whole image. You can shape the base curve to give more adjustment to e.g. the shadows or the highlights. Often you will use a combination of both.

    Have you read the user guide? It is here: http://ufraw.sourceforge.net/Guide.html

    Regards,
    Niels Kristian

     
  • Gary Aitken
    Gary Aitken
    2013-01-01

    I thought I had :-)  But it wasn't clear to me that it was the same adjustment exactly.
    Thanks

     
  • Gary Aitken
    Gary Aitken
    2013-01-04

    On thinking about this a little further, I still have a question…
    What exactly does "gives the same adjustment to the whole image" mean?
    Does it just shift the linear curve to the NW or SE, and clip correspondingly both highlights and shadows? 
    It doesn't seem like it does that.
    If it doesn't do that, it must curve the default straight line somehow.
    It would be helpful if there was a way to view the curve as a result of what the exposure changes do, so one can make more reasonable adjustments subsequently; or at least understand exactly what the exposure change does.
    This is one of those cases where a picture's probably worth at least a few hundred words, at least for the user's guide.

     
  • The best analogy of the exposure slider is moving the linear curve up (making the whole image brighter) or down (making the whole image darker) just like the exposure compensation on a camera.

    Regards,
    Niels Kristian