Nikon Capture NX2 user manual Levels & Curves

Levels & Curves

❏The Levels & Curves and the LCH Tools

The Levels & Curves tool controls the distribution of tones in the red, green, and blue channels and in the RGB master channel, and provides visual feedback on the amount of tone information lost through editing. The LCH tool is a better suited to making fine adjustments to luminosity (brightness), color saturation, and hue; note, however, that changes to these settings may produce results that exceed the dynamic range of the RGB channels.

❏Auto Contrast Settings

Auto contrast, shadow, and highlight settings can be adjusted in the “Levels & Sampling” tab of the “Preferences” dialog.

❏The Curve Edit Display

Although values for input and output in the Levels & Curves tool range from zero to 255 (eight-bit precision, familiar to users of other image editing software), the results of any changes to curves are calculated at a precision of sixteen bits. This allows twelve-bit RAW data to be modified without lowering the quality of the output.

❏The Histogram (RAW / 16-Bit TIFF Images Only)

To reduce display times when dealing with large amounts of image data, Capture NX 2 may display a histogram containing vertical lines.

❏Sampling White Point or Black Point for the Current Channel

By default, sampling sets the white point or black point for all channels and displays the master channel. To set the white or black point for the current channel only, sample the image while pressing Ctrl (Windows) or command (Macintosh). Mid-point cannot be sampled for a single channel; regardless of the channel currently selected, sampling the image for mid-point always sets the mid point for all channels and displays the master channel.

❏Gamma

Gamma (also written “γ”) is a fundamental property of video systems which determines the intensity of the output signal relative to the input. When calculating gamma, the maximum possible input intensity is assigned a value of one, and the minimum possible intensity (no input) is assigned a value of zero.

Output is calculated by raising input to a power that is the inverse of the gamma value (output = input (1/ γ)). In practical terms, raising the gamma value has the same effect as moving the midpoint slider to

the left, raising mid-tone output values and brightening the image while leaving the maximum and minimum values untouched. Lowering the gamma value has the same effect as moving the midpoint slider to the right, lowering mid-tone output values and darkening the image. The default value for gamma is one, which produces a linear curve in which input and output values are the same. Gamma can be set to any value between 0.05 and 6.00.

❏Opening NEF Files Saved in Nikon Capture 3.5x or Earlier

In Capture NX 2, changes to color balance apply before changes to curves. In Nikon Capture 3.5 and earlier, changes to curves were applied before changes to color balance, with the result that settings may change when the images saved in Nikon Capture 3.5x or earlier are opened in Capture NX 2.

258Chapter 28 — Appendix: Additional Notices Levels & Curves