Adobe Photoshop 7 Basics II

Adobe Photoshop 7 Color Basics II

Motivation: Demo HSL & Curves color correction features of Adobe PhotoShop 7

The first tutorial showed how to use Photoshop's Levels tools to make under or overexposure color corrections. We saw that the intensity spectrum or histogram showed b y its shifts which way the image was off and so suggested the color corrections. In this tutorial we don't have any guiding indicator, and have to use our innate sense of color to correct for saturation and brightness.


The before image	The after image

The second most often used tool in color corrections is for HSL=hue-saturation-lightness. The need is for images that are are desaturated, lifeless in color. HSL can really pick up the colors of an image. However, the tool most often used incorrectly is also by HSL. The reason is that users try to use the Hue property for color balance correction or the Lightness property for brightness and contrast corrections inappropriately. The simple matter is that HSL is only effective for minor shifts in color and lightness because unlike the Levels and Curves color correction tools, HSL moves/shifts hues/lightness linearly while the former tools do so proportionately. Bottom line - use HSL for small color shifts. Too much HSL corrections can quickly go awry.

The trick in HSL (click Images | Adjustments | Hue/Saturaion menuitem) color corrections is kiss. Keep it simple and gradual in the size of the shift. Always plan to do an HSL correction along with Levels or Curves. Do the HSL first, especially in this case where the color saturation is off as here where there is a 15 point move in color saturation. Note that as the saturation is increased in double digits, lightness is lowered slightly. This

decrease offsets the natural lightening effect a greater color saturation has on the image. Then the next step will be to use the Levels or Curves tool to correct for overall image brightness. Think of our color problem as twofold. The colors are drab for which we have corrected by adding more saturation. Now we must selectively raise the brightness or intensity of the midtones but not loose the richness of the highlights. Levels can do this but it is easier with Curves because the graphics editor gets to set the exact brightness curve for the complete tonal range. Watch the Flash demo below:

Note the advantage of the Curves color correction tool - we can precisely define the curve for the corrections to lightness/intensity. And like the Levels tool we can do so for each color regardless of which color mode we are using. Users will find that once they become accustomed to the color correction tools , they will spend a large amount of time among the Levels, Curves and HSL tools.

A Word of Caution. Digital darkroom programs can do wonders correcting 1 or 2 f-stop photo mistakes. But nothing replaces good photo exposures. This is particularly true in the case of color saturation. There is not much one can do if the picture is bady underexposed and especially overexposed. If the image has does not have any colored pixels to work with - no program will be able to "inject them in".

Top of Page PhotoFinishes Home Adobe Links Adobe Books