nxtr23.pdf

Using Levels and Curves

Request

I would like to enhance the contrast of an image.

Response

A more dynamic image can be created by increasing contrast using Levels & Curves

enhancement.

Before

A dull and lifeless image.

After

Contrast is increased to make the image

more dynamic.

Procedures

STEP 1: Check image contrast levels ............................................................................ 2

STEP 2: Adjust levels..................................................................................................... 4

STEP 3: Adjust the tone curve ....................................................................................... 6

STEP 1: Check image contrast levels

Open an image.

Check the histogram. In general, the spikes on histograms for low-contrast images

(those that are dull and lifeless) are concentrated in the center of the histogram, indicating

insufficient shadows and highlights. The histogram for this image shows the characteristic

concentration of spikes at the center.

The spikes on the histogram

are concentrated at the center.

Enlarging the histogram

With Capture NX Ver. 1.1, the histogram can be enlarged. Click the button at the top right of the

Photo Info palette to enlarge histogram display. Click the same button again to return display to

normal size.

Clicking the button indicated here to

allows histogram display to be enlarged

and reduced.

STEP 2: Adjust levels

Select Levels & Curves… from the Light submenu in the Adjust menu.

A Levels & Curves step is added to the Edit List.

Move the black point and white point sliders in the Levels & Curves dialog toward the

center of the histogram. Keep in mind that too much adjustment will result in loss of detail

in highlight and shadow portions.

Contrast in the image is increased (image becomes more dynamic).

The image histogram in the Photo Info dialog shows a broader range (from left to

right) of spikes than was displayed for the image prior to adjustment.

Move the black point and white point sliders

toward the center of the histogram. By

reducing the distance between the black and

white points, contrast is increased. However,

too much adjustment will result in a loss of

detail in highlight and shadow portions.

Tone curves

Image contrast is increased.

The spikes on the histogram

are more spread out than

before.

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