Apple Color 1.0 User Manual download pdf (Page 178)

178 Chapter 9 Primary In

Image Contrast Affects the Operation of the Color Balance Controls

There’s another reason to expand or otherwise adjust the contrast ratio of an image

before making any other color corrections. Every adjustment you make to the contrast

of an image changes which portions of that image fall into which of the three

overlapping tonal zones the color balance controls affect (covered in the next section).

For example, if you have a low-contrast image with few shadows, and you make an

adjustment with the Shadow color balance control, the resulting correction will be

small, as you can see in the following gradient.

What Exactly Is Image Detail?

Image detail is discussed frequently in this and other chapters, mainly within the

context of operations that enhance perceived detail, and those that result in the loss

of image detail. Simply put, image detail refers to the natural variation in tone, color,

and contrast between adjacent pixels.

Because they occur at the outer boundaries of the video signal, the shadows and

highlights of an image are most susceptible to a loss of image detail when you make

contrast adjustments. This results in the “flattening” of areas in the shadows or

highlights when larger and larger groups of pixels in the picture are set to the same

value (0 in the shadows and 100 in the highlights).

It’s important to preserve a certain amount of image detail in order to maintain a

natural look to the image. On the other hand, there’s no reason you can’t discard a bit

of image detail to achieve looks such as slightly crushed blacks, or widely expanded

contrast for a “high-contrast look” with both crushed blacks and clipped whites. Just

be aware of what, exactly, is happening to the image when you make these kinds of

adjustments.

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Apple Color 1.0 User Manual Page 178