Using the Threshold command (Photoshop)

The Threshold command converts grayscale or color images to high-contrast, black-and-white images. You can specify a certain level as a threshold. All pixels lighter than the threshold are converted to white; all pixels darker are converted to black. The Threshold command is useful for determining the lightest and darkest areas of an image.

To use the Threshold command to convert images to black and white:

1. Open the Threshold dialog box. (See Making color adjustments.)

The Threshold dialog box displays a histogram of the luminance levels of the pixels in the current selection.

2. Drag the slider below the histogram until the threshold level you want appears at the top of the dialog box, and click OK. As you drag, the image changes to reflect the new threshold setting.

To use the Threshold command to identify representative highlights and shadows:

1. Open the Threshold dialog box. (See Making color adjustments.)
2. Select Preview.
3. To identify a representative highlight, drag the slider to the far right until the image becomes pure black. Drag the slider slowly toward the center until some solid white areas appear in the image, and place a color sampler on one of the areas.
4. To identify a representative shadow, drag the slider to the far left until the image becomes pure white. Drag the slider slowly toward the center until some solid black areas appear in the image, and place a color sampler on one of the areas.
5. Click Cancel to close the Threshold dialog box without applying changes to the image.

You can use the Info palette readouts of the two color samplers to determine your highlight and shadow values.