Moving a point on a curve left or right?

[media kat]

When you place points along the curve and raise them it is making those points brighter, and if you lower the points it is making them darker. What is happening if you move a point to the left or the right? If I place a point at the mid point on the curve and go left or right with it, what is it technically doing to the tones of the curve and the image?

[D Fosse]

Well, you can see how the curve looks, right? Also read input>output values for each point.

[ricardogsouza]

Up and down you'll change de output value of that point.
Left and right ll'be the input value.

basicly, when your move up and down you change the the lighten and darkens of that point.
Left and right you'll increase the contrast.

[D Fosse]

It's simpler than that: a steeper curve increases contrast. A shallower curve reduces contrast.

If the endpoints remain fixed, that means more contrast in parts of the tonal range, and less in others. A standard S-curve increases midtone contrast, but reduces shadow and highlight contrast.

[media kat]

I understand that going up and down is brightening or darkening the point when in the RGB channel, and adding/removing color when in the individual channels, but what does it mean to add contrast? By pulling up or down on different points on the RGB curve, isn't that adding/removing contrast? Isn't that what the S-Curve is? I'm confused by moving a point left/right.

Thanks for your patience.

[Theresa J]

Moving a point on the curve above, or to the left of the diagonal starting point will lighten the image. Moving it the right or below will darken it.

An S curve is drawn when you move the lighter tones (top of curve) to the left and the darker tones (bottom of curve) to the right. So the lighter tones become brighter and the darker tones get darker. That creates contrast.

[mglush]

Hi!

It's not just abut going up or down. By adding a point and moving the line in any direction you are shifting values. Shifting a point to the left will make the curve steeper and increases the highlights (see below)

This is Max at a Normal setting with no Curves adjustment

This one I have moved the point to the left and made the curve steeper. By doing this my white point and black point stay the same but where the curve changes it pushes the values so the mid tones are brighter.

By moving the point to the right the curve is flatter and it pushes the mid tones darker.

When you have a very flat image -- the pixel values will be centered in the dialog box-- and there is no information in the blacks or whites part of the histogram that you see behind the line -- everything is sort of gray and muted. See below

That is when you want to add contrast and use an S-curve. An S-curve deepens the shadows and brightens the highlights. See below

Changing the Curve isn't necessarily for changing the color. It's about changing the value -- the brightness and darkness of a pixel. Colors do shift when changing the lightness and darkness values but that is a side effect.

I hope that helps! Let us know if you have any questions!

We're here to help!

Michelle