A Photoshop tutorial for photographers

everal years ago we sold our darkroom equipment and moved our image editing to the computer. The image editing software we chose was

Adobe Photoshop. It took us about a year to be able to make images from the computer that were as good as ones we had made in our wet darkroom.

Today we are making images that we could not even have dreamed of making before. Since then our expertise in Photoshop has increased many times over, and we continue to refine our workflow.

This tutorial is based on Photoshop version 6 for Windows.

The following is the basic workflow we use to prepare our images.

1. Levels Adjustment to correct exposure and color cast

2. Hue/Saturation adjustment to correct overall saturation and saturation of specific colors

3. Removing dust and scratches

4. Sizing the image for output

5. Sharpening the image

Image Correction
USING an ADJUSTMENT LAYER

Although tools like Levels and Hue/Saturation can be applied directly to an image layer, Photoshop offers another more flexible means called adjustment layers. An adjustment layer differs from an image layer in that the adjustment layer does not contain any pixels. It does include instructions on how the image layers below it will be affected. An adjustment layer can also contain a mask, which limits the areas of the image that will be affected. Using an adjustment layer has the advantage that you can come back at any time and make changes, even after the image has been closed and reopened. By using adjustment layers your original image is left unchanged. In this tutorial the use of the Levels and a Hue/Saturation adjustment layers will be shown. They make up the basis of image, color correcting in Photoshop.

Levels Adjustment

With your image open in Photoshop click on the “create new adjustment layer” icon (figure 1) at the bottom of the layers palette. Select “Levels” from the pop up list (figure 2). A Levels dialogue box will appear and a Levels layer will appear above your background image (figure 3). Drag the box by its title bar so that you can see both the image and the dialogue box.

The graph called a histogram is a visual representation of the tonal range of the image. The black triangle (1) on the far left represents pure black, no visible details. This triangle is referred to as the shadow levels slider. The hollow triangle to the far right (3) represents pure white, no visible details. This triangle is called the highlight levels slider. The gray triangle in the middle (2) adjusts the contrast and is called the midtones level slider. The two sliders at the bottom represent the Output Levels and will not be used at this time.

Figure 4

Figure 5

Color Cast Correction

Look at the image on the screen to determine if it has a colorcast. If it does not, you’re done with this step, click ok. If there is a colorcast click on the drop down at the top of the box and click on the Red, Blue, or Green Channel (figure 7). Choose the color channel based on the following:

• Red Channel for correcting red or its opposite color cyan

• Blue Channel for correcting blue or its opposite yellow

• Green Channel for correcting green or its opposite magenta

Adjusting overall saturation

In the drop down list at the top of the box Master should be selected (figure 9). There are three sliders, Hue, Saturation, and Lightness. If these names are new to you, think in terms of your color television, hue is tint, saturation is color, and lightness is brightness. The Saturation control is the one we are interested here.

Drag the Saturation slider to the right to increase saturation, and to the left to decrease saturation. Adjust to where the image as a whole looks best. None of the colors should look overdone.

Exposure Correction

Take a look at the histogram, although there is not a definitive way a histogram should look, a typical image should have a tonal range that extends from pure black to pure white. If the histogram does not extend to the endpoints, the image does not contain the maximum tonal range.

Always try the Auto Button first (figure 4). This will take the highlight and shadow triangle on each color channel and move them to the end points on the histogram where the information begins. This is not a fix all button but it can work as a starting point. If you don’t like the results click Ctrl + Z or hold down the Alt key and click on the resulting reset button in the dialogue box (figure 5). By holding down the Alt key the Cancel button becomes the Reset button.

Figure 2

To make the adjustments manually use the mouse to drag the shadows level slider to the left hand side of the histogram. Drag the highlight levels slider so that it is at the right endpoint of the histogram. Now take the midtones levels slider and adjust left to right until you have the desired look. Continue to tweak the sliders until you are satisfied (figure 6).

