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Topic: Drive in Theatres with Anamorphic Lens On Digital
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 01-05-2015 06:31 AM
In theory, the light from a 4K projector should be greater than the light from the same 2K projector due to the larger aperture of the 4K projector (1.38" versus 1.2"). There are mitigating circumstances that keeps one from making a direct correlation though. Just because the imager is larger does not mean that the efficiencies of the optics are equivalent on both. And continuing in that line, the lens. Most zoom lenses are more efficient towards the shorter end of the range so if the same lens is used for 2K and 4K, it is likely to be a little more efficient for the 2K. However, if you are kicked into another lens size then all bets are off. I have theatres where the "same" projector is used on two auditoriums have the same size screen but due to the throw, the lenses are different...the resulting light on the screen varied rather greatly. I've found that the lenses in the middle of the lens line tend to be more efficient than those on the opposite extremes. The 1.2-1.8 lenses, for instance are typically not as efficient as a 1.4-2.05 lens in any particular manufacturer. The 2.4-3.9 also can be a light hog.
However, with an anamorphic, you can bank on the 23% light gain for scope.
In a Drive-In, one is normally so far back from the screen and the screen "quality" (they are normally quite nasty looking up close), that 4K is probably lost in such an application.
I'm curious to see your numbers on the 16% light improvement...to really claim it, you'd need to shoot the same size screen/throw (use the same lens) to really measure the light improvement. The screen reflectivity would need to be measured too to eliminate its contribution. With an anamorphic, it is much easier to quantify...you use the same equipment and merely measure with and without the anamorphic (presuming the prime lens can zoom to both extremes).
As for costs, another brand of DLP projector plus the anamorphic would be 35% more efficient than the 2K NEC on Scope. They would have more light with a 4000-4500 watt lamp than your 4K NEC with a 6K lamp. It would be less expensive to buy and less expensive to operate every day of its existence.
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Frank Angel
Film God
Posts: 5305
From: Brooklyn NY USA
Registered: Dec 1999
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posted 01-05-2015 09:07 AM
quote: Mark Gulbrandsen
I have measured typically 16% more light from a 4k vs. an equivalent 2K model.
That may be (or not so much, considering Steve's points), BUT, practically speaking, that works only when considering coverting from film and making decisions about which way to go with a digital install; for the guys who already purchased their 2K equipment, it's very unlikely that they are going to switch out to 4K anytime soon. And given the economics of DIs, especially those not runing 365, if they didn't go the anamorphic route from day one, they probably are going to live with what they've got, knowing the cost of those lenses.
I take it "prime" lenses are not manufactured in incrimental steps like film lenses, yes? So it's not like a prime lens can be selected which is the most efficient optical "sweet" spot for a given throw, and then use an anamorphic adapter for scope. With those typically very long DI throws, they would still be using a zoom lens set at an extreme point that may not be the most efficient. Which again points to the fact that NOT requiring fixed prime lenses and anamorphics was a compromise that shouldn't have been DCI approved. ESPECIALLY since everyone should have learned by now the cropping/extra magnification mistake that was made with the 1.85 film format.
Back then, instead going with two different prime lens and one anamorphic, it could easily have gone with a single prime lenses and two different anamporhics and a full frame height for both, ala, Glenn Berggren's proposal (at Schneider? I think). If they had gone that route, no doubt in short order lens manufactures would have been able to greatly improve the variable anamorphic to be very efficient, which would allow motorizing them for automation and then they wouldn't have even needed two different anamorphics in a turret.
Compromise, compromise...all is compromise.
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