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Topic: Confused about selection based on throw distance
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Joined: Oct 28, 2015
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Hi there! I am a little confused about the "Search by Feature" as well as the Calculator Pro pages, and want to make sure I'm interpreting this correctly.

I have a sort of specific use -- it is going to be used for a video in a museum exhibit. The space it will be going in is 12.5 feet from the wall being projected on, and we need the image size to be 68" wide. When I plug these two needs into the search by feature, the product I specified comes up. Then when I use the calculator pro and I set the picture width to 68", the throw distance says 10'2. The shaded blue area, though, spans from roughly 15' to 7'. Does this mean that i'll have to adjust the keystone in order to make the picture 68" at 12.5'?

My concern fueling this post is because I own a projector and when I adjusted the keystone, the remaining area that the projector is able to project to contains some residual light. The light is dark, but definitely visible. Not wanting this same issue here at work in the exhibit, I'm trying to avoid it as much as possible! I have attached an image to illustrate the residual light issue.

Any insight is greatly appreciated.

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residual light

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You don't adjust keystone, you adjust zoom. Zoom like on a camera. This is not done digitally, but done with the lens of the projector.

Keystone should NEVER be used on any projector. You should buy a projector and put it where it is supposed to go. If you need some flexibility in up/down placement with a projector, get one which has good lens shift.

Keystone correction is a digital only correction of geometry, not size. If you tilt your projector up/down then it turns the rectangular image into a trapezoid, and then you digitally correct for this. Still, the projection image is a trapezoid, so you see that image on a white wall. This is one of the reasons why projection walls should be dark or black, it will suck up that overspray.

If you actually level your projector, then move the physical location to where it is supposed to be, you won't have any keystoning issues, and you won't have to use keystone correction.

The Epson 5030, Panasonic AE8000 and some others have a fair bit of lens shift which allow for greater placement flexibility.
[Edited by AV_Integrated on Oct 31, 2015 at 7:34 AM]
AV Integrated - Theater, whole house audio, and technology consultation during the build and installation process in the Washington, DC metropolitan area.
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Thanks for your reply!

I am trying to do exactly what you suggest--purchase a projector that fits the space I have. I didn't do that for home, which I now understand. That said, I'm still not sure if I'm interpreting the calculator correctly.

When I use the calculator pro and I set the picture width to 68", the throw distance says 10'2. The shaded blue area, though, spans from roughly 15' to 7'. The place I'm mounting the projector is exactly center to the screen, so lens shift shouldn't be necessary. I've attached a snapshot of the calculator.

To the top and bottom of the screen I am able to put something black, but to the left and right of the screen there are marble walls, hence my concern for light bleeding over. I could make the screen smaller and make black edges on the L and R to catch any overflow, but of course that depends entirely on the zoom abilities of the projector since my placement is pretty much set in stone (or, at least would be very complicated to change at this junction, with the exhibit designers and construction and all). I have attached a picture of a little sketch of the setup as well, it's in the window well in a historic courthouse.

I know the calculator is an approximate. Is the best thing to do purchase it and test it, and return it if it doesn't work out?

Thanks so much,
Torii

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calculator and window sketch combined

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Torii - You will want to be very exact with your measurements, and you should not put up a mount until you are 100% certain that the lens of the projector you get is on center with the projector itself. Some lenses are a few inches off of center, which means you have to have the mount a few inches off of center as well.

You have the right idea with the projector zoom range.

The shaded blue area shows how close/far the projector can be for a given screen size. You can actually move that slider up and down to see it move.

Projector Central has a "SEARCH BY FEATURE" function which allows you to setup some parameters to search by.

For a 68" wide image with 12.5' from lens to screen, and a price under $3,000 with lens shift, these are the results...
http://www.projectorcentral.com/projectors.cfm?g=1&hide=0&st=1&mfg=&p=300&p=3000&w=&r=&br=&ll=<g=&t=&db=&dt=&c=&ar=Wide+%2816%3A9-10%29&dvi=&wr=&hls=1&pjl=&pjw=&pjh=&td=12.5&is=68&i=w&tr=&oop=1&sort=%24&sz=15

I'm not sure I would be looking for a 1080p projector vs. a business class 1280x800 projector (or similar) which is brighter and will deliver greater impact in such a space. Home theater projectors are great in 'dark' rooms, but in a lit space, I would be looking for the brightest projector my budget could afford me.

For example:
http://www.projectorcentral.com/Panasonic-PT-EW540U.htm
[Edited by AV_Integrated on Nov 2, 2015 at 12:26 PM]
AV Integrated - Theater, whole house audio, and technology consultation during the build and installation process in the Washington, DC metropolitan area.