Figure 6

Figure 1

Figure 7

Drag the midtone slider to the left to increase the Channel color, or drag it to the right to decrease the Channel color and increase its opposite color. For example if the image has a green cast, go to the Green Channel and drag the midtone levels slider to the right. If the image has a yellow cast go to the Blue Channel and drag the midtones levels slider to the left.

As a rule of thumb try to remove the offending color cast rather than try to cover it up by adding other colors. If you are new to color correcting experiment with the Color Channels and midtone levels slider while watching the results of your adjustments on your image. You can reset all the settings and start over by simply holding down the Alt key on the keyboard and clicking on the resulting “reset” button.

To summarize when the Levels box is first opened the RGB Channel is active. Adjust the tonal range of the image by use of the shadow levels slider, and the highlight levels slider. Adjust the contrast by use of the midtone levels slider. To remove a color cast use one of the individual Red, Blue, or Green Color Channels and adjust using the midtone levels slider. When you are satisfied with the results click ok.

The layers palette now has two layers, the original image and a Levels adjustment layer.

Enhancing Color
Using a Hue Saturation Adjustment layer

As you did earlier, click on the make new adjustment layer icon at the bottom of the layers palette. Choose Hue Saturation from the list (figure 8). Click on the title bar of the dialogue box and arrange your screen so you can see both the image and the Hue Saturation box.

After Levels Adjustment

Figure 8

Figure 9

Adjusting saturation of specific colors

To adjust just one color without affecting the other colors go to the Edit drop down list and select the particular color you want (figure 10). Notice that unlike the Levels box, you know can choose from red, blue, green, and cyan, magenta and yellow. Choose the color you wish to adjust. Use the Saturation slider to adjust the intensity of the color, the Hue to change the color, and the Lightness to change the density of the color.

The three little eyedroppers are to help define the exact colors you want to adjust. Select the left eyedropper by clicking it once. Now click in the image on the color you want to select. You can only click once, if you click more than once only the last color clicked on will be active. The middle eyedropper with the plus sign is used to add to you color selection. This eyedropper can be used multiple times, each time adding to the color selection. The third eyedropper, the one to the far right with the minus sign is to subtract from the selection. It too can be used multiple times.

When saturating individual colors care must be taken such that the colors don’t look disjointed from the image. The sliders on the color bars help with this. The inside brackets determine the color spectrum range, and the outside ones determine the blend to the other colors.

Figure 10

Summary for enhancing color

The Hue/Saturation almost seems like magic with its ability to increase color saturation independent of image lightness. This trick is all but impossible with traditional wet darkroom processing. By using it as an adjustment layer we are free to go back and tweak it at any time.

The before and after images below show the dramatic difference Hue/Saturation can make.

When you’re satisfied, click ok to close the dialogue box.

Size the image
Pixel dimensions verses document size

Images from digital cameras and scanners are sized in pixels not inches. When the computer opens the image it sizes the document by assigning one pixel in the image to one pixel on the monitor. Before outputting your image the document size must be set.

On the Photoshop toolbar click “Image” then click Image Size (figure 11). The image size dialogue box opens. First, the “Constrain Proportions” should be checked (figure 12).

If you are going to print the image the “Resample Image” checkbox should be left unchecked. Go to document size, select inches for the unit of measure and enter a value for the “with” of your print. Notice that the height changes automatically because the “Constrain Proportions” is checked. The pixel dimensions should not change because the “Resample Image” was not checked.

If you are going to output the image to the web, check the “Resample Image” checkbox. The resolution should be set to 72 pixels/inch. Set the document size as desired. Note, the small images on our web site are 2 x 3 inches and our large images are 4 x 6 inches at a resolution of 72 DPI. When resizing images for the web I suggest that you first make a copy of your image and save the original full resolution file. To make a copy click on “File”, then “Save As”. Give it a different name than you web image file, so that one won’t overwrite the other.

Before Hue/Saturation

After Hue/Saturation

Figure 11

Figure 12