Color Correction Workflow
First: If you are new to PS's color adjustment tools check them out in Adjustments with particular attention to the Curves adjustment.
Light values adjustment with Levels
Here's a photo with its light values viewed in the levels (below). Though its color balance is truly rotten to behold, its histogram indicates a reasonable lightness distribution.
All its light values need is a small tweak to the white point slider on the right. This will pull out the highlights (note: a photo for printing might not require this as pure whites can not print and very light grays are preferred).
Hue values adjustment with Curves
Having done the light values we can move onto the hue values. This step might sometimes be preceded by a saturation adjustment with a Hue Saturation.
To get an idea of what the color problem might be we call up the Info Pallet and a sample from the Color Sampler tool. These two things work together, the later lays down a little widget that will pick up the numerical color values from the area beneath the sample point, the former will display these numerical color values. In the Options Bar set the Sample Size to a 3 by 3 or 5 by 5 average (a point sample can somtimes yield unpredictable results). The choice of the sample area is crucial:
- It must be from an area of the image that is neutral (grey), but as a result of poor color balance it isn't. A white wall is ideal (or in this case a grey floor).
- This point must ideally be a low value neutral (dark grey not light grey).
Heres a fact: a grey is a grey if its RG and B values are all the same. So.... your job as a color balancer is to make this happen. Generally it is the red and blue values that are moved to match the green. This is because the green channel of an image is where the lightness values of the image also live. If, in the course of a color adjustment, the lightness values are also affected then this is a bad thing.
Now open up the Curves Adjustment. You will notice that the three color values in the Info Pallet are now paired with identical cousins. These are before adjustment and after adjustment values.
Go to the Red channel from the pull-down menu of the Curves and Command Click anywhere near the Color Sampler Tool widget. This will set a point on the curve that corresponds to the value of the grey floor. Then use the Arrow Keys to push this point on the curve up till the after value of the red is equal to the green value.
Now go to the Blue channel. In ideal circumstances you should follow the same procedure as you did to the blue channel (i.e. make it equal to the green). However, as this is such a horrible color-cast photo, the blue channel is too out of whack for this to be possible. If you tried your curve would look like this:
Apart from the result looking weird, the curve also looks wrong. How so? We... any curve adjustment that flatlines (circled) is a bad thing. It equates to compression of data: a whole range of varied values being squashed into one value (in this case zero in the blue channel). Instead an adjustemnt should be made by pulling down on the top right hand corner point.
Though the floor looks fine, the result is still far from perfect. Two neutral balances can not naturally be done within the same image without one canceling out the other. The solution is to do two separate ones (each derived from the same original) and mask them against each other.
N.B.: a mask that is used to separate a figure from its background is very, very, very different to one that is needed to mask out a color adjustment. Such a mask must be soft (painted with a big, fluffy brush). Hard-edge mask separating color adjustments usually look dreadful.
The final file was quite demanding, requiring three adjustments: one to the floor, one to the centre of the wall and one to the right hand side of the wall. It also needed a 'hack' in the form of a layer set to Saturation blend mode and painted on with black. This will desaturate targeted areas (in this case the highlights). I find this method easier and more reliable than making yet another adjustment layer CAUTION: this is most definitely a hack and, if used excessively (or even moderately), will make your image look 'grey scale'. Even grays in a color photo require color noise in order to look natural.
- On the whole it is VERY bad practice to attempt a color correction and an aesthetic adjustemnt at the same time. They are completly different things to be attempted with different operations.
- A curves adjustment should, on the whole NOT be on the RGB composite curve as well as the separate R,G and B curves. Such multiple adjustemnts are much better distributed across two adjustments.
This demo file for this page is in the Assets page.