The DLP Rainbow Effect: What Causes It and Who Sees It

A single-chip DLP projector has one array of micromirrors and one light path. To make a colour image it shows the red component, then the green, then the blue, in rapid sequence, filtered either by a spinning colour wheel in front of a lamp or laser-phosphor source, or by strobing separate coloured LEDs or lasers. Your visual system is supposed to integrate the sequence into one colour image, and usually it does.

Three-chip designs do not have the problem because they do not have the sequence. A 3LCD projector splits white light into red, green and blue paths, modulates each with its own panel, and recombines them — all three colours are on screen simultaneously. The same is true of the three-panel LCoS designs JVC and Sony use. No sequence, no artifact.

Sensitivity varies between people and is not something you can train away. Estimates of the affected proportion vary, but every account agrees it is a minority and that within that minority the range runs from 'noticeable once and then forgotten' to 'unwatchable'. It is not correlated with visual acuity or with being fussy about picture quality.

It shows up most on high-contrast content: white credits on black, a streetlight in a night scene, a bright reflection. It is worse when your eye moves across the image rather than tracking one object, and worse in a dark room where the contrast between the bright object and its surroundings is highest.

Speed. A faster colour wheel, or a faster LED or laser strobe rate, shortens each colour's dwell time and narrows the separation. Cheaper projectors historically used slower wheels with fewer segments; current designs run faster ones, and the LED and RGB-laser DLP models in this catalog switch far faster than any mechanical wheel can spin. That is a real improvement, and it does not eliminate the mechanism.

Higher frame rates help for the same reason, which is why the question of whether a 120 Hz signal reduces rainbows comes up so often. More refreshes per second means more, shorter colour sub-frames, so the artifact is less likely to be perceived — but a viewer who is strongly sensitive will still catch it. It is a reduction, not a fix.

Watch a single-chip DLP projector, in a dark room, on content with bright objects against black, for at least twenty minutes, and move your eyes around the image deliberately. A demo room at a dealer, a friend's projector, or a returnable purchase all work. Twenty minutes of a bright daytime scene proves nothing.

If you turn out to be sensitive, the fix is a technology change, not a model change: this catalog's 3LCD, D-ILA and SXRD projectors are immune by construction. If you are not sensitive, single-chip DLP gets you the sharpest pixel structure and the lowest input lag in the category, and none of this matters to you at all.