curves

Hello.

I have used Curves to adjust color & contrast / brightness in both Pshop and PSP.

I have never really understood the difference between (say, when you're adjusting the RED component curve), when you want to decrease the amount of RED in a photo, of pulling down the end-point in the upper right corner of the graph, or, say, clicking in the center of the line to establish a mid-way point, then pulling down the mid-point slightly to decrease the amount of red.

both of these moves seem to have a similar effect.

can this be explained in "layman's terms" without being too technical?

thanks for any input..

Santa

santa

If you pull down the midpoint, pure white remains at RGB(255,255,255), and the midrange red values will be decreased. This is a reasonable operation that would be used to get rid of a cyan cast in the midtones, when you

Pulling down the red midpoint removes a cyan cast? I can't see the logic behind that. Can you explain?

"Derek Fountain" wrote in message

If you pull down the midpoint, pure white remains at RGB(255,255,255), and
the midrange red values will be decreased. This is a reasonable operation that would be used to get rid of a cyan cast in the midtones, when you

Pulling down the red midpoint removes a cyan cast? I can't see the logic behind that. Can you explain?

Depends on whether your Curves dialogue is set black>white or white>black This action would INCREASE the cyan cast if your dialogue is set the other way from Mike's. Click the double-headed arrow to reverse it.

John Rampling wrote:

"Derek Fountain" wrote in message

If you pull down the midpoint, pure white remains at
RGB(255,255,255), and
the midrange red values will be decreased. This is a reasonable operation that would be used to get rid of a cyan cast in the midtones, when you

Pulling down the red midpoint removes a cyan cast? I can't see the logic behind that. Can you explain?

Depends on whether your Curves dialogue is set black>white or white>black This action would INCREASE the cyan cast if your dialogue is set the other way from Mike's. Click the double-headed arrow to reverse it.

Much as I would like to accept John's kind defense of my mistake, Derek is correct in questioning the logic of what I said. I had it backwards.

With the curves oriented with white on the right, as originally described by santac, dragging down the middle of the red curve will get rid of a red cast (not cyan), and darken the image slightly.
--

Mike Russell
www.curvemeister.com
www.geigy.2y.net

Hi Mike,

<< I've written a fun article discussing different "curve moves", and some of their common uses >>

Thanks for the article on curves.

Best,

Conrad

Conrad Weiler
Camp Sherman, Oregon