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Rear Projection, rolling shutter, any issues?


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#1 Greg Ephraim

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Posted 10 February 2009 - 03:48 PM

Hey All,

Got a music video coming up where we want to shoot some rear projection, but it doesnt have to be perfect, going for a more corny look....but was wondering if there is any issue with the RED with rear projection with the rolling shutter. Are there projectors that are better for the job than others, any help would be greatly appreciated, this is my first time giving rear projection a shot. (what would be a good lumens amount, does it make a difference between LCD or DLP projection, etc...)

Thanks in advance for any help!

Cheers
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#2 Keith Walters

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Posted 10 February 2009 - 08:38 PM

Hey All,

Got a music video coming up where we want to shoot some rear projection, but it doesnt have to be perfect, going for a more corny look....but was wondering if there is any issue with the RED with rear projection with the rolling shutter. Are there projectors that are better for the job than others, any help would be greatly appreciated, this is my first time giving rear projection a shot. (what would be a good lumens amount, does it make a difference between LCD or DLP projection, etc...)

Thanks in advance for any help!

Cheers

Steer clear of DLP at all costs!
LCD is a the only real choice for anything requiring in-shot video display, because both full-size LCD TV screens and the 35mm-slide-sized LCD light modulators in LCD projectors behave like a colour transparency. There is no stobing or any other sort of brightness pulsation. You can shoot at any frame rate you choose, and the image will still look like you are filming a picture printed on paper.

Most lower-cost DLP projectors have only a single DLP light modulator and project the red, green and blue images sequentially through a rotating colour filter wheel. It is normally done at a fast enough rate so that to the viewer, it looks like a continuous full-colour image. However, it won't look like that to most cameras!

As for the brightness required, that obviously depends on how large an image you are going to project, what ASA you want to run the camera at and so on. You basically should get the brightest projector that your budget can support, and adjust the lighting of everything else to match. This can be tricky, because you have to keep as much light as possible off the projection screen if you don't want it to be obvious that you are using rear projection..
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#3 Michael Collier

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Posted 10 February 2009 - 09:14 PM

When shooting an LCD projected image, it is important to note the grid of pixels can create a moire pattern. You might need to defocus the projector lens a tad to keep this from happening (also simply staging action away from the screen will naturally soften the background, and give you more room to light, but will increase the size of screen required.)
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#4 Keith Walters

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Posted 10 February 2009 - 10:06 PM

When shooting an LCD projected image, it is important to note the grid of pixels can create a moire pattern. You might need to defocus the projector lens a tad to keep this from happening (also simply staging action away from the screen will naturally soften the background, and give you more room to light, but will increase the size of screen required.)

Excellent point. To date I've only had experience with shooting things like that on film, never thought about the moire issue and I've certainly seen what happens when you try to photograph an LCD TV with a digital camera!
Fortunately, that will be immediately obvious on your monitor or even in the viewfinder and easily fixed as you say.
Obviously the more resolution the projector has, the better, but the background being slightly out of focus is probably going to look more normal anyway.
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#5 Greg Ephraim

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Posted 11 February 2009 - 02:28 AM

Excellent point. To date I've only had experience with shooting things like that on film, never thought about the moire issue and I've certainly seen what happens when you try to photograph an LCD TV with a digital camera!
Fortunately, that will be immediately obvious on your monitor or even in the viewfinder and easily fixed as you say.
Obviously the more resolution the projector has, the better, but the background being slightly out of focus is probably going to look more normal anyway.



awesome! thanks for the fast responses guys! LCD it is, and I was thinking about having the projected image out of focus a bit, so that will work out perfect!
if anyone can think of any other tips, of course I would greatly appreciate it!
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