Convert to 8-bit Intensity
The Convert to 8-bit Intensity command converts an RGB image to an 8-bit grayscale image with pixel values between 0 and 255. The R, G, and B channels are combined to a single value using the standard grayscale conversion weights (0.292, 0.594, 0.114). If you wish to convert an RGB image to a 16-bit image using any other weight values, use Convert to Grayscale prior to the present command. If the RGB image is already in grayscale form, then this command will weight R, G, and B equally.
The Convert to 8-bit Intensity command opens from the Image Window > Process > RGB Images menu when an image or image set is displayed in the top-most window.
Working with RGB Images, Convert to 16-bit intensity, Convert to Grayscale