Category Archives: Photoshop

Photoshop related posts.

Parliament Hill – Example

There may be times when you want to apply different conversion methods to different parts of the image. Here’s how.

UPDATE: This tutorial uses some obsolete methods such as the hue/saturation method. I created this example about ten years ago, before Photoshop CS3 introduced black and white filters. If I were to redo this today I would use different conversion methods. However this tutorial, along with Selective Color, is a good example of how to use color selection during black and white processing. – DK

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Lab Color Mode

Lab color mode is a mode in Photoshop. Lab is different from RGB color mode in that it separates the luminosity information into it’s own channel. Lab mode has three channels: L, a and b.

The L Channel contains the image’s luminosity information. This allows you to manipulate the image’s luminosity without affecting it’s colors. The L channel is similar to black and white film in that it only records the image’s luminosity.
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Grayscale Mode

Grayscale mode is a color mode in Photoshop. In grayscale mode, images are represented using only shades of gray rather than the full pallet of colors.

In RGB mode, the color of each pixel is stored as three numbers, or channels (nnn, nnn, nnn). If all three channels have the same value then the resulting color is a shade of gray.

Black (0,0,0)
Gray (80, 80, 80)
Gray (160, 160, 160)
White (255, 255, 255)

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Selective Color

Hand-coloring has been used by photographers for over a century to add color to black and white photographs. This was done by hand painting the photograph with oil or watercolor paints. Unlike toning, which applies the same color to the entire image, selective coloring applies one or more colors to specific parts of the image.

The usual way to apply selective color is to use a mask and a solid color layer to apply color to specific parts of the image. However, by using Color Range selection and curves, you can create a more subtle look.

Selective Color

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RGB Color

RGB (Red, Green, Blue) is a way of describing color. Each color is described by a set of three numbers. For example, (102, 51, 255) describes THIS COLOR.

The color’s RGB value, written (n, n, n), describes the intensity of the red, green, and blue channels that make up that color. The range of values for each channel depends on the channel’s bit-depth, or how many bits are used for each channel.

Bit Depth Range
8 bit 0 – 255
16 bit 0 – 32768
32 bit 0.000 – 1.000

For example, in an 8-bit RGB each channel can have a value from 0 to 255. Zero means no brightness for that channel, 255 means maximum brightness. 8 bit RGB colors can range from (0, 0, 0) to (255, 255, 255) and every combination in between, or 2563 = 16,777,216 different colors.
Note that a 32 bit RGB should have an integer range between 0 and 232-1 or 4,294,967,295. However, this is normalized to a decimal value between 0.000 and 1.000.

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