More on Hue/Saturation in Photoshop
Last week, I wrote about adjusting saturation in Photoshop using the Hue/Saturation tool. Given the importance of color, it's no wonder I wasn't able to cover everything. So this week I'm picking up where we left off. I mainly covered the middle of three sliders, the Saturation adjustment. I don't feel too bad though for neglecting the other two sliders in Hue/Saturation since even Adobe only mentions two in the name of this dialog. For the record, Adobe should have called it Hue/Saturation/Lightness since the other two sliders are Hue and Lightness.
Together with Saturation, these three variables can describe any given color using the HSL, or Hue/Saturation/Lightness color model. Hue specifies the gradation of color around the traditional color wheel. By moving the slider left or right, we can shift colors to become different colors. Lightness describes how bright or dark a color is so we can make colors closer to black on the left or white on the right-hand end of the slider.
As with Saturation, Hue and Lightness can act on all colors equally if you select the Master channel from the Edit dropdown list at the top of the dialog. Also like Saturation, you can work on just a range of colors by selecting one of the other channels from that same dropdown list.
If you want even more control over which colors get selected, you're in for a treat as Adobe provided plenty of ways to fine tune your color selection.
You may have noticed the two colored strips at the bottom of the Hue/Saturation dialog. The way the bottom strip lines up with the top shows you what changes you are making to source colors in your image. To begin with, both strips show you the same colors, but as you make adjustments with the sliders, the colors in the bottom row will change. Each source color in the top row is getting mapped to each target color in the bottom row. For instance, if you select the Master Edit channel and pull the Lightness slider all the way left, the image will turn completely black along with the bottom color strip. If instead you adjust the Hue slider one direction or the other, again with the Master channel active, the bottom color strip will shift relative to the top. You can think of the color strips as wrapping around from one end to the other to form a flattened version of a color wheel.
If you pick a channel other than Master, some additional markings will appear between the two color strips. Colors between the two innermost markings that look like vertical bars are completely selected and those lying from them out to the two triangular markers are partially selected in order to feather the color range and blend your changes into the rest of the image. The Cyan channel lives at the very ends of source color strip where the two ends logically join together to complete the color wheel. The selection markings between the color strips will seem somewhat out of order if you select Cyan with two at one end, and two at the other end with a huge gap in between. Think of the colors as wrapping around, end to end though and the Cyan markings should make more sense.
After picking a channel, if you want to fine tune the colors you have selected, you can drag all four marks around to suit your needs. Move the triangle marks further out to feather the selection more, or pull them in tight against the vertical bars to make a more abrupt transition. Move the bars themselves in or out to adjust the width of the color range.
If you want to dispense completely with the Edit dropdown channel list, you can select the color range using the eyedropper tools instead.
There are three eyedroppers. If you click with the first one on a color in the image, colors near that color will get selected. Photoshop will give your new selection a name in the Edit dropdown if it doesn't match up with one of the predefined entries. To select a wider range of colors, click and drag through the image with this same eyedropper.
The second eyedropper lets you add colors to an existing selection. Clicking on a new color in the image will widen your range to encompass the newly selected color as well as the existing ones. You can't make a selection that isn't contiguous. The third eyedropper will shrink the selected range to remove the colors you click on. As with the main eyedropper, you can also click and drag to add or subtract multiple colors at the same time. And again, Photoshop won't let you create any gaps in the range so some colors you don't click on may end up needing to be removed to get rid of the ones you do click on. If you're a keyboard fan, you can make the main eyedropper work like the other two by holding down the shift key while clicking with it to add, or the alt/option key to subtract.
Unlike with the lasso and other selection tools, there's no visual indication in the image itself to let you know what portions you have selected. As a convenient trick to help you tell, temporarily make an extreme adjustment such as pulling the saturation slider all the way to the right. This will result in a rather ugly image, but will make the affected colors stand out more prominently. After moving around the vertical bars and triangle markings to get just the color range you want, simply put the saturation slider back where you really want it.
As mentioned last week, be careful not to overdo your changes. When moving the Hue slider for instance, watch the colors in the bottom color strip. With small changes in Hue, you will effectively be shrinking the selected portion of the spectrum while stretching the portion in the feathered transition zone next to it. Move the Hue slider too far though and you will pull colors beyond the triangle mark on that side into the selected range and create a color inversion. Not good.
If you get a set of adjustments in Hue/Saturation that you really like, you can save them for future use by clicking on "Save" or use "Load" to reload a previously saved settings file.
There's also a Colorize checkbox in the lower left that isn't very useful for normal image optimization but does work great for creating sepia toned or other colorized black and white versions of an image.
Many images will benefit from at least some tweaking with Hue/Saturation (on an adjustment layer of course). Think of it as the digital equivalent of the traditional Enhancing filter, but with the added bonus capability of visually modifying the effect to meet your needs after the fact. Ah, the joys of digital photography.