Finding White and Black Points in Videos
with Color Casts

This image has a very reddish color cast. This tutorial will show you how to easily restore it using two Vegas filters. Color Corrector and Threshold. The first filter is the obvious choice but using the second with it to make your job easier may not be so obvious.

Why use Threshold? Because it can quickly show you the brightest and darkest areas in your image thus making it simpler to set black and white points without injecting the human element which may cause you to pick incorrectly. If you look closely at the image to pick a black point manually you have several possibilities if you just eyeball it. You could pick the shadow at the extreme lower left under the yellow and black road barricade, or maybe you would pick the person's pants or the right sleeve of his shirt, or you may pick under the eaves of the house just left of the post on the far right or you may have picked the shadow under the top edge of larger window frame.

To see which is really the correct choice first set the saturation slider on the Color Corrector filter to zero by moving it to its extreme left position. This removes all color from the image and temporarily gives you a black and white picture. CAUTION. This tutorial ignores the possibility of setting a black and white point too severely that results in blowing out contrast in shadows or washing out details in highlights. That problem will be addressed in a future tutorial.

Now drop the Threshold filter on the event. Push the slider to the extreme left so you have a totally white image. Now slowly drag the slider to the right watching the for first instance of black to appear. We now know the correct choice is the shadow under the large window. (see thumbnail a)

Uncheck Threshold filter so it is disabled and restore the saturation slider to 1.00 in the Color Corrector filter. Use the eye dropper tool of the Low Color Wheel (choose complementary color) to click on the area under the window as identified when viewed with the Threshold filter turned on to set the black point.

While you still may need to click in several places in the preview window to hit the best pixel, you now know the correct area to be sampling. Depending on which pixel you click on you may still get rather drastic changes depending on which pixel was clicked, so don't assume your first attempt will be the best.

Note how the value on the low color wheel changes depending on where you click the eye dropper in the preview window. What's happening is the hue is being shifted by the amount shown to remove color cast. By setting a threshold as a starting point you're assuring the pixel with the lowest (blackest) value is selected as the pixel to adjust from as long as you click on the blackest pixel which is why you may need to try several points since even a minor shift either lighter or darker can have a profound effect on what adjustment is applied.

Repeat for finding your white point, this time starting with the Threshold filter slider at the extreme right position so the image is totally black to begin with when the Threshold filter is on, then move the slider left slowly until you just start to see the first white area. (see thumbnail b) which turns out to be the back windshield of the car. Click on the eye dropper tool for the high color wheel and set the white point clicking in various places of the car's back window to get the best overall result after remembering to first turn off the Threshold filter and again restoring the saturation value to 1.00.

Now once you're happy with the adjustment adjust gamma, gain and saturation. Finish by tweaking the midtones moving up and to the left roughly halfway between Y1 and R to make the image warmer or down and to the right between Cy and B to make the colors cooler. This is the more subjective part. If you have some hues in the neutral range its easier to set midpoint tones. If not, this is where you're real world experience comes in.

I settled on getting a contrast between the fading reddish roof and the more brown siding around the top windows while keeping the barricade the traditional black and yellow stripes while trying to strike a balance for making the grass neither too green or yellow.

For best results carefully monitor changes you make using the scopes feature. Keep the waveform between 100 and above zero.

Two tips from Vegas forum members. Jeremy Knight suggests trying the draw feature when selecting a sample area. Once you have the eye dropper on the preview window instead of just clicking try holding down your left mouse button then dragging the eyedropper to select a rectangular area.

John Meyers reminds us that once you make a sample a future sample leaves the color wheel settings based on your first sample with the eyedropper. So you should double click on that little center control PRIOR to taking additional samples to reset the color wheel to its default center settings before taking additional samples.