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10,000 lumens can't be wrong


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#1 Alessandro Machi

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Posted 16 September 2007 - 04:37 PM

I had a chance to check out two film festivals this weekend. Both projected digitally.

One place was using a 5000 lumens projector and the image didn't pop off the screen.
It wasn't horribly bad, it was kind of OK, but a bit dim. The other place also seemed to have some projection issues as well. Contrast seemed off, darker shots were too dark as well.

Any comments or experiences on what the minimum acceptable lumens is for big screen digital projection? I can't give a specific to the size of the screen but lets assume the theatre seats at least 500 people. Perhaps between 500-750.

I would surmise that 10,000 lumens would be the minimum and that perhaps festivals get caught in renting the 5,000 lumen version because the price is too good to pass up.

Also, these menu driven projectors, they can make the audience giggle between movies when a menu screen suddenly pops up and a little cursor is seen chasing down the right menu item and then trying to make an adjustement as quickly as possible.

Menu driven choices for real time events is something invented by Satan.
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#2 Robert Hughes

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Posted 17 September 2007 - 09:37 AM

A 5000 lumen projector is no great shakes nowadays, about what you'd see in use for a corporate Powerpoint presentation to 100-200 people on a 7.5x10' screen. For 500 - 1000 people I'd recommend using 12x16 or larger screen with a 10K Christie at least, perhaps double-stacked. But as you say, the price goes up ever more steeply the larger and brighter you go. A Christie rents for about $3000 a day.

Keep the ambient light level in your theater to an acceptable minimum. I assume you're doing this presentation indoors? Otherwise, if you're outdoors you'll need bigger screens and more powerful projectors to cut through the ambient light of the surrounding neighborhood. It gets expensive and complicated - outdoors you'll probably need to talk to a professional A/V company to supply the equipment and services. Think $20K rental for a big outdoor event projection setup.

As for the menus popping up, that's probably because the operator didn't know what he was doing or didn't have proper switching equipment. Some projectors go into menu mode when they lose a video signal (as when somebody is moving the VGA cable from one machine to another). Again, the video switch and ancillary gear costs money, so I'm not surprised the local no-cash filmfest had problems.

Edited by Robert Hughes, 17 September 2007 - 09:40 AM.

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#3 Alessandro Machi

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Posted 17 September 2007 - 07:30 PM

A 5000 lumen projector is no great shakes nowadays, about what you'd see in use for a corporate Powerpoint presentation to 100-200 people on a 7.5x10' screen. For 500 - 1000 people I'd recommend using 12x16 or larger screen with a 10K Christie at least, perhaps double-stacked. But as you say, the price goes up ever more steeply the larger and brighter you go. A Christie rents for about $3000 a day.

Keep the ambient light level in your theater to an acceptable minimum.....


$3,000 dollars a day for a 10K lumens projector!!! Ouch!

I didn't know that double stacking was going on until the projectionist mentioned it to me this past weekend. They weren't doing a double stack however.

I'd suggest zooming the image in a bit and make it smaller and brighter. Not all the way in but zooming in a porportion can make a difference. Betacam SP was one of the playback sources and using the betacam sp deck with the video levels and color raised might have helped, but that was not tried. I offered to loan them a proc amp so they could access the proc amp capability of the UVW-1800.

It's possible that a PVW betacam sp deck with the built in proc amp controls might boost the signal enough to make a 5000 lumens projector look like a 10000 lumens projector???

There was also a reflection bouncing from the screen to the glossly floor below and that definitely made the picture look dimmer (as you stated above). If they could have afforded a huge piece of duvetene for the floor that would have made the picture appear a bit brighter.
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#4 Phil Connolly

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Posted 19 September 2007 - 11:02 AM

It's possible that a PVW betacam sp deck with the built in proc amp controls might boost the signal enough to make a 5000 lumens projector look like a 10000 lumens projector???


Erm no, it can't magically make the lamp on the projector any brighter and would probably just result in white clipping at best, and sync issues at worst, a projectors input is designed to take a signal at a certain level, feeding it with an illegal signal can only create unpredictable results.
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#5 Michel Hafner

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Posted 20 September 2007 - 09:10 AM

You have to know the size of the screen then you can compute the foot lamberts for top white. If it's not 12 to 16 but less it's substandard.
Whether an image pops or not also depends on how it was shot/graded, how much the room is also a projector (by reflections and ambient light sources) and what the contrast of the projector is (ANSI and On-Off). Some type of images never pop in commercial cinemas since the necessary contrast is unattainable from the projector and room, unlike the situation in light controlled home cinemas where you can make any image pop (if it's graded that way) with the 'right' equipment.
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#6 Alessandro Machi

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Posted 21 September 2007 - 05:02 AM

Erm no, it can't magically make the lamp on the projector any brighter and would probably just result in white clipping at best, and sync issues at worst, a projectors input is designed to take a signal at a certain level, feeding it with an illegal signal can only create unpredictable results.


I have had the experience of adjusting the settings on a betacam sp video deck that was the source machine for a video projected image. I watched the screen get significantly brighter as I raised the video level setting on the betacam sp deck and I also slightly raised the set-up video level as well.

Of course I then had to add chroma saturation back to the picture. I don't know the overall lumens value that was added but it was significant. White Clipping can definitely be an issue but if the video image was originally mastered using 100 IRE and 0 black as original guidelines, the video signal could easily be raised to 110-115 IRE (which would also include raising the set-up to 7.5 black plus added chroma saturation) without any video clipping.
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#7 Alessandro Machi

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Posted 07 October 2007 - 01:21 AM

I went to the Tarfest film festival today. The final film shown just popped off the screen. At first I thought it was betacam sp camera origination, then I realized it was 35mm, then when the more subtly lit scenes seemed to have this magnificent quality to them, I really began to wonder what I was seeing. It was Super-35.

Amazing how film sort of does itself in by being so good. Probably most people there probably thought the film short was shot on digital. Projection was done on a regular DVD with a line doubler. Wow.

What is interesting to me is because it was film origination it actually helped to make the dvd projection look better than it really was. The lower lit scenes still had magnificent highlights throughout and it made me realize that digital projection is actually helped by projecting film originated material. Clearly the lower lit scenes could have been slightly brightened during projection but they still held together magnificently.

The clamor to change to digital projection should not be the end of film because if something is shot on film and optimized for digital projection, I think it would actually allow for a theatre to go with a cheaper projection system with no need to ever upgrade.

Unfortunately, the digital crowd will also try and equate digital projection with the death of film when it is film that actually makes the digital projection look better than it really is.
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