Adjusting color and contrast
Let´s say that you have shot a photo with the right exposure and the color balance. Should you kick back in your seat and start calling the agencies? Not quite. Is your image really looking its best? How can you create a colourful, luminous image?
Photoshop (or the image editing program of your choice) has several tools which can help you to improve the contrast and the color. The most basic one are the curves and hue/saturation.
The curves option in Photoshop allows you to adjust the tonal range of an image. It also allows you to adjust the color channels individually. You can maximize your work by saving the settings applied to a given image and applying the same settings to similar images.
Below is an explanation of the “Curves” functions:
- Here you can choose whether to work with all of the channels at once (RGB mode) or you can work with one channel at a time (ex. Red).
- The shadows are represented in this part of the graph. Here we can adjust the black value.
- This area represents the image midtones.
- Here the highlights are shown.
- You can use these 3 eyedroppers to assign the black, grey, and white values in an image, creating an automatic curve.
- This option allows you to choose between a curve showing the subtractive colors (pigment) and one showing additive colors (light). The pigment visualization will show the highlights (0%) in the bottom left corner and shadows in the upper light (100%), while the light visualization will show the opposite, shadows in lower left and highlights in upper right (0-255).
When editing the curves of an image, you should keep the “information” window open in order to see how your changes are affecting the tonal values.
Here is a properly exposed image before adjustments.
After adjusting the curves...
A few minor adjustments allow you to brighten up the highlights and midtones, but by preserving the black value, we don´t lose any density in the shadows. Presto! An image with a nice contrast and bright colors.
This option allows you to adjust the tone, saturation, and luminosity of a particular range of colors found within the image, or to adjust all the colors at once. Just like the curves tool, this tool allows you to save the settings in order to apply the same changes to other images.
Edit: allows you to select which colors will be adjusted.
Hue: allows you to move around the color wheel. Positive values show a rotation towards the right and negatives values show a rotation to the left. The values range from -180 to +180.
Saturation: (color purity) is represented on a radius. The values can be between-100 and +100.
Lightness: The lightness values can be between -100 and +100.
Colorize: allows you to add color to a grayscale image converted to RGB or create a duotone by limiting the color values.
Below is an image before any adjustments:
Since the colors of the image were rather dull, we have added 20 points of saturation.
Check that the saturation has been implemented properly, and that it hasn´t produced posterization (brusque changes in color, rather than gradual shifts). Be especially careful with red and yellow because they tend toward posterization.
After adjusting the saturation, the image is brighter and more colorful.