Want to add a lens to fill entire screen space - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 14 Old 02-15-2020, 12:36 AM - Thread Starter
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Want to add a lens to fill entire screen space

I want to add a lens at the front of my projector for a larger image. I saw a video online for a DIY method. However I want to create the rig myself. I just need to know what lens would I need to get? I have a non short throw projector and the zoom is at the maximum setting for the room size and I cannot put the projector further back. Therefore I want to use a lens add on. Cannot afford the Navitar option so I want to try a DIY method to put a lens in front of the current projector lens. I just don't know what lens should I get.

Further information:

Projector: Optoma HD200X-LV
Screen = 16:9

See the below image. The grey area is the screen and the blue area is the maximum projected image that can be gained from the projector.

I want to add a lens in front of the projector that can allow me to fill the entire screen space.

What lens shall I try? Shall I get a 50mm lens for about $25 online? Can you recommmend some?

Here is the current lens information for the lens that is in the projector:

F= 2.55-2.87, f= 22.4–26.8mm,
1.2x Manual Zoom

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post #2 of 14 Old 02-15-2020, 12:38 AM - Thread Starter
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Quote:
Originally Posted by tarults View Post
I want to add a lens at the front of my projector for a larger image. I saw a video online for a DIY method. However I want to create the rig myself. I just need to know what lens would I need to get? I have a non short throw projector and the zoom is at the maximum setting for the room size and I cannot put the projector further back. Therefore I want to use a lens add on. Cannot afford the Navitar option so I want to try a DIY method to put a lens in front of the current projector lens. I just don't know what lens should I get.

Further information:

Projector: Optoma HD200X-LV
Screen = 16:9

See the below image. The grey area is the screen and the blue area is the maximum projected image that can be gained from the projector.

I want to add a lens in front of the projector that can allow me to fill the entire screen space.

What lens shall I try? Shall I get a 50mm lens for about $25 online? Can you recommmend some?

Here is the current lens information for the lens that is in the projector:

F= 2.55-2.87, f= 22.4–26.8mm,
1.2x Manual Zoom

Screen image here:

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post #3 of 14 Old 02-15-2020, 12:41 AM - Thread Starter
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Sorry, I cannot add images or links until I have 5 posts. But essentially I have a screen and even when I project the maximum zoom onto the screen, there is still about 6 inches of blank screen space around the entire projected image. I therefore want to fill that space by adding a lens in front of the existing lens that can enable a great zoom.
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post #4 of 14 Old 02-15-2020, 01:20 AM
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One solution to your common problem is to use a mirror to increase your throw distance. Two ways to do this is to mount the projector backwards and bounce the image off a mirror back to the screen. The other is to mount the projector sideways and place a mirror at a 45 degree angle bouncing image back to the screen. I have not seen much success using a lens. Mirrors are cheap to experiment with but you get a little better result with a front/first surface mirror often found in old fiche viewers/RPTV's.

EDIT: Of course if you had done your homework and bought a shorter throw projector like the BenQ lineup you would't have this issue.

"Smart enough to know better, to old to care" ------ Dedicated Bat Cave Home Theater, JVC RS49U/Mitsubishi HC7900DW Projector, 110" 16:9 Jamestown screen with variable power masking for CIW 2.50:1 to 16:9, Marantz 7009 with 7.1.4 Atmos with Ohm mains,3 DIY Subs (2 15" (1 ported, 1 sealed and a 12" 4th order bandpass), 1 DIY butt kicker, Custom Built HTPC, 18TB DroboFS NAS

Last edited by rekbones; 02-15-2020 at 01:25 AM.
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post #5 of 14 Old 02-15-2020, 03:31 AM
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Yes, the mirror method is the better method, considering that getting the DIY lens to work without distortion is highly unlikely.

If you only have a few inches left to fill on your screen, then a relatively small mirror will do. This is rather easy to verify by making a drawing. You simply turnt the projector backwards and a vertical mirror will extend the light beam in the opposite direction without changing its angle. If you do need to change the angle, you can then tilt the mirror to compensate for that.


