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Real World Camera Raw: Image Editing and Image Degradation

Article Description

No matter what you do, edits degrade the data in an image file in three different ways: clipping, and tonal range expansion and contraction. Jeff Schewe shows you how to make the best use of the available bits you’ve captured to produce the desired image appearance while preserving as much of the original data as possible.
Color Space Conversions

Color Space Conversions

Another operation that usually entails all three of the aforementioned types of image degradation is color space conversion. When you convert from a larger gamut to a smaller one, colors present in the source space that are outside the gamut of the destination space get clipped (see Figure 1-7 in the previous chapter for an illustration of gamut clipping).

A significant number of levels also get lost in conversions between spaces with different gammas or tone curves. The bigger the difference between the gammas, the more levels get lost. Figure 2-9 shows what happens when you convert a linear-gamma gradient to a gamma 1.8 working space in both 8-bit/channel and 16-bit/channel modes. Even in 16-bit/channel mode, you see some spikes and holes; in 8-bit/channel mode, about 25 percent of the levels have disappeared.

Figure 2-9 Gamma conversions.

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