Category Archives: Luminosity Conversion

Luminosity based black and white conversion methods convert images to grayscale based only on the brightness or luminosity of the image. This is similar to the way black and white film captures only the scene’s brightness. These methods work by discarding the color information. They are destructive methods. This may or may not be a good thing, depending on whether you still need the color information.

Pros and Cons

The advantage of luminosity methods is that they are simple to use.

The disadvantages are:

  1. They ignore color information that could be used to make better black and white images. For example, you can’t use luminosity methods to push the sky towards black or trees toward white like you can with the regular black and white conversion layer.
  2. they don’t keep the color information that you may need later.

Orange
Converted using Gorman conversion

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)

Continue reading Grayscale Mode