DJ wrote:
> <snip>
>
> Curves. I have spent a lot of time clicking on the line and pulling up
> and down, on the left and right, not really knowing why I'm doing it.
>
> How do you use "Curves" efficiently?
>
> What reasoning is used to put a dot on the line in a specific position
> and pull the line up or down?
>
>   
I think the best thing is to play around and just see the effects you get.

As a very simple guide:

   'Values' changes the "brightness" of all three colours simultaneously
   Along the bottom of the 'Curves' graph is the "brightness" of the 
picture you took, or more accurately, its density in different parts of 
the picture, running from dark on the left to light on the right.
   The vertical scale at the left-hand side of the graph is the 
"brightness" you get by messing around with the curves - very little 
brightness at the bottom; a great deal at the top. 

Suppose the picture on your screen is much too dark in the shadows - 
then click on the curve somewhere towards the left-hand end - that is, 
where the dark tones, shadows, of your original picture lie. (It doesn't 
matter too much exactly where you click). Holding on to the dot, pull it 
upwards - in other words, you're making those shadows brighter.

Suppose the picture on your screen is burnt out in the highlights - then 
click on the curve somewhere towards the right-hand end - that is, where 
the light tones, highlights, of your original picture lie. (It doesn't 
matter too much exactly where you click). Holding on to the dot, pull it 
downwards - in other words, you're making those highlights darker.

If your shadows are too dark and your highlights are burnt out, you can 
pull up the left-hand end and pull down the right-hand end......... and 
so forth. You can produce poster effects by pulling the left-hand end 
higher than the right-hand end, etc. etc. When it all gets too much of a 
mess, press the 'Reset' button and you're back to square one.

Obviously, choosing one colour channel instead of 'Value' restricts the 
effects to a single colour.

HTH

Doug

  


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