Apple Aperture 3.5 - Manual (Page 298)

Chapter 7 Make image adjustments 298
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To adjust the white clipping point: Use the “Auto adjust White Clip” parameter controls.
Use the Auto Adjust White
Clip slider and value slider to
add tolerance to Auto Levels
adjustments when evaluating
colors beyond white.
Dragging the slider to the right increases the tolerance of Auto Levels adjustments to colors
beyond the analyzed white point in the image.
3 After the black and white clipping points are adjusted, click either the Auto Levels Combined or
Auto Levels Separate button in the Levels area of the Adjustments inspector or the Adjustments
pane of the Inspector HUD to view the effect on the image.
Manually adjust levels in an image based on luminance
To manually adjust the overall tonality of an image without affecting its color cast, you use the
Levels adjustment controls based on a histogram that shows luminance. When the histogram is
set to show luminance, it displays the cumulative brightness values for all three color channels
for each pixel.
Before Levels adjustment After Levels adjustment
67% resize factor