SMART III measures the intensity of the three primary colors using test images and shows the results in several types of graphs. In particular, SMART uses the Avia disc to display a series of images in which windows appear in the center of the screen, against a black background, that represent black and white and various shades of gray in linear steps of 10 IRE units. (IRE is term use to represent the video input voltage level with black represented by IRE 0, and white by IRE 100.) With each of these IRE windows, SMART uses the light meter and colored filters to measure the light intensity of each of the primary colors at each IRE level as shown above.

Grayscale Tracking
The color balance of the projector at various light intensity levels determines the quality of what is called ‘grayscale tracking’. The idea is that black, white, and all shades of gray, should have the correct ratio of the three primary colors used in video projection, Red, Green and Blue.

Projectors meant for HT usage, typically make white by shining just the right proportion of red green and blue light on the screen. Ideally shades of gray should have the same proportion of red, green and blue as white, but less of each color. What’s important is that this RGB ratio be the ‘correct’ ratio, and that this ratio remains constant as the intensity of the light in the image changes. This ability for the color balance to track properly with the different levels of light intensity is therefore what is called ‘grayscale tracking’.

Why is Grayscale tracking so important? Well, imagine watching a black and white movie on your color projector. Ideally whites should look white, blacks should look black and all the shades of gray should look, well gray. If the projector in the darker part of the image, used too much green, the shadows would seem a bit greenish, and that would be distracting. If the highlights looked yellow, that would also be distracting. So, it is important that all light intensity levels of ‘gray’ have the same ratio of all three colors to achieve a good black and white image on a color projector. Grayscale tracking is also important with color images, as one does not want the color of an object to change as the level of illumination changes, or is in a shadow. Good grayscale tracking, however, requires careful calibration – typically beyond that done by the manufacturer or easily done by a user without test equipment. That is where SMART III comes in.

To read more about SMART click on one of the topics below.

SMART and Grayscale tracking/Color Balance

SMART and Gamma Tracking