Apple Aperture Digital Photography Fundamentals - Manual (Page 45)

Chapter 3 Understanding Resolution 45
Understanding How Aperture Uses Floating Point
Internally, Aperture uses floating-point calculations to minimize quantization errors
when image adjustments are processed. Floating-point calculations can represent an
enormous range of values with very high precision, so when adjustments are applied
to an image, the resulting pixel values are as accurate as possible. Often, multiple
adjustments to an image create colors outside the gamut of the current working color
space. In fact, some adjustments are calculated in different color spaces. Floating point
permits color calculations that preserve, in an intermediate color space, the colors that
would otherwise be clipped.
When it’s time to print the image, the output file has to be within the gamut range of
the printer. A pixel’s tonal values can be processed with incredible accuracy and then
rounded to the output bit depth, whether onscreen or print, as necessary. The accuracy
is most noticeable when rendering the darker shades and shadows of the image. The
bottom line is that image processing using floating-point calculations helps produce
extremely high image quality.
For more information about color gamut, see “ Understanding Color Gamut ” on page 34.