Cooler Curves Come to Photoshop CS3
I like Curves. They provide a tremendous degree of control when making adjustments to both tone and color in an image. But as useful as they have been up to now, Adobe has made Curves even better in Photoshop CS3.
Everything that Curves used to do it still does, so you should feel right at home if you are used to prior versions of Photoshop. But Adobe has thoughtfully added a number of new features that users have been asking for for years.
When you first open the Curves dialog in Photoshop CS3, you will likely notice one of the major differences right away: there's now a histogram superimposed on the same grid used to graph the Curve. Given that the Levels has had a histogram forever it's about time that Curves finally does. Thank you, Adobe.
There's also now a Show Clipping checkbox to switch the image being adjusted to a clipping display. Rather than requiring the use of the Alt (Option) key as does the equivalent feature in Levels, the Curves clipping display automatically toggles between showing you shadow clipping and highlight clipping based on which end of the Curve you are working on. Click on the dot for the black point at the lower left end of the Curve and you'll get a shadow clipping display with everything in the image turning white except where the shadows are being clipped in at least one channel. Click on the upper right hand dot at the white point end of the Curve and you'll get a highlight clipping display with the entire image going black except where you've blown out the highlights in at least one channel. By sliding the corresponding end point left or right along the edge of the grid you can now set the white and black points in Curves with the same accuracy as used to be possible only in Levels. Another big thank to Adobe. I would expect a similar checkbox to be added to Levels in the next release of Photoshop to do away with the Alt (Option on Mac OS) keystroke needed the old way.
But that's not all that's been added to Curves in CS3. By clicking on the Curve Display Options button at the bottom of the default dialog you can expand the window to include a number of other useful options.
The first of these new options is a toggle to let you select whether you want the Curve based on the amount of Light (0-255) or the amount of Pigment/Ink % across the image. Normally, when working in RGB mode you'll want the former, and for CMYK work the latter. When you switch to the pigment mode, the grid axes will flip and show you white on the bottom left and black at the top right. As you move up the Curve, ink density increases since the more ink you add to a page the darker the color gets. The clipping display mode is disabled when working in pigment mode.
Curves in prior versions of Photoshop used to require you to click on a somewhat hidden button in the middle of the bottom axis to switch between light and pigment display modes. This happened by accident for many users when the clicked on this button unintentionally. All of the sudden Curves would go crazy and they often wouldn't know what they had done to cause it. Now if you change modes you'll at least be able to see how you did it so you can switch back.
A pair of toggle icons to the right of the light versus pigment choice allows you to switch between four and ten grid lines along each axis, breaking the tic-tac-toe grid up into larger or smaller squares. In older versions of Photoshop this was done by Control-clicking (Comand-clicking on Mac OS) in the grid area with your mouse. No more hidden options.
There are also four checkbox options for turning on display of various Curves dialog features.
Channel Overlays enables turns on the display of the individual channel curves (red, green and blue in RGB mode). Yes, you can see them all at the same time, on the same grid now. And by the way, when you edit the curve for a single channel, it displays in the correct color rather than monochrome as previous versions of Photoshop did.
Baseline turns on the display of the original unmodified curve line overlaying your modified curve so you'll know where you've been, not just where you are going to.
Histogram turns on the display of the superimposed histogram. Now that you've got it, I'm not sure why you'd want to turn this off, but un-checking this box will do so if you want.
Intersection Line enables you to see the horizontal and vertical intersection lines showing you where the point you are adjusting is on each axis. Since you get both horizontal and vertical lines, this ought to be called "Intersection Lines" (plural) rather than just "Line" (singular), but perhaps Adobe will get the grammar correct in the next release.
This is a long overdue upgrade to the Curves dialog. Thank you, Adobe. Did I mention that already?