Rear Projection advice
January 24, 2012 8:16 AM Subscribe
Rear projection gurus, advise me.
I have a short film in mind to be shot using rear projection. I need to acquire a projector, screen and data source. Willing to spend between $1000 - $1500. I've shot rear projection before, on film, with a rental screen and projector but this short is going to take a while to make so I need a somewhat long-term setup.
THE MOVIE:
Black and white, shot on 5D, can be relatively noisy so I don't need crazy bright rear projection. Will be able to shoot in an all black environment, front elements will be lit mostly by candle-light so shouldn't destroy the screen contrast too much. Shooting some miniature exteriors that may require a little lighting. But in general the movie is quite dark, foreground wise.
THE SCREEN:
Film aspect ratio will be 16x9 and the screen will need to cover a MCU 2 shot and OTS dialog, so I'm guessing the screen needs to be at least 8' x 4.5'. Does that sound right or am I thinking too small? I'm willing to build a frame if the stuff that comes on rolls would work. Is that stuff any good or should I buy an actual screen? Any recommendations?
THE PROJECTOR:
Full HD 1080p if possible but 720p probably OK, HDMI or DVI in I suppose. How many lumens should I be looking at? Since it's B&W I mostly care about good contrast. Any suggestions?
THE DATA SOURCE:
1080p source material for the projections. I have a computer I could run it off but that seems kind of clunky, I do have an xBox that I could use... was thinking about using that since it would be pretty portable. I don't mind installing Linux on it as I never use it. I'd rather save the money here and put most of it into 1) the projector and 2) the screen.
Any other advice?
I have a short film in mind to be shot using rear projection. I need to acquire a projector, screen and data source. Willing to spend between $1000 - $1500. I've shot rear projection before, on film, with a rental screen and projector but this short is going to take a while to make so I need a somewhat long-term setup.
THE MOVIE:
Black and white, shot on 5D, can be relatively noisy so I don't need crazy bright rear projection. Will be able to shoot in an all black environment, front elements will be lit mostly by candle-light so shouldn't destroy the screen contrast too much. Shooting some miniature exteriors that may require a little lighting. But in general the movie is quite dark, foreground wise.
THE SCREEN:
Film aspect ratio will be 16x9 and the screen will need to cover a MCU 2 shot and OTS dialog, so I'm guessing the screen needs to be at least 8' x 4.5'. Does that sound right or am I thinking too small? I'm willing to build a frame if the stuff that comes on rolls would work. Is that stuff any good or should I buy an actual screen? Any recommendations?
THE PROJECTOR:
Full HD 1080p if possible but 720p probably OK, HDMI or DVI in I suppose. How many lumens should I be looking at? Since it's B&W I mostly care about good contrast. Any suggestions?
THE DATA SOURCE:
1080p source material for the projections. I have a computer I could run it off but that seems kind of clunky, I do have an xBox that I could use... was thinking about using that since it would be pretty portable. I don't mind installing Linux on it as I never use it. I'd rather save the money here and put most of it into 1) the projector and 2) the screen.
Any other advice?
Response by poster: I'll be setting up in my windowless basement, so probably around 10 feet of space between the screen and projector would leave me enough room on the other side to do what I need to do.
posted by nathancaswell at 3:19 PM on January 24, 2012
posted by nathancaswell at 3:19 PM on January 24, 2012
Okay, no real gurus have emerged yet, so I'll talk and maybe it'll help.
The further your subject is from the screen, the easier it is to light the subject without lighting the screen, but the larger your screen needs to be. The larger your screen is, the dimmer it will be. The longer the lens you shoot with, the smaller your screen needs to be for a given distance, and the further back it can be for a given size. So I'd try to shoot with the longest lens that would fit in the basement.
Let's say your medium close up is 4 feet across, and your screen is 8. Then your actor needs to be half the distance from the camera as the screen is.
If you shoot it with a 100mm lens, that's a 20 degree field of view. (Maybe fewer degrees if Canon 5D's video mode doesn't use the full frame but I'm estimating) (Calculations from here) So with that lens, your camera is 11 feet from the actor and 22 from the screen. If you have only 10 feet to throw an 8 foot image, you want a projector with a throw ratio D/W of 1.25 or lower.
Now let's say the lighting on the actor is 3 feet from the actor and 14 feet from the screen. Lighting is inverse-square to distance, so the screen will receive (3*3)/(14*14) about 4.5% as much light as the actor, which sounds acceptable to me. Let's say your light that's 3 feet from your actor is a literal candle, so one candela, which is roughly 12.6 lumens. A 3 foot sphere has a surface area of about 28 square feet. An 8x4.5 foot screen is 18.5 square feet. So to light your screen as brightly as the actor you'd need only a 19 lumen projector, which isn't much at all. (Let's maybe make it 40 lumens, if we assume we lose half the light bouncing off the screen.)
Of course, lighting with a single candle is incredibly dim, especially if you're using a long lens.
Suppose we go the other way, and presume you use a 1700 Lumen projector. You lose half going through the screen, 850, then *28 and /18.5 that means your "candle" can be 1286 Lumens.
I welcome anyone to point out what I got wrong, I was making a lot of this up as I went along, and I could have missed something important.
posted by RobotHero at 9:42 PM on January 25, 2012
The further your subject is from the screen, the easier it is to light the subject without lighting the screen, but the larger your screen needs to be. The larger your screen is, the dimmer it will be. The longer the lens you shoot with, the smaller your screen needs to be for a given distance, and the further back it can be for a given size. So I'd try to shoot with the longest lens that would fit in the basement.
Let's say your medium close up is 4 feet across, and your screen is 8. Then your actor needs to be half the distance from the camera as the screen is.
If you shoot it with a 100mm lens, that's a 20 degree field of view. (Maybe fewer degrees if Canon 5D's video mode doesn't use the full frame but I'm estimating) (Calculations from here) So with that lens, your camera is 11 feet from the actor and 22 from the screen. If you have only 10 feet to throw an 8 foot image, you want a projector with a throw ratio D/W of 1.25 or lower.
Now let's say the lighting on the actor is 3 feet from the actor and 14 feet from the screen. Lighting is inverse-square to distance, so the screen will receive (3*3)/(14*14) about 4.5% as much light as the actor, which sounds acceptable to me. Let's say your light that's 3 feet from your actor is a literal candle, so one candela, which is roughly 12.6 lumens. A 3 foot sphere has a surface area of about 28 square feet. An 8x4.5 foot screen is 18.5 square feet. So to light your screen as brightly as the actor you'd need only a 19 lumen projector, which isn't much at all. (Let's maybe make it 40 lumens, if we assume we lose half the light bouncing off the screen.)
Of course, lighting with a single candle is incredibly dim, especially if you're using a long lens.
Suppose we go the other way, and presume you use a 1700 Lumen projector. You lose half going through the screen, 850, then *28 and /18.5 that means your "candle" can be 1286 Lumens.
I welcome anyone to point out what I got wrong, I was making a lot of this up as I went along, and I could have missed something important.
posted by RobotHero at 9:42 PM on January 25, 2012
This thread is closed to new comments.
posted by RobotHero at 1:32 PM on January 24, 2012