Adobe Photoshop Process Manual:

Creating a Good Tone CurveBy:

Robert BonfanteKyle Gamble

David NaChristina Oh

AudienceThis process is intended for anyone

interested in using the Curves feature of Adobe Photoshop to adjust the brightness, contrast, or color balance of an image, all in one tool.

OverviewThere are 5 steps involved in using

Curves to create a good image. These steps are:

I. Setting up the correctionII. Finding the highlight and shadowIII. Setting the highlight and shadowIV. Adjusting the midtoneV. Finding a neutral

I. Setting up the Correction1. Select the Eyedropper tool; on the Options bar, change the

sample size to 3 By 3 Average in the Sample size dropdown list. This setting gives you more accurate readings.

2. If the Histogram palette isn’t visible, choose WindowHistogram.

3. If the Info palette isn’t visible, choose WindowInfo. The info palette will show you the color values.

4. Make sure that your color settings are correct. In Photoshop, it shows you the color mode at the top of the image. You want the setting to be RGB. If it isn’t choose ImageModeRGB.

II. & III. Finding and Setting the Highlight and Shadow1. Choose WindowLayer (if

the Layers palette isn’t open).

2. Click and hold on the Create New Fill or Adjustment Layer button at the bottom of the Layers palette and select Curves, as shown in Figure 1.

Figure 1

II. & III. Finding and Setting the Highlight and Shadow cont’d2. cont’d The Curves palette,

shown in Figure 2, appears. Notice the histogram in the background. The histogram is a helpful

guide as you make corrections. Check

the Preview check box to see your changes.

Figure 2

II. & III. Finding and Setting the Highlight and Shadow cont’d3. To help you see the highlights and shadows in the

image, check the Show Clipping check box.

4. Grab the right modify curve slider (the white triangle on the bottom right corner of the Curve window), and slide it until you start to see white appear. When you click on the curve slider, the entire picture goes black. As you move the slider to the left, flecks of color will appear. When you start to see white dots, stop. It is worth noting that the white should appear at the point where the histogram slopes upward.

II. & III. Finding and Setting the Highlight and Shadow cont’d

5. Grab the left modify curve slider and drag it until you see the darker part of the image appear. Clicking on the slider will make your picture white, and as you move the slider right, the shadows first appear, and then darken. Stop when you see black flecks and then uncheck the Show Clipping box.

IV. Adjust the Midtone

1. In the Curves dialog box, click the middle of the curve ramp (the line that runs diagonally across the box) to create an anchor point; drag up slightly. The image will lighten. Do not move a dramatic amount and pay attention to your Histogram palette. In the Histogram, the bars will spread out, which is acceptable to a point.

Photographers often talk about “opening up the midtones.” This phrase basically means that you are lightening the midtone values of an image (Smith 435). Opening up the midtones adds contrast and detail to your picture.

Here are the steps to adjusting the midtones:

IV. Adjust the Midtone cont’d

2. To adjust the three-quarter tones (the shades around 75%); click halfway between the bottom of the curve ramp and the midpoint to set an anchor point. Use the grid in the Curves dialog box to find it easily.

3. Adjust the three-quarter area of the tone curve up or down to create contrast. For more contrast, pull the point downward. You want something similar to a mild S-curve. Keep an eye on the Histogram palette!

3. If you are working on a grayscale image, your tonal correction is done and you can click OK. If you are working on color, move on to the final step.

V. Finding the Neutral This last step only applies to a color image. To understand this final step, you need to know that equal amounts of color creates gray. By moving the mouse cursor over gray areas and reading the numbers in the Info palette, you can determine the colors you need to adjust (Smith 436).

1. With your Curves dialog box open, position so you can see the Info palette. If the Info palette is buried under another palette or dialog box, choose WindowInfo to bring it out front.

V. Finding the Neutral cont’d

2.   Position your cursor over your image and, in the Info palette, look for the RGB values in the upper left section. You will see color values and then forward slashes and more color values. The numbers before the slash are the values in the image before you opened Curves; the numbers after the slash are the values after the changes you have made in the Curves dialog box. Focus on the values after the slashes.

3. Position the cursor over something gray in your image. It can be a shadow or a road or building—anything that is a shade of gray. Look at the Info palette. If your image is perfectly color balanced, the RGB values after the forward slashes should all be the same.

V. Finding the Neutral cont’d

4. If your color isn’t balanced, click the Set Gray Point Eyedropper in the Curves dialog box and click on the neutral or gray area of the image. Using Set Gray Point is an easy way to balance the colors.

5. Now you can click OK; if asked whether you want to save your color target values, click yes.

Conclusion This is an easy workflow to follow but it

takes some practice to get used to. Once you get familiar with Curves, you can experiment with some of its other features. A good follow-up to Curves is the Unsharp Mask filter which can sharpen a blurry image.

There are many different ways to color correct an image through Photoshop. While Curves might be the most complex, it is also the most versatile and complete method.