Digital Camera Color Adjustments in Photography

The previous adjustments regulate general brightness of the image: in a photograph tin grayscale we regulate the different tones on an only channel; in a RGB color image, CMYK or color indexed to changes a combined channel is produced, meaning in all the channels at the same time. Nonetheless, in the curves or levels dialog boxes of a color image we have a channel selector with which we can regulate the intensity of the colors separately. In Lab mode the general brightness adjustments are made in the corresponding channel ( L channel) and the color adjustments are made in the a and b channels, which are the ones that define the tonality of each point. The color correction is a delicate task because it has to be made with the eye, since we rarely have a neutral gray surface were to do measurements with the dropper tool in the info. In the chapter dedicated to filters we have seen that as in the studio it is normal to have a perfect color balance, in exteriors the color of natural light varies notably, in a way that a color dominant can be justified and give "realistic" information. At the same time, we know that going from a negative to paper or a slide, in the lab there may be error in generalized dominance. Other times we have made photographs with unordinary light conditions, for example in the first or last light of day, or when different light colors are mixed, or when the light has passed through a filtering surface, such as the leaves on a tree, curtains, umbrellas, or is light reflected by a color surface, such as a wall, the ground or clothes. For all these reasons, the number of photographic prints or slides that have a problem with color isn't insignificant. Now we can correct the worst cases and do justice to the scene we are seeing, and had been degraded by a bad printing or abnormal conditions when shooting. Correct the color requires a certain amount of experience and well calibrated instruments. It is necessary to remember some of the concepts we have seen throughout the book:

•  An excess in color, primary or secondary, is corrected by reducing it or increasing the respective complementary value: red with cyan, green with magenta, blue with yellow, and vice versa;

•  An image can't have dominants of the three colors (primary if we are reasoning with additive mode, or secondary if it is subtractive mode), but in two as maximum because equal parts of the three neutralize each other.

Variation Menu

If we don't have experience in the matter, Photoshop offers a submenu which directly offers the different correction possibilities: Image > Adjust > Variations . In the box we can see and buy with the original the different proposed alterations. If the color dominant in the original is strong, we can modify the amount of adjustment in the fine/rough selector. If the image has a double dominant, for example too much green and some blue, we will have to do the process twice, the first time to correct the equal parts of green and blue with more red (the complementary to cyan), accept the change and reopen the box to eliminate the rest of ht green with it's complementary, magenta. This submenu doesn't let you work with adjustment layers.

Adjustment layers

If we already have experience we will get more precise results with corrections made on an adjustment layer. This system is specially recommendable for color corrections, since even though we can undo changes in the image by going back in the history, when we close the image we loose the reference to the original before correction. On the other hand, the adjustment layer is saved in the image and can be edited or eliminated depending on the results. We can even create a layer for each type of adjustment and this way compare the effects of the different menus, since one layer can be inactivated and made invisible by clicking on the corresponding box in layers . First we will open ( Window > Show layers ) and to create a new adjustment layer we can do so from the main menu ( Layer > New > Adjustment layer ) or clicking on the arrow in the box and selecting the option. Next Photoshop will ask what kind of adjustment we need and once it is made and accepted we can see the image has two "floors" now: the background and, on top, the new layer. The layers box distinguishes an active layer (highlighted) from an inactive, and when we want to edit a multiplayer image, with adjustments, text or image, we will have to know what layer we are working with. In a box that is at the left of the layer there is an eye which disappears and the layer becomes invisible. This lets us compare the effect of different adjustment layers or one of them in comparison with the unedited image.

Color Balance Menu

For slight color correction it is usually enough to use the color balance box, where (for RGB, CMYK and indexed color modes) are represented by pairs of complementary colors. For example, to reduce a red dominant we will have to increase cyan (or green and blue at the same time, since both actions are equivalent). The adjustments are made separately for lights, shadows and medium tones. In a Lab mode image, on the other hand, the balance frame only reflects the a (red-green) and b (blue-yellow) for all the brightness levels, since it is regulated independently through the L channel.

"Levels" and "Curves" Menus

In the levels menu the procedure to follow is the same as for general brightness, only now we have to choose the color to be modified in the channel selector . Normally the color correction is made with a gamma regulator (gray triangle). In an image of RGB mode, when we increase the value of the gamma of a determined channel we increase the output level of that color; when we reduce the gamma, the level reduces and increases that of it's complementary (in CMYK mode it is the other way around). This adjustment affects all the brightness levels of the image. For special cases were we need to modify the color value in different brightness levels using the curves menu in a similar way to what we have seen for medium tones.