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Color Correction 101

Color Correction 101

A few simple steps can save an improperly-shot scene or improve one that is less than brilliant.

A few simple steps can save an improperly-shot scene or improve one that is less than brilliant.

Don't let the interface of the Color Corrector 3-Way window intimidate you (OK, some of us editors were intimidated by this less-than-intuitive window). Keep in mind that, even though this article will show you a few simple techniques, this color-correction tool and others are quite robust, and some editors make healthy incomes concentrating on this fix-it-in-post endeavor.

Let's start with some tools that will help greatly. The first is an NTSC monitor. Though we are aware that many editors work without this essential tool, due to its hefty sticker price (some over $10,000!), we really cannot see the true colors that viewers experience on a television set from our computer monitors. A consumer television set is better than no outside monitoring of the picture, but a true NTSC monitor is best. If you are sure your finished piece will live only on the internet, no monitor is necessary. But if you are making DVDs of your final project (which are usually viewed on television sets), or the Discovery Channel calls and wants to use your piece on air, it's a good idea to view your project through a non-computer monitor before output.

The other two tools we will use won't cost you anything extra if your editing software has them built in. They are two of the four video scopes: the waveform monitor and the vectorscope. We covered these tools in The Right Caliber, the May 2007 Editing column. Again, we will admit that these highly technical-looking scopes intimidated some of us at first viewing, but learning the basics of how to read them to assist in altering light and color will great improve our images.

The video scopes give us invaluable information on color and brightness within a single clip and even help us correct white-balance problems originating in production. They will also quickly tell us if our image is not "broadcast safe," enabling us to bring it within the safe zone with our color corrector.

Invention of the Wheel

Sir Isaac Newton gets credit for developing the color wheel as we know it, with the primary additive colors red, green and blue and the secondary colors magenta, yellow and cyan, formed by overlapping primary colors. The center of a color wheel has no color or is white. As you travel away from the center, colors become more saturated.

Two Color Wheels

Please notice that we are working with the Color Corrector 3-Way filter in this exercise. There is another tool called simply the Color Corrector. We use the 3-Way for "primary color correction," which incorporates the manipulation of the overall color balance of the entire image. In a later article, we will cover the Color Corrector tool, which lets us manipulate individual colors (often called "secondary color correction").

Getting to Work

Many higher-end editing programs will have a "color correction" layout that you can find under the Window pull-down menu. Most modern editing programs will let you work with most of your color correction in real time, that is if your processor is fast enough and you have a decent amount of RAM.

You can find the Color Corrector 3-Way in your Video Filters folder; usually you'll locate it under Color Correction.

The 3-Way has a visual interface as well as a numeric interface. We find it easier to work in the visual interface.

Most Color Corrector 3-Way visual interfaces show three color wheels with luminance sliders beneath them, along with other controls, including an eye-dropper. In primary color correction, we suggest you concentrate on image contrast first, then work on color balance. The eye is more sensitive to changes in contrast than to differences in color, so this is the best place to start. We use a work flow that starts with setting the black levels, then moving on to the white levels and ending with adjustments to the mid-tone levels.

Start with Luminance

By moving the black level luminance slider, you affect the overall depth of the black levels in the image. By looking at the waveform monitor, you can see if your black level values are above 0%, or what is known as Black, and move the black level slider to the left.

If you keep moving that slider to the left, bringing your black level values down to the 0% luminance line in the monitor, you will start to "crush your black levels." For example, if you can see detail of dark hair, you can crush the black level of the image by sliding the luminance to the left. The tonal range in the dark hair that gave visual details in the shadow area are "crushed" into all black, eliminating the shadow detail.

Make sure you check the levels for the entire clip and not just one frame of the image. Changes in the action will cause changes in the luminance levels.

If your white level values go over 100% luminance, into Super White, your image is not broadcast-safe (look at your waveform monitor to see if there are any dots above 100%). You can slide the luminance slider under the white level color wheel until you see the values for white levels drop below 100% into network safe range.

Finally, we want to alter the mid-tones, which will affect the overall exposure of the clip. This slider affects mostly skin tone or middle gray in most shooting situations of a properly-exposed image. If someone's face looks too bright or too dark, the Mids slider could bring them back into normal exposure. Every color corrector that we have used has an on/off check box that will enable you to view your changes and the originally-shot clip with the click of a button.

When color-correcting a certain clip, look at the top of the Viewer window, where you can find the name of the clip, to make sure that you are working in the correct clip. It is easy to think that you are working on one clip, while you're really adjusting the color of another clip. You should also know that adjusting any one wheel (or tonal level) also adjusts others. For example, though you adjust mostly the darker parts of the image when you move the black-level luminance slider, you also adjust white levels and mid-tones a bit. The same is true with the other two wheels. This keeps more realistic gradations, but it means you may need to make slight adjustments on the other two wheels when you are drastically changing one wheel.

You will want most color correction to be subtle, unless you are going for a very stylized look. Various keyboard commands or use of a mouse with a scroll wheel can help you fine-tune a look. Check your user's manual, as these effects differ in various editing programs.

Next We Adjust Color

Use color balancing to remove or intensify a colorcast in a scene. The vectorscope will be your friend here. If you look to the center of each of the color balance wheels - the black levels, mid-tones and white levels - you will see a small, gray, circular object called the Balance Indicator. By clicking and dragging this small circle towards the outer part of any wheel, you will see that you adjust the hue that corresponds with each of these tonal levels, respectively, to the color you are moving the indicator towards.

This control works in small increments, so small movements might be difficult to notice. Again, the on/off check box will help you see the changes you have made. It may seem as if you aren't changing the tint or shade much, but unclick that box, and you can easily see your changes. Again, you want this to be subtle, so move in baby steps and continually check against the original or against an image you are trying to match. The more you drag that gray dot to the perimeter of the circle, the more saturated the hue that affect the tonal range becomes.

Many color wheels have a reset button on the lower right of the wheel. Just like focusing a camera, you move in and out, more extreme and then less, until it looks right. If you are not happy with current changes, just reset to eliminate all changes and start again. Note that adjusting the mid-tones color balance wheel has the greatest overall effect on the image. This is because the mid-tones are the majority of your color information in a typical image that is exposed properly.

On the color wheel, each primary color is opposite its secondary color. These opposite colors on the wheel are complementary colors. If you drag towards one color, the color on the opposite side of the wheel lessens. For example, if you move towards red, you intensify red while reducing the cyan values in the image.

Quick White-Balance Correction

There is a quick trick for simply correcting an image with improper white balance. Click on the eye-dropper under the mid color wheel, and then click on an object in your clip that should be white. This tells the filter to adjust the overall image in a way that makes this object white, thus adjusting the improper balance of the whole image. See, not too intimidating.

You've Graduated from Color Correction 101

Master these few basic color correction steps, and you are well on your way in the art of Color Correction. This is just the beginning of what you can accomplish with the robust Color Correction 3-Way tool. We suggest you review the article on reading video scopes, and watch for next month's focus on secondary color-correction filters.

Contributing editor Morgan Paar is a nomadic producer, shooter and editor, currently teaching high school video production.

Tags:  August 2008
Morgan
Paar
Fri, 08/01/2008 - 12:00am