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Shooting a projector (DLP? LCD?)

projector LCD DLP

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#1 Michael Ognisanti

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Posted 23 April 2017 - 10:49 AM

Hello,

 

I have a commercial shoot coming up where our actor will be next to a projector pointing at charts and graphs.  I have questions about shooting the projector.  Here they are...

 

Is their a specific type of projector that would be better to shoot?  DLP? LCD LED?  Should I get the brightest option? What would that be?

 

If I'm exposing for the projector would that require more output from our production lights?  We are in a high rise office building with an open floor plan and fluorescent overheads.  We are limited to house power.  We will mostly use Kinos and maybe small HMI's?

 

What about color balance?  Are the projectors daylight? and can I change them if need be?  I am already dealing with the fluorescents and since It's a large space I doubt we will be able to swap out with balanced tubes.

 

Finally, do I need to be concerned about flickering or rolling bars like with a computer monitor?

 

Thanks in advance for your help!

 

Michael

 

 


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#2 Stephen Baldassarre

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Posted 23 April 2017 - 07:30 PM

DLPs tend to flicker more (especially single-chip projectors) since they work by rapidly oscillating tiny mirrors.  Single-chip projectors have color wheels to filter the light so colored strobing can occur.  LED, while often not as sharp, do better when rephotographed for that reason.  Most projectors use tungsten/halogen lamps so it will look yellow if your are white balanced to fluorescent overhead lighting.  You may be able to electronically balance the projector to FL lighting but most don't have sufficient wiggle room.  Your best bet is to balance the FLs to match the projector via gels or see if you can get a filter to match the projector's light to the FLs.

 

Really though, your biggest problem is going to be getting the projected image bright enough and avoiding spill on the screen, which washes out the shadows.  If you're using rear projection, you can put an ND filter over the screen to reduce the wash.  What happens is, even though you may loose two stops of light from the projection, ambient light passes through the filter twice and is thus attenuated four stops.


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#3 Michael Ognisanti

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Posted 24 April 2017 - 11:03 AM

DLPs tend to flicker more (especially single-chip projectors) since they work by rapidly oscillating tiny mirrors.  Single-chip projectors have color wheels to filter the light so colored strobing can occur.  LED, while often not as sharp, do better when rephotographed for that reason.  Most projectors use tungsten/halogen lamps so it will look yellow if your are white balanced to fluorescent overhead lighting.  You may be able to electronically balance the projector to FL lighting but most don't have sufficient wiggle room.  Your best bet is to balance the FLs to match the projector via gels or see if you can get a filter to match the projector's light to the FLs.

 

Really though, your biggest problem is going to be getting the projected image bright enough and avoiding spill on the screen, which washes out the shadows.  If you're using rear projection, you can put an ND filter over the screen to reduce the wash.  What happens is, even though you may loose two stops of light from the projection, ambient light passes through the filter twice and is thus attenuated four stops.

Thanks Stephen!

 

It seems like rear projection would be best than?  Would rear projection be better to fight against spill?  Or is it the same as front?  I could also use front projection LED and throw some gel over that to get the color balance to match.  It sounds like I would lose more output that way though.  Thanks again


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#4 Tyler Purcell

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Posted 24 April 2017 - 11:30 AM

Single chip DLP's won't work at all, as Stephen pointed out, the color wheel makes a rainbow pattern on anything shot with them. 3 Chip DLP's are what they use for rear projection in movies today, so they work totally fine. If you can rent/borrow a 3 chip DLP projector, you'd be totally fine. However, due to cost, I'd just get a 3 chip LCD projector, they have zero issues.

Most higher end projectors have white balance adjustments, I know my little cheap one does and it works great. So getting the level of white close to outdoor color temp, may not be a problem. I haven't tested it, but I bet it would work fine. If you have a cinema camera, you should be able to select the proper shutter angle to get rid of any potential flicker or bar, but I don't think there will be any.

Since you'll be shooting indoors, you can probably get away with 5000 lumens with a room that's lit. Since you don't need a cinema-grade projector, you can get away with an office one, no problem.
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#5 Michael Ognisanti

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Posted 24 April 2017 - 11:34 AM

Single chip DLP's won't work at all, as Stephen pointed out, the color wheel makes a rainbow pattern on anything shot with them. 3 Chip DLP's are what they use for rear projection in movies today, so they work totally fine. If you can rent/borrow a 3 chip DLP projector, you'd be totally fine. However, due to cost, I'd just get a 3 chip LCD projector, they have zero issues.

Most higher end projectors have white balance adjustments, I know my little cheap one does and it works great. So getting the level of white close to outdoor color temp, may not be a problem. I haven't tested it, but I bet it would work fine. If you have a cinema camera, you should be able to select the proper shutter angle to get rid of any potential flicker or bar, but I don't think there will be any.

Since you'll be shooting indoors, you can probably get away with 5000 lumens with a room that's lit. Since you don't need a cinema-grade projector, you can get away with an office one, no problem.

Thanks Tyler,

 

We are using an Alexa Mini so tweaking the shutter should be fine.  I'll look for one with white balance adjustments.  Appreciate all the great info guys!


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#6 Stephen Baldassarre

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Posted 24 April 2017 - 12:13 PM

It seems like rear projection would be best than?  Would rear projection be better to fight against spill?  Or is it the same as front?

Front and rear projection are the same as far as spill is concerned.  The advantage of rear projections is solely because you can put ND gels over the viewing side of the screen, which reduces light output but reduces spill by twice as much.  The best thing to do is simply keep spill off of the screen as much as possible.

Another option, if you use a glass (retroreflective) projection screen, is to project into a mirror (at 45 degree angle) directly under the camera lens.  That greatly increases the brightness of the image from the screen but you are stuck with shooting from only one position.


Edited by Stephen Baldassarre, 24 April 2017 - 12:14 PM.

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