Convert Color to Grayscale

Image>Mode>Grayscale

The quickest but not necessarily the best output, since it converts all color channel black/white images equally.

Grayscale versions of images have much smaller file size, because the color information is gone.

Channel Mixer Adjustment Layer

This adjustment allows you to adjust the grayscale output differently in each color channel, which improves the resulting black and white image.

• Download the image subwaytrain.jpg . Open it in Photoshop.
• Click on the Create new fill or adjustments layer icon at the bottom of the layers palette (a circle that is half black) and choose Channel Mixer. Or click Layer>New Adjustment Layer>Channel Mixer. Either will open the Channel mixer dialog box.

• Click the Monochrome checkbox to turn the image to a grayscale one. The output channel changes to Gray.
• Adjust the sliders in the individual channels to control the appearance of the resulting black-and-white image.
• The combined percentage is supposed to be 100%, but going beyond that limit can yield interesting results.
• Experiment with different settings in each channel.
• Slight constant slider adjustments will affect the image. Sliding the constant slider to the left darkens the image overall, and to the right lightens the image overall.
• Create an additional Levels adjustment layer to push the contrast even further.

Selective coloring of part of grayscale image

Convert part of an image to grayscale and leave the rest in color by painting a layer mask.

Try it

• Download and open 002flowers.jpg in Photoshop.
• Create a duplicate background layer [CTRL+J]
• Click on the duplicate layer to select it, and then click Image>Adjustments>Desaturate to get rid of the colors.
• Add a tint to the grayscale color by clicking on the grayscale layer and clicking Image>Admustments>Hue and Saturation.
• Check the colorize checkboxand move hue slider to 221 and saturation slider to 12 to change it to bluish color.
• Turn the layer into a layer mask: with grayscale layer still selected, click Layer>Layer Mask>Reveal All
• with the Layer mask thumbnail (and not the layer) selected, check to see the foreground color is black and the background color is white.
• Pick a hard-edged brush, and paint the layer mask to reveal areas of color that you want to shine through.

Resulting image compresses well because of reduction in color palette.