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Image Projection

Discussion in 'Multimedia, Projection, and Show Control' started by jonliles, Sep 24, 2008.

  1. jonliles

    jonliles Active Member Fight Leukemia

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    I am not sure if this topic would fall under lights or under FX, but what the heck.

    I am currently designing and hanging a "dance show" for my daughters HS. This years Song and dance theme is "Planes, trains, and Automobiles" (think 60's). The the lights are your typical modified McCandless warm cool mixture with strong back/top light (and a few side lights - limited places to hang).

    We are hanging a drop in the back to project images in theme with the music. I am truly hoping to do this by rear projection (ie: kid running laptop and powerpoint). My concern is that the images would be washed out by the washes. I've done this in small black boxes with varying degree of successes.

    Does anyone have experience with video / image projection in LOW budget venues?
     
  2. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    Neither! Moving this thread to the Multimedia and Projection forum.

    Sounds like you have the media, control, and projector handled, so search in this forum for screen material ideas. You really should use official RP screen material, but as long as it's less than a two-week run, I've spliced it before with good quality 2" cello tape, rather than the stupidly expensive screen tape, or having a custom screen made. Some have even reported success using a shower curtain liner. Whatever material, it needs a well-built frame on all four sides to staple the screen onto, just like covering a flat.

    What size of screen are we thinking? A local AV company (I'd start by sending a private message to CB member Oldschool) may give you a good deal on the rental for a fast-fold screen with RP surface, but you'll be limited to their stock sizes: 9x12', 10.5x14', 15x20' for 4:3, or similar in the 16:9 format. Most corporate shows are using the 16:9 format, so you might get a better deal on the 4:3 sizes, and I doubt you'll be projecting in HD format anyway. Maybe consider two or three projectors and an 8x24' or 10x30' screen, which used to be standard for multi-image slide shows. The fast fold screens can be ordered with legs as totally self-supporting, or flown; and with a "trim kit," which adds black velour valence, skirt, and legs.

    It's tricky keeping the screen as far US as possible, and keeping all stage lights, especially spill from PARs and Fresnels off of it, but it's critical.
     
    Last edited: Sep 24, 2008
  3. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    Yes...so I might be able to offer some tips.. Your drop in the back--best if it is a REAL "rear screen" as that is often very helpful for light transmission of the projector AND for clarity sake of the images shown.. Using spandex or a regular cyc or plastic screen won't really cut it and you will lose intensity.. Anyone who has tried to use a front screen in rear knows how awful the image quality can be and how half the intensity can get lost. So if possible--a real rear screen is best Also--FRONT projection may be a better option for you simply for image size control unless you have 15-20 feet behind the drop to mount a projector.. If you only have a few feet--your image size will be dependant on the lenses that are available for the projector you rent...and that is often not as easy..

    What you can do--ideally get the brightest projector you can afford to rent..something in the 5k lumens area or better is often bright enough for most general stage lighting to be seen.. The generic Office-type projectors are usually too dim or in the 1500-2k lumen range but they work great for boardrooms. Failing a really super bright projector--and if you have the time and patience, you can try to run two smaller lumen projectors that image overlap and stack them on top of each other(they make projector mounts that do this stacking and lock into place for alignments).. Put a piece of gaff tape over the projector IR window when you adjust each of the projectors if they are identical and use the same remote. You then need to run a signal splitter or see if the projectors have the ablity to parallel the input signal...

    Coming out of a laptop--VGA is OK but SVideo would be best for quality overall...match your inputs of the projector to what the laptop can put out. Depending on distance you are running from laptop to projector depends on whether you need an RGB amp or a other signal booster/converter or a video or Crestron-type box of some sort to help....

    IDEALLY and the last thought--you would want to put a video switcher or even a video mixer between the laptop and the projectors--to help process and adjust the images--but moreso to allow you to do a BLACK out or other fade when there are no images or you have to reboot or switch to another scene etc...otherwise everything done or that occurs on the laptop screen could go straight to the projectors..

    If you do Audio out of the laptop--you will need a PC Direct box...

    Hope that help get you started... feel free to ask questions..and I'm sure others will be able to offer alternate suggestions to mine.

    -w
     
  4. jonliles

    jonliles Active Member Fight Leukemia

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    Guys-
    thanks for the feedback. Fortunately my playspace is well DS of where the scrim will be (yes unfortunartely I am limited to a white muslin scrim). My nearest light will be focus a good 10ft DS of there. I am limited to school equipment BUT they have some projectors stronger than 2K lumens. I liek the video mixer idea...any idea of cost to purchase and suppliers? I'm just a poor dad trying to help out at his daughter's school.

    Jon
     
  5. sk8rsdad

    sk8rsdad Well-Known Member Premium Member Fight Leukemia

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    Given your screen, you might be better off with front projection and shooting over the heads of the dancers to minimize unwanted shadows. You might need keystone correction to compensate for the relative positions of the projector and screen.

    We routinely used our older model EIKI projector over a 120' throw distance onto our cyclorama with reasonable success.

    If you have to project through the dancers the only real worry is the shadows they will cast onto the screen. Stage lighting will wash out any projected images on the dancers themselves.
     
  6. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    Given its a muslin cyc--I agree with sk8rsdad--front projection would be best if it is possible...and here is why: First--rear screen thru a material that is not designed to allow the most amount of light thru it will only significantly lessen the intensity of the projection image. Additionally the clarity will suffer.. If 2k projectors is all you have to work with--rear on a muslin cyc will be about half what it is on the front side. If you are battling stage light bleed--having the full intensity will help you a lot. Yes--there are projector decks which can be suspended from a fly pipe--you just need to run longer cables and get a video image amplifier...some switchers often have one built in.. or you can go farther out front if you have the lense--but the farther away the more lumens you reduce by distance..

    Where to get a Video mixer or switcher or a projector mount and longer cables--your local AV house should have them easily... Mixers are cheap and simple switchers are also inexpensive to rent. Just be prepared to discuss your project, connections (i.e. bnc, svid, vga etc) and inputs/outputs and distances etc. KRAMER is a common simple switcher brand to look at for example...around here they run about $40 a day max. Also--you can always check your local high school or university--their TV studio departments often have old gear like switchers and mixers laying around that could be borrowed...or be turned into a 'project' for the TV students to help you with...

    Not tryin to tell you that you cannot do with what you have--only how to improve what you have to work with... Hope this helps.

    -w
     
  7. museav

    museav CBMod CB Mods Departed Member

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    Lumens is a measurement of the projector output and distance has no affect on the projector output or the image brightness, the factors in what hits the screen are the projector output and the image size. So whether the projector is 10' away or 100' away makes no difference as long as the screen size remains the same.
     
  8. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    Problem with nomenclature here. You can have white muslin, or a white scrim, but not both. Muslin has a fine weave, and Scrim (sharkstooth) has too large of holes and too little of thread for a suitable rear projection surface.

    I fear you're going to have less than satisfactory results trying to rear project video onto a muslin backdrop. Consider the alternatives I listed above.
     

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