This technique is a contrast/tone and color correction technique all in one. Once you run through it, you will see how just about any image can be improved, and you will use this technique many times over. For a number of years, this was just about the only correction technique that I used.
Step 1: The Original
Figure 1 is an image that I snapped during a trip to the amazing city of Hong Kong. As you can see, the image is lacking a bit of contrast and also has a slight colorcast to it. It’s not that bad, but it looks somewhat dirty. You will soon see a huge difference in image quality. You can download this image to work with during the tutorial, or pick an image of your own.
Step 2: Setting the black point
We are now going to set the black and white points in the Levels settings. Choose a Levels adjustment layer from Photoshop’s layers palette. In the Levels dialog box, double-click the Set Black Point tool as shown in Figure 2.
Step 3: Black point settings
You will see a color picker. Set everything to solid black and then change the setting under “B” to 5, as shown in Figure 3. This sets the black point to 95% black. Click OK.
Step 4: Setting the white point
Double-click the Set White Point tool, which is the white eyedropper. In the color picker, set for pure white and then enter 95 into the “B” setting as shown in Figure 4. The white point is now set to 95% white.
Step 5: Finding shadows
We are now ready to perform the image correction. We will click the Set Black Point tool in the darkest part of the image and the Set White Point tool in the lightest part.
To locate the darkest part of the image, hold down the Alt (Option on Mac) key, and as you move the shadow slider to the right, the image should turn white. As you move the slider you will see some areas start to show through. This is the Black Point threshold, as shown in Figure 5. The areas that start to show are the darkest areas of the image.
Step 6: Adjusting the shadows
Take note of where the dark portions of the image are on the threshold and return the slider to the far left. Choose the Set Black Point tool and click on the darkest portion of the image in the main image window as shown in Figure 6. The image will be shifted and the area we clicked on will now be set to the 95% black that we selected earlier.
Step 7: Finding highlights
Hold down the Alt (Option on Mac) key and move the right slider to the left to reveal the whitest point of the image. The image will begin as black and the highlight areas will show through as shown in Figure 7.
Step 8: Adjusting highlights
Choose the Set White Point Eyedropper tool from the Levels palette. Click on the whitest area of the image as shown in Figure 8. The lightness of the image will be adjusted to match.
Step 9: Setting the gray point
The tonal qualities of the image look much better now and the colorcast is reduced a bit. Now to totally remove the color cast. Choose the Set Gray Point eyedropper from the Levels dialog box (Figure 9). When we click on the image with this tool it will choose the selected area as the gray point of the image and balance all the color to match. Click on a portion of the image that should be a neutral gray, such as the small tower. The colors will shift; if you are not happy, keep experimenting by clicking the Set Gray Point tool in different parts of the image.
When you are happy with the result, click OK to apply the Levels to the image. You have now learned how to use the Levels tool correctly. It may seem like a lot to do, but with some practice you can perform this entire correction in under a minute. Figure 10 shows the final corrected image, a vast improvement from the original.
Colin Smith is the founder of photoshopcafe.com, a thriving Photoshop community. He is also a regular columnist for the NAPP member’s site and Planet Photoshop. He has authored and co-authored six books, including New Masters of Photoshop, Foundation Photoshop, Photoshop Most Wanted, Photoshop Trade Secrets, and Photoshop and Dreamweaver Integration. He creates video tutorials that are available at www.photoshopcd.com. When he is not writing, Colin makes his crust as a freelance graphic designer. See his portfolio at www.pixeloverload.com. This article is excerpted from Complete Photoshop CS2 For Digital Photographers (Charles River Media) and is reprinted here by permission.