|Originally posted by djbluemax1
Pretty simple. On/off CR is the greatest difference in lumen levels from a fully white image and a fully black image. (literally as bright as the projector can go to as dark as it can go).
Just wanted to clarify a couple of things. The on/off CR that most of us care about and discuss around here is calibrated. So, not the brightest the projector could go if colors where blown out. Some manufacturers do a better job of specing with a home theater setup than others. JVC even exceeds their CR spec for the HD2K at d65. Also, magazines and many of us measure 100 IRE to 0 IRE with video signals (some room for above white), so this can also affect the numbers and means that it often isn't even as bright as the projector could go at d65.
And nobody with a multi-position iris specs on/off as the brightest the projector can go with the iris open and the dimmest it can go with the iris closed unless it is dynamic. The brightest to dimmest would be pretty much irrelevant if that can't do it during movies without intervention and they would get trashed for that. The ratio between the brightest that the Sharp 12k can go with bulb on high and brightest iris choice is probably 15k:1 or so to the dimmest, but it is speced at 5500:1 because it can't do that other range without changing settings.
But the basic point is the same.