Chapter V, Printing Digital Images: Lesson III Using Software to Adjust the Image http://www.kodak.com/country/US/en/digital/dlc/book3/chapter5/lesson3/p01.shtml

Once a picture has been digitally captured, it may be necessary to use an image-processing program to optimize the image for printing. There are a number of basic software programs available that make it easy to enhance several aspects of a picture.

Generally speaking, the goal in making image adjustments is to create a picture, which is pleasing to the user. This may require making adjustments to:  Brightness Contrast Color Sharpness Cropping In this lesson we will look at each one of these adjustments to see how image- processing software can improve picture quality.

Whenever possible, it is best to make basic adjustments when the picture is originally captured. Exposure, color and composition can be effectively control by properly using adjustment features available in most digital cameras and scanners. Refer to your User’s Guide as needed. Many of these adjustments involve personal taste. Which means artistic or creative decisions may override any hard and fast rules; however, some basic recommendations can be made which will result in pictures that most viewers would find appealing.

One of the first things to consider when making adjustments to a picture is its overall tonal range. Tonal range refers to the difference that exists between the lightest (highlight) and darkest (shadow) areas of the picture. Pictures that have a wide range of tones are said to have a wide dynamic range. When making adjustments to brightness and contrast settings, the goal should be to create a picture that has detail in highlights and shadow areas with a wide range of tones in between.

While a picture’s tonal ranges can easily be adjusted using image-processing software, there are limits to what can be done. Two factors that effect the amount of change that can be made are: The tonal range of the original subject The exposure that was used during image capture

Tonal Range of the Subject: Some pictures will contain subjects with a limited range of tones, mostly highlights or shadows. These type of pictures are sometimes said to be high key or low key No amount of brightness or contrast adjustment will create additional, natural looking dark tones if there were none in the original scene.

Exposure: Over exposures (allowing too much light to strike the sensor) will result in pictures with little or no detail in the highlight areas Under exposure ( not allowing enough light to strike the sensor) will result in pictures with little or no detail in the shadows or dark areas.

Brightness adjustments control the overall lightness or darkness of the picture Improperly exposed pictures can be improved to a certain extent using the brightness controls in image-processing software

In setting brightness adjustments, the goal is to strike a balance between highlight and shadow levels.

Contrast refers to the number of mid-tones that exist between highlight and shadow areas in the picture

High contrast pictures have very few mid-tones High contrast pictures have very few mid-tones. They are dominated with areas of very dark and very light tones with little or no transition between the two. A good example of a high contrast subject would be a zebra with its black and white markings Low contrast pictures are flat and muddy looking with little tonal difference between highlights and shadows An example of a low contrast picture would be a white rabbit in a field of snow.

Contrast adjustments should be made together with brightness settings. Use brightness to set the lightness or darkness of highlight and shadow areas. Use contrast setting to adjust all the other tones in between. Setting contrast levels too high will cause mid-tones to disappear. Setting it to low will cause mid-tones to appear the same, resulting in a muddy looking picture.

Color balance refers to how accurately scene colors are reproduced in a picture. There are many variables that effect color including: the type of light in the original scene, camera and scanner settings, monitor settings, printer settings, and the type of light that is used to view the final print.

Generally, color adjustments are made to remove unwanted color casts in the picture. Color casts appear as extra color in white highlight areas and in middle gray tones The first step in correcting an unwanted color cast is to identify the color of the cast by categorizing it as being closest in appearance to one of 6 basic colors; Red, Green, Blue, Cyan. Magenta, Yellow.

In most image-processing software, these colors are grouped according to a relationship known as complementary colors. Simply stated, complementary colors are colors that tend to neutralize each other.

Once the color cast has been identified, adjustments are made by moving a slider control away from the color cast and toward the complementary color For example, if there appears to be a blue cast in the picture, moving the slider away from blue, toward yellow (the complement of blue) would neutralize the blue cast. As the slider continues to move in the yellow direction, the blue cast disappears, however, if moved too far, the picture will take on a yellow cast.

The goal in making color adjustments is to remove any unwanted color cast without introducing a new cast. Look for color casts to first appear in neutral areas.

Picture sharpening refers to an image-processing procedure that makes a picture look crisp, with sharp detail between adjacent areas in the picture. Too much sharpening can result in pictures that look grainy and distorted. This adjustment is not meant to correct original errors in focusing.

The visible results of sharpening can be subtle The visible results of sharpening can be subtle. Look for the effect to be most noticeable around adjacent objects that have hard edges. For example, sharpening will increase the "snap" at the edge of text information that may appear in a picture. Too much sharpening will produce distortions that will appear as fine, high contrast, lines around the edges of objects in a scene

Although sharpening adjustments can be previewed on a computer monitor, final decisions about how much sharpening should be applied to a picture should be based on what is seen in a test print.

Cropping involves deciding which parts of the picture will be included and which parts will be left out of the final print.

Extensive cropping in a digital picture is not recomended unless you intend to make a small print. Enlarging the cropped part of the image reduces quality. A much better approach is to compose your subject in the camera, before taking the picture, filling the frame with the subjct.

The composition of a picture can be easily enhanced using the cropping tool. Subjects in the picture can be repositioned creating a sense of balance in the frame and providing strong center in interest.

A simple way to create a pleasing composition in a picture is to use a technique known as "The Rule of Thirds" When dividing a scene into thirds both vertically and horizontally, the dividing lines intersect in four places. Any of these four intersections provides a pleasing position for the picture’s center of interest. Even though the cropping tool can be used to improve the composition of a picture after its been taken, Its always advisable to make decisions about the subject’s size and placement when the picture is originally taken.