Be prepared to learn something new today, and I am not only talking about the Sepia Effect in Photoshop. Sepia is the dark brown pigment that comes from secretions of the ink sac of a Cuttlefish. That ink was then mixed in with other chemicals that resulted in the tones of the photograph to be in shades of brown instead of gray, back in the 1880s. They have since developed artificial toners and now with Photoshop you don’t even need the chemicals

Every image opened in Photoshop runs in a particular color mode. The names of some might be familiar to you; have you ever heard of Grayscale, RGB, or CMYK?

Understanding the different color modes is a vital step to becoming a good designer. For example, it would be detrimental to your efforts to compose an image for print using the RGB color mode, as colors may not appear on paper as they do on screen.

What follows is a breakdown of the different color modes available in Photoshop, as well as suggestions for how they might best be put in to use.

Bitmap

Not to be confused with the Windows file format BMP, an image using the Bitmap color profile is displayed in true black and white. That is, no shades of gray in between – each pixel is displayed strictly in either black or white.

Shaded areas are produced by a pattern of black and white pixels, though unless you’re using a very high resolution (1200 dpi and over), the images are bound to turn out with jagged lines (see example below).

Bitmap images can be used for the web, as well as commercial print. It’s not really suitable for much else.

Grayscale

Grayscale is the color mode most refer to as black and white. Each pixel can be displayed in a total of 256 shades ranging from black to white.

Grayscale images are usually printed with just one ink color, the different shades of gray created by heavier and lighter distributions of ink.

RGB

RGB stands for Red, Green and Blue. It is used most widely for images displayed on screen. Photoshop uses it (when in different color modes, what’s displayed onscreen is an RGB representation of how the other mode will appear upon output), as does this web browser, and so does every application running on your computer. Digital cameras use it, your mobile phone, and so does any digital device displaying images through a screen.

RGB is an additive color model. An additive color model involves light emitting directly from a source – the colors of light usually being Red, Blue and Green. When these three lights are mixed in equal intensities, you get white. Much the same, a wide gamut (range) of colors can be produced by mixing various intensities of these lights.

For example, mixing equal parts blue and green produces the color cyan, when using the RGB color mode. Equal parts red and green yield the color yellow.

What this means is that every single pixel being displayed on screen is a mixture of particular intensities of Red, Green and Blue.

Of all color modes, RGB boasts the largest color gamut.

As previously mentioned, the RGB color mode should be used when working for any image meant to be displayed on a screen. That is, web design, editing digital photos, etc.

CMYK

CMYK stands for Cyan, Magenta, Yellow and Key (black). It is used mainly for commercial print jobs – advertisements, magazines, books, posters, etc.

Contrary to RGB, CMYK is a subtractive color model. Unlike in an additive color model, where white is produced from a mixture of different colored light, in a subtractive color model, the more color mixed together (paints, dyes, inks, etc.), the closer to black you will get.

It is interesting to note that even though the average personal inkjet printer uses ink tanks of Cyan, Magenta, Yellow and Key, its software is compatible only with RGB color data.

Some high-end inkjet printers contain a piece of hardware called a RIP (raster image processor), that tricks your printer into thinking it’s a commercial printing press, allowing it to receive color data in CMYK.

Indexed Color

The Indexed Color mode is ideal for web graphics, such as navigational buttons.

The pixels within an image using the Indexed Color mode can be one of up to 256 different colors.

Because of the low number of available colors, the file size is kept exceptionally low. As already mentioned, this is ideal for web graphics. File types using this format are GIF and PNG-8.

It is not ideal to create an image meant for printing in the Indexed Color Mode.

Lab Color

Pronounced L-A-B, this color mode, like RGB, contains three color channels. They are Luminance, the ‘a’ channel (containing color data from a green to red spectrum), and the ‘b’ channel (containing color data from a blue to yellow spectrum).

Lab color was designed to resemble human vision, and its Luminance channel closely matches human perception of lightness.

It isn’t really possible to output images in Lab, so using the color mode is really a middle step in the workflow, before converting the image back to either RGB or CMYK.

Duotone

Duotone is a specialized color mode used for commercial printing. Quite simply, it is an image printed with only 2 different colored inks.

Think of a sepia toned image, only with greater control.

Though only using two inks might sound good for regulating ink consumption with your inkjet, it isn’t really possible, seeing as that the process requires a specially mixed ink.

In addition to duotone, you can also have monotone, tritone and quadtone, which uses one ink, three inks and four inks to create the image respectively.

Multichannel

Multichannel is much the same as Duotone, the difference being that while in Duotone, inks are generally spread across the paper, in Multichannel, the ink is used in specific areas.

Like Duotone, Multichannel is only suitable for commercial printing presses.

Multichannel is ideally used in situations such as creating logos.

Using this information, you should now know which color mode best suits whatever project you happen to take on. Having an understanding of the different color spaces is one of the fundamentals of design, and this new knowledge should serve you very well in the future.

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