Color-correct Your Video in IMovie
Today's cameras make it easier than ever for shooters to get good-quality footage, but sometimes the camera misreads the brightness or color balance, or the environment's lighting introduces a color tint.
iMovie '09 ( Macworld rated 4 out of 5 mice ) (and iMovie '08) can help you correct your footage without turning to advanced tools like Apple's professional Color ( Macworld rated 3.5 out of 5 mice ) application. iMovie doesn't offer the same level of control or quality, but it works well for fixing common issues.
To access these features, select a clip in either the Project Browser or the Event Browser and press the V key. You can also click the Action menu (the button with a gear icon in the lower-left corner of a clip when your mouse pointer is over it) and choose Video Adjustments. The Inspector appears with the Video tab selected.
To make a scene brighter or darker, a few options are available. Drag the Exposure slider to increase or decrease the values of the highlights and shadows. Drag the Brightness slider to adjust the overall light level.
I prefer to use the Levels adjustments in the histogram at the top of the Inspector. In Figure 1 below, the histogram reveals that the video's drab appearance is due to a lack of whites: the colors drop down to zero well before the right edge of the histogram, which represents the whitest value in the color spectrum. To correct this, drag the rightmost level slider so that the colors move to the right edge of the histogram. That redefines which values are the brightest in the image. (The same technique applies to darks, using the other slider.)
Adjust the white point
A room's lighting can often confuse a camcorder into using the wrong value for what it perceives as white, which can lead to video with an unwanted orange or green hue. An easy way to compensate is to adjust the white point: you tell iMovie which color is supposed to be white, and it modifies the rest of the colors to compensate. This feature can also help bring warmth to a cool scene, or vice-versa.
With the Video Inspector visible, position your pointer to an area of a selected clip's image that should be white and click the button (see Figure 2 below). Or, drag within the color wheel in the White Point section of the Inspector to modify the image's appearance.
If necessary, modify the Gain sliders to adjust for any other color casts that remain; these controls appear in the inspector only when the Show Advanced Tools option is enabled in iMovie's preferences.
With these and other video adjustments, it's important to note that the clip's icon doesn't reflect the changes you make (but it does gain an icon to indicate that it has been edited). The footage in the Viewer does reflect the adjustments.
Jeff Carlson is the author of iMovie '09 & iDVD for Mac OS X: Visual QuickStart Guide (Peachpit Press; 2009) and the managing editor of TidBits.