16 April 2013 by Shifali Rao
Contrast ratio is essentially the difference between the deepest black and the purest white your projector displays. So, if this ratio is higher you get richer blacks giving more scope for better detail.
However, it isn't always advisable to compare contrast ratios while buying a projector since manufacturers use varying methods for calculation, so it's as pointless as comparing apples to oranges. So if you see a 600:1 on projector A and 2000: 1 on projector B, it doesn't necessarily mean B has greater contrast than A.
Contrast ratio is typically calculated by measuring the amount light output of the black versus the light output for the whites displayed by your projector. However, there's two slightly disparate standards used to measure contrast ratios of a projector :Full on/Full off and ANSI contrast ratios which can't be compared.
ANSI contrast ratio is measured with a checkerboard of 8 black and 8 white rectangles. The contrast is gathered by measuring the average light output of all the white checks, and the average light output of all the black ones. ANSI contrast ratio is a ratio of the two averages obtained. The ANSI values represent a more realistic contrast since it includes some margin for ambient light.
With the Full on/ Full off method the ratio obtained is more ideal than realistic since the white and black light output are not measured simultaneously, and the blackness measure is the "full off" value in ideal conditions in a pitch black room. Using test cards for measurement, the "full on" state is the brightness measurement of a white (100 IRE) test pattern; and the "full off" is the measurement on a black (0 IRE) test pattern. This type of calculation results in almost no reading in the "full off" measurement.
Furthermore the thing about contrast ratios is that even the difference between 400:1 and 2000:1 is hardly noticeable in bright rooms. Ambient light tends to diminish the effect of contrast, so higher contrast ratios are more apt for cinema and movie buffs where the projector is placed in a darkish room.
This selection of the best projectors is narrowed down to the top rated models which have contrast ratios of 2000:1. However you need to ascertain that this is the ANSI contrast. A high contrast of 2000:1 is necessary if you need the projector for a home theatre because movies require high contrast. Typically 1500: 1 is claimed to be pretty good so anything higher than that is quite exceptional for watching HD movies where cinematic details are much appreciated.