:: Color Correction with Adobe Photoshop - Part 2

Color Modes Demystified

This article is meant for scuba divers with some form of fundamental knowledge in Adobe Photoshop. For scuba divers with no domain knowledge on Adobe Photoshop, please attend the PADI Digital Underwater Photography course prior to reading this article.

Let's begin. In a simple, real world approach Adobe Photoshop has different color modes designed for different function in the world of media.

Bitmap: We would use for some line art in low end situations, doesn't support color on a printing press but background shows through as transparent. Also used for wallpaper on PC computers.

Grayscale: For black, white and shades of gray., When you use this mode all color information is lost. However you must convert to grayscale before you make it a duotone. This mode doesn't support alpha channels.

Duotone: This is when you want to add some depth or color to a b&W image, or just get a trendy effect. A duo tone lets you choose 2 ink colors on your image and will print as a 2 color job on the press. There is also a Tri-tone -which has 3 colors and a quad-tone that has 4. You can produce some very sharp black and white (Grayscale) images with this and it is used in photography books all the time.

RGB: Uses the computers colors (Red, Green, Blue) and is the best option for the web or electronic publishing. Also called additive colors. Attempting to use this color mode to adjust your underwater images would not yield the real colors. Most of the time, the "corrected" images will have unwanted colors or "over colored" effect.

CMYK: Color printing presses print with 4 ink colors Cyan, Magenta, yellow and black. If you look at a magazine close up you will see tiny patterns of dots, these dots are arranged in different patterns and sizes to fool the eye into seeing colors that are not really there, e.g. brown etc. This method is used in most full color printing. I would only use this if you are going to a press. The disadvantages are, the image is a third larger than RGB, and you will lose some brightness as CMYK does not support as wide a tonal range as RGB. Also called subtractive colors.

Scuba Divers can ignore this color mode completely unless they want to print their photos

Lab: This is a mode that produces consistent colors across different devices. Used where you need to keep exact colors. This color mode is most suitable for handling underwater color correction.