understanding color correction outline color casts defined channels defined auto methods of color...

Understanding Color CorrectionOutlineColor Casts DefinedChannels DefinedAuto Methods of Color Correction-- LevelsManual Methods of Color Correction-- Curves

Color Cast Skin

Color Casts-- Defined

An image that is not color balanced is said to have a color cast, as everything in the image appears to have shifted towards one color or another.

Sometimes this can be deliberate and is considered to look very nice, such as with film photography. ---------------------->Shot with Kodak Provia 400 film, which when overexposed gives an orange-ish gold color cast.

Color Casts-- DefinedAny image that is taken digitally with an improper white balance is bad news. It does NOT look deliberate (eventually your eye will be trained to see this). It most definitely needs color corrected. --------------------------------------------------->

BAD!!! >:-(

Better :-/

Sometimes it will seem as though an image does not need color corrected, but

actually it looks much better when it is! :-)

<----------------------------------------------------

Color Casts-- Defined Photos shot under incandescent lighting, as well as older

photos, often have a yellow color cast. Outdoor photos tend to have a blue tint. Color balancing, also known as white balance (or grey or neutral balance) is the removal of this color cast.

RGB Channels-- Defined

When you work with Levels and Curves, you have the option of working with individual channels. When you open a photograph in Photoshop, it will

already contain a number of channels. You can view them in the Channels palette by choosing Window > Channels.

An RGB image such as a photo will have four entries in the channel list: one red, one green, one blue, and a composite channel made up of all three channels.

RGB Channels-- Defined When you click on a channel such as the Red channel in the

Channels palette, the other channels will be rendered invisible and you will see a grayscale image that represents the red in the image. In an RGB image, the areas that are darkest in the grayscale channel are those in which there is little of that particular color. The areas that are lightest are those with the most color.

Auto Methods of Color Correction One Quick and easy thing to do would be to go to

Image>Auto Color. You may see little difference, or a lot of difference that you

DO NOT want. Or, you may find that you want a little more control.

If you do Auto Color, make sure you are creating a Duplicate Layer.

Auto Correction With Levels To properly removing a color cast in a photo we must

correct the white balance of the image.

Notice three eye droppers in the levels (or curves) dialogue box. They are used to select white, grey and black points within in your image.

Auto Correction With Levels When there is a color cast in an image, it is as if the image is

"confused" about what is supposed to be white, black and neutral grey. We "fix" the problem by showing Photoshop where these points of reference can be found in the photograph with these eye dropper tools.

First, check your settings for the eye dropper tool in Photoshop.

Make sure it is not set to Point Sample, which only evaluates a 1 pixel square. Here, the settings are changed to a 5 X 5 average pixel sample.

Auto Correction- Black and White Areas- Levels

If we want to improve our accuracy in selecting the whitest and blackest areas in an image, we need a non-subjective method of making the choice. By choosing Image > Adjustments > Threshold, Photoshop can do just that for us.

Auto Correction- Black and White Areas- Levels

The dialogue box has an image that looks similar to a histogram, and the image turns into a black-and-white preview.

Auto Correction- Black and White Areas- Levels

Our first objective is to find the darkest black portion of the image. Begin by sliding the middle slider toward the left.

The image will begin shifting toward all white. Stop sliding just before the entire image turns white (you may want to zoom in on whatever remains black).

From here you can select the dropper tool in the tool bar, set the sample to 5x5, hold down shift and mark a point in one of these areas left black.

Auto Correction- Black and White Areas- Levels

To find the truly white areas, do the opposite.

Auto Correction- Black and White Areas- Levels

This is slightly more accurate because in some cases, areas you may think are pure white (such as Christopher's shirt, the threshold do not indicate to be white.

You can see on the next slide that when I selected the area in the top right corner that was first to appear as white in the threshold, gives a much more accurate color correction!

Auto Correction- Black and White Areas- Levels

<--------Selecting the shirt as the white area.

Selecting the spot in the top right corner as the white area.------------>

More Precise Auto Correction- Finding Neutral Gray

There are times when we need absolute perfection in color balance, and Photoshop has a way. The tool is the grey eyedropper in the middle of the layers adjustment pallet. The only problem is this: we must click on an area in the image that is EXACTLY neutral grey (50% black) to get perfect results.