Gamma correction is used to account for differences between the image that is being sent to a computer monitor and the image that is actually displayed on the monitor. Different monitor manufacturers and models may display slightly varied brightness levels for a specific image. Properly setting an image's gamma correction value in Adobe Photoshop will assist in correcting this variation.
Open the image to be corrected in Photoshop. Gamma correction cannot be applied if no image is open or if the image is empty.
Click on the "Image" tab, expand the "Adjustments" sub-menu, and select the "Exposure" option.
Drag the "Gamma correction" slider to the desired value or type a numeric value. Adjust the image until it matches the desired brightness and intensity to match the original image.
Click "OK" to apply the gamma correction to the document. If this produces undesired results select "Undo" from the "Edit" menu.