# Question about Lumens output versus Zoom Lens position



## giboni (Apr 27, 2011)

Hi everyone,
This is a great forum. Have learned so much in just a few days. Did try by searching to answer my own question.
Projector is BenQ SP890. It is literaly in the mail. About 5 days. The screen is coming together tomorrow.
2:35-1, 300 inch diagnol, 8feet 9inches by 276.00 inches 23 feet length. Table mounted projector. 15 foot ceiling. Screen
will hang probably 2 feet from top of ceiling. I have about 30 feet from the screen to the back of the space.
Tell me if I am wrong. After confusion and reading.Think I will get the maximum Lumen output of the projector at the widest setting of the Zoom Lens? Is this assumption correct? Figure after color etc. adjustments going to loose a lot of Lumens in that process. Ah obviously the Table height is adjustable even if I need a step ladder.:rofl: Thanks in advance. :blink: Oh well. Just because it says 4000 does not mean thats what it does. Maybe I get a good refurb LOL !onder:


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## Prof. (Oct 20, 2006)

No zoom = maximum lumen output = longest mounting distance from screen..


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## RBTO (Jan 27, 2010)

Prof. said:


> No zoom = maximum lumen output = longest mounting distance from screen..


I'm a little confused by that statement. With "no zoom" do you mean the shortest focal length (widest angle) and if so wouldn't that be the _shortest_ mounting distance from the screen? I assume you meant_ maximum zoom_ (longest focal length) which allows the greatest distance (all these assuming the same size image). Please clarify.


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## Prof. (Oct 20, 2006)

Sorry for the confusion..

If you place your projector in a fixed position close to the screen, the smallest image you can obtain is when no zoom is applied..The image has to be zoomed out to obtain a larger image..

With no zoom applied, you would need to move the projector further back to get a larger image..

I hope that explains it more clearly..


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## giboni (Apr 27, 2011)

Hi thank you everyone for taking the time to answer. Okay my unit is Manual Zoom, 1.20:1. I adjust it to no Zoom.
Then place it till it fills up the screen. This way the telephoto is not used which would cut down on Lumens.
Will be using an anamorph lens also. The closer the projector is to the screen the brighter the screen gets. Other
problems might crop up. Think I understand this now.


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## Prof. (Oct 20, 2006)

When using an anamorphic lens you need to have the longest throw possible..to minimize the pincushion effect..
This means placing the projector as far back as possible..


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## giboni (Apr 27, 2011)

Okay. When everything is ready guess will learn the hard way ! In researching anamorphic lenses ostensibly
to find a cheap one. Read this from the manufacturers web site." The projected image can then be zoomed in or out to allow for the corners to “overscan” on to the blackout material". {Pincushion}
With a little luck after color adjustment and maintaining a dark space this projector just might do it on this size screen. Am going to replace the bulbs in the fire exits to very low wattage. Paint part of the ceiling in front of the projector
flat black. Installation is certainly a compromise of many factors. Thanks again for your input and time.


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## Prof. (Oct 20, 2006)

giboni said:


> " The projected image can then be zoomed in or out to allow for the corners to “overscan” on to the blackout material". {Pincushion}


Yes..that is correct..It's almost impossible to get your projector in the exact position where you have the right amount of overscan (with zero zoom) to have the pincushion distortion on the borders, so it's best to get the image almost to the edges of the screen with your mounting position and then apply a little zoom to give you the right amount of overscan..


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## giboni (Apr 27, 2011)

Hi,
Thanks again for your time and input. Definitely will remember that. Hopefully you are still on the forum ! Have another question.
Based upon a 16 foot ceiling the aforementioned screen dimensions. The screen sitting off the floor approx. [5] 4 feet 4 inches how tall will the table that the BenQ SP890 sits on have to be ? I am going to use an old heavy adjustable steel mount. Originally for an 18 inch Sub-woofer. It can hold a heavy speaker up to six feet off the floor. Figure might be a formula for this. :heehee:


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## Prof. (Oct 20, 2006)

giboni said:


> The screen sitting off the floor approx. 5 feet 4 inches


Why so high off the floor!? You'll get a crinked neck that high up!! 
Ideally your eye level should at about a third of the way up from the bottom of the screen..

I should add that at my suggested position, you will get more of an immersive feeling..


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## Prof. (Oct 20, 2006)

A further note...

I realize that this is a very big screen and to obtain the correct eye level position, you would require elevated seating..
To be able to do this requires the projector to be mounted overhead and in your room you would need a separate projection box/booth..


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## giboni (Apr 27, 2011)

Shoosh!
Just edited my post for grammar and run on sentences! Actually closer to four feet. I am going to use Van/automobile seats. Each row starting with the second will be raised up about 3 inches higher than the row in front. The other reason for the screen being this high is to use a separate screen panel underneath
the first for 1953 and older movies in 5:4 format ! I have 30feet+ from the front of the screen to the kitchen counter. Now that I think of it with your suggestion in mind. I could go the other way with a panel on a hinge to swing into place from the top or simply a felt drape to cover that screen piece !


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## giboni (Apr 27, 2011)

Ah Oh no. Honestly the space is close to 3,000+ or - 100 square feet. It is rectangular. Not sure I need a booth . However I might have to use a ladder ! The van seats will be left and right of the projector
stand and in front. If problems arise I can construct cheaply a small booth raised up. Unfortunately for safety reasons the last row will only go 1 foot above the concrete floor. It is not perfect. Still a lot of WOW for the buck in a converted to living work factory space !
Tomorrow going to call a distributor in L.I.C. on the cost 4x8 High Impact Polystyrene.020 0r .030. Check out the vinyl flooring at Home Depot. Have a feeling stretching a natural canvas will be the best bet. My original idea.
As it says in your posts. 
"Home Theater...the never ending story!"


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## Prof. (Oct 20, 2006)

That makes things a lot easier if you're having the seating either side of the projector..
Just a simple stand/cabinet about 5' high to put the projector on and use the lens shift to position the image..No ladder required!! 

If you can get a large one piece of white canvas, that would be ideal for the screen..otherwise you may have to have it joined for that size..

Edit..You may be able to get a piece of canvas that size from a Sail Maker..


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## giboni (Apr 27, 2011)

Prof. said:


> That makes things a lot easier if you're having the seating either side of the projector..
> Just a simple stand/cabinet about 5' high to put the projector on and use the lens shift to position the image..No ladder required!!
> 
> If you can get a large one piece of white canvas, that would be ideal for the screen..otherwise you may have to have it joined for that size..
> ...


Nope
?x24ft 10 ounce virgin untreated natural fine weave brass grommets 92.50+ shipping.lddude:
Miscellaneous Hardware from H.depot such as T.V. antennae guy wire etc. adjustable hardware wire ties,
$25.00. If I go with this or any other scheme. Cheap 2x3 frame ! Will take pictures & post them ! 

"Nothing is impossible to him who will try":neener:

Alexander the Great


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