# Projector Replacement Question



## Frank (Jun 2, 2011)

Our small theater sometimes projects onto a drop-down scrim using an older InFocus X2 projector. We're looking for a backup unit that should have similar specs, if not better. The X2 has 1700 lumens and 2000:1 contrast. Researching on the internet seems to show that a lot of current offerings have better specs at a lot lower cost. I don't know much about projectors: what else is important? We're replacing the old scrim with better material but I need to find a backup before mid-July as projection will be an integral part of our next show.

Ideas, advice, comments, etc. appreciated!


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## robartsd (Jun 2, 2011)

Frank said:


> Our small theater sometimes projects onto a drop-down scrim using an older InFocus X2 projector. We're looking for a backup unit that should have similar specs, if not better. The X2 has 1700 lumens and 2000:1 contrast. Researching on the internet seems to show that a lot of current offerings have better specs at a lot lower cost. I don't know much about projectors: what else is important? We're replacing the old scrim with better material but I need to find a backup before mid-July as projection will be an integral part of our next show.
> 
> Ideas, advice, comments, etc. appreciated!


 
There are lots of factors that go into a projector system. Things to think about when selecting a projector: What kind of video do you project? Does the projection need to be strong enough to use with lights up? What is your throw distance? How big does the projection need to be? How far away from the audience is the projection? How much noise can the projector make without causing an issue? What signals must the projector accept?

There are many online forums for home theater systems where projectors are discussed in abundance.

Many projectors use DLP—an array of tiny mirrors reflect the light through a filter to create the image. In high end projectors, three DLP arrays allow for all colors to be imaged simultaneously; however, low end DLP projectors utilize a single array and a spining color wheel. Some people experience a "rainbow effect" if the color wheel system is not fast enough. All DLP projectors have excellent contrast ratios. To get high brightness ratings, they often have a clear segment on the color wheel—brightness not available to saturated colors. So both the brightness and contrast numbers can be more about marketing that about actual results for a given purpose.

You'll also find LCD based projectors. Since the LCD is used to block the light, these projectors have more difficulty achieving the highest contrast ratios—do pay attention to the contrast ratio when selecting and LCD projector. They also tend to exhibit a "screen door" effect—a grid of thin black lines between the projected pixels.

So at the low end you trade off between the "rainbow effect" on DLP and the lower contrast and "screen door" on LCD; but higher quality projectors are able to mitigate these issues with either technology.

One more thing about brightness ratings—many projectors have a high output mode and an economy mode. Of course the high output mode consumes bulbs much faster. It also tends to run the fans much louder.


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## museav (Jun 2, 2011)

robartsd said:


> There are many online forums for home theater systems where projectors are discussed in abundance.


And while there can be a lot of good information on those forum, it is also often relates specifically to home theater applications and is not always applicable to many professional/commercial projection applications.

Contrast ratio is a good example as it is the image contrast ratio, which is the ratio of the light level off the screen between full white projected to the 'black' with the existing ambient lighting, that really matters and the contrast ratio of just about any modern projector is not usually much of a concern in that regard unless you have virtually absolute blackout ambient light conditions. The Digital Cinema Initiative specifications for cinemas call for a relatively low reflected white level of 14ftL and a very low reflected ambient light level of 0.01 ftL, thus an image contrast ratio of 1,400:1, a figure met by many modern projectors (apparently including their existing projector). However, while that low of an ambient light level may be feasible in home theaters it is very difficult to achieve in other venues, including theatres, without pretty extreme light control. As an example of just how much that can be relevant, the InfoComm image contrast ratio standard currently undergoing public review for other AV applications identifies image contrast ratios between 15:1 for non-critical applications to a maximum of 80:1 for critical applications. Those contrast ratios are well below just about anything you'll find for a projector.

I do agree that many of the numbers for projector brightness and contrast ratio are often pretty idealistic and are routinely based on ideal conditions that may not be valid in most real world applications. Put simply , assume that the lumen and contrast ration values for a projector are maximum values and that the actual values in use may be lower, especially after some hours of use as lamp output usually decreases over time.

Typically the most critical factors that you did not list would indeed be the image size and throw distance, the distance from the projector to the screen (or scrim in this case). Also potentially relevant would be the relationship of the projector to the screen vertically and horizontally.


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## Frank (Jun 2, 2011)

Thanks for the discussion. We currently mount the X2 off a light bar that turns to be just about the middle of the screen area. It has keystone adjustment that keeps the image pretty decent. It's ~10m from the scrim with an acceptable image size (I think it's about 20-21 feet diagonally, pretty large actually.)

We notice the "screen door" effect when shining the blue setup light onto a screen. It's more noticeable up close of course.

Another question please: the specifications give 800 x 600 (native) / 1024 x 768 (resized) as resolutions. Does this mean that it's possible to resize the input to obtain higher resolution at the "cost" of a smaller image?

thanks again


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## ruinexplorer (Jun 3, 2011)

The native resolution is what the projector will project. The 1024x768 resolution is "scaled" to fit the lower resolution. So, you will lose clarity if you send the higher resolution to that projector, possibly making some text illegible. Ideally, you want to send the same resolution as the native resolution for the best image quality. 

Another way to improve your image is what you are displaying on. If you are truly projecting on a scrim, then you are projecting on a material that allows the light to pass through and limits the amount reflected. Now, even if you meant cyc (the backdrop that many facilities end up using), then you will have a higher amount of light reflected towards the audience and potentially a sharper image due to a more even surface, but still falls short of a screen material. There are several types of materials that are suited for projection and may be something that you want to consider as part of your upgrade budget.


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## BillESC (Jun 3, 2011)

You didn't mention a budget but I'll make a suggestion anyway.

BenQ MX812ST is a short throw projector featuring 3500 lm and a 4600:1 contrast ratio. This short throw projector will give you a 20' diagonal image from just 9.72' and offers keystoning up to 40%. MAP price is $ 1799.00


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## museav (Jun 4, 2011)

BillESC said:


> You didn't mention a budget but I'll make a suggestion anyway.
> 
> BenQ MX812ST is a short throw projector featuring 3500 lm and a 4600:1 contrast ratio. This short throw projector will give you a 20' diagonal image from just 9.72' and offers keystoning up to 40%. MAP price is $ 1799.00


I had the impression the purpose was for the projector to be a backup for the existing projector (or vice versa) so that would seem to mean it needing to support the same 10m (33') throw distance.

I might also consider looking at a projector that can handle any required offset, or as much of it as possible, via lens shift rather then keystone correction. And if the projector is awkward to access I might also look at power zoom and focus. However, these capabilities can also add to the cost so it is a case of assessing both the related cost and the potential benefit.

FWIW, according to BenQ's web site the maximum keystone adjustment on the BenQ MX812ST is +/-30% and is limited to only vertical keystone correction.


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## Frank (Jun 4, 2011)

The existing material is an old scrim that's been doubled over and one of our thoughts is that by replacing it with scrim material that we might be able to use it sometime via backlighting, etc. as part of a show. I know that Rosco has screen materials that would offer a better projection surface. Is there some sort of cyc material that would be a compromise between actual screen surface and a scrim?

I'm seeing a lot of nice projectors out there but they're way beyond our current budget. One reason I'm thinking backup is that projection is an integral part of our next show and if the X2 fails for some reason we're in deep doo-doo.


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