Projector bulb brightness

[robfisher]

There seems to be a lot less information on the web about projectors than there is about cameras, so I thought I would try my question here.

Which is brighter: A 125V 150W bulb, or a 12V 100W bulb?

I suppose it comes down to whether the current or the power is important - the former bulb would draw 1.2A, the latter 8.3A, perhaps making it brighter. I am sure there may be other considerations too, like what type of bulb is used.

In general, what is considered a bright projector, and how bright does the bulb need to be to fill a given size screen?

It seems silly to have a big, expensive camera, and then not see the film at its best when it's projected - so any wisdom on this topic anyone here has would be greatly appreciated!

Thanks,
Rob.

[#Pedro]

Hi Rob!
Wow, you REALLY have courage to post such a topic in our all-video-and-nothing-else world! I always have asked me, why people do film in Super 8 which much efforts, equipment that costs the price of a second hand car, and over $10 per 2,5 minutes of film - if they reduce all that brilliant quality to the "ugly" video screen, instead of shooting directly with a video system.

To comment your question:
The brightness of a conventional screening don?t only depend on the power consumption of the lamp, it depends also on how the bright spot of the lamp combines with the frame size of the film. And the spot diameter of the lamp depends mostly on the feeding voltage. For S8 you can achieve the brightest results with a 15V / 150W halogen lamp, suitable for screens up to 2 meters, supposing a lens with 1:1,3 or better. Forget projectors with 12 V/100 W or 8 V/50 W bulbs. They are only for small home screens of 1,25 meters or smaller.
High voltage bulbs (125 V, 220 V) require a condensor lens system to reduce the diameter of the spot and to focus it to the film frame.
A halogen bulb with cool light reflector is much better.

For larger screenings or quality home screenings with a less yellowish light it?s best to use projectors with a high power bulb (xenon). They are suitable for screeings up to 10 meters. There are xenon bulbs 250 W and 270 W for S8 around. Special projector models of Elmo and Beaulieu use them. But you can update nearly every high-end S8 Projector with a standard 15V/150W bulb to that system. At Wittners there is a update set which contains the power feed and the switch-on circuit for the lamp for about $500 and the bulb itself for about $200. To convert a standard projector, you must apply an additional fan to it?s lamp house.

For 16 mm the best halogen bulb is 24V/250W, to illuminate the larger frame size. And at Wittner?s you will find an xenon set for 16 mm, too. (http://www.wittner-kinotechnik.de/)

Pedro

[robfisher]

Thanks, Pedro, for your detailed answer! Sorry to any video people offended by my heresy - I just like to project my film the old fashioned way!