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post #6 of 14 Old 02-15-2020, 09:06 AM
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post #7 of 14 Old 02-15-2020, 11:41 AM
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Can you provide screen size and distance from the projector lens to the screen?
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post #8 of 14 Old Yesterday, 10:12 PM - Thread Starter
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Quote:
Originally Posted by rekbones View Post
One solution to your common problem is to use a mirror to increase your throw distance. Two ways to do this is to mount the projector backwards and bounce the image off a mirror back to the screen. The other is to mount the projector sideways and place a mirror at a 45 degree angle bouncing image back to the screen. I have not seen much success using a lens. Mirrors are cheap to experiment with but you get a little better result with a front/first surface mirror often found in old fiche viewers/RPTV's.

EDIT: Of course if you had done your homework and bought a shorter throw projector like the BenQ lineup you would't have this issue.
Thanks! What is the difference in image quality when using a mirror compared to without the mirror? If the image without the mirror is rated at a 10, how close in terms of quality is the image with the mirror - an 8 or 9?

Yes, I should have done more homework!
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post #9 of 14 Old Yesterday, 10:15 PM - Thread Starter
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Quote:
Originally Posted by descalabro View Post
Yes, the mirror method is the better method, considering that getting the DIY lens to work without distortion is highly unlikely.

If you only have a few inches left to fill on your screen, then a relatively small mirror will do. This is rather easy to verify by making a drawing. You simply turnt the projector backwards and a vertical mirror will extend the light beam in the opposite direction without changing its angle. If you do need to change the angle, you can then tilt the mirror to compensate for that.


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Thanks! Where can I buy cheap mirrors? Any clue on robust mounting options on the wall at the back of the room without drilling or sticking? Maybe a clip on option that can clip to a shelf?
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post #10 of 14 Old Yesterday, 10:18 PM - Thread Starter
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Originally Posted by bud16415 View Post
Excellent work with your room, bud! Can you provide some guidance for a DIY screen project? I can provide concept design for what I want to achieve.
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post #11 of 14 Old Yesterday, 10:26 PM - Thread Starter
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Quote:
Originally Posted by bdht View Post
Can you provide screen size and distance from the projector lens to the screen?
Screen size based on 16:9:

Height: 64.13"
Width: 114"
Diagonal: 130.8"

Lens to screen distance is: 173.5" (or 14' and 5.5")
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post #12 of 14 Old Yesterday, 10:29 PM
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Quote:
Originally Posted by tarults View Post
Screen size based on 16:9:

Height: 64.13"
Width: 114"
Diagonal: 130.8"

Lens to screen distance is: 173.5" (or 14' and 5.5")
The projector says 1.5 to 1.8 throw, that should fit... youre at max zoom and its not filling the screen?
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post #13 of 14 Old Yesterday, 11:01 PM - Thread Starter
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Quote:
Originally Posted by bdht View Post
The projector says 1.5 to 1.8 throw, that should fit... youre at max zoom and its not filling the screen?
The projecter is currently shelf mounted at the top of a book case at the back of the room. Well it is on the very last shelf on the book case and I can go further by placing it at the top of the bookcase. Ceiling mounting is not an option. The back legs have books under them (so they can be raised) and the projector is therefore tilted. I am therefore keystoning via the keystone settings. Not a lot of keystone options on this model but I have it available.

Come to think about it, I think I am losing width because my projector is tilted as per the below diagram. Therefore if I can find a way to reduce the tilt and raise the projector, maybe my screen may be filled?

https://www.creativeapplications.net...etDiagrams.png

And yes, I am at max zoom and not filling the screen.
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post #14 of 14 Old Yesterday, 11:28 PM
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Quote:
Originally Posted by tarults View Post
The projecter is currently shelf mounted at the top of a book case at the back of the room. Well it is on the very last shelf on the book case and I can go further by placing it at the top of the bookcase. Ceiling mounting is not an option. The back legs have books under them (so they can be raised) and the projector is therefore tilted. I am therefore keystoning via the keystone settings. Not a lot of keystone options on this model but I have it available.

Come to think about it, I think I am losing width because my projector is tilted as per the below diagram. Therefore if I can find a way to reduce the tilt and raise the projector, maybe my screen may be filled?

https://www.creativeapplications.net...etDiagrams.png

And yes, I am at max zoom and not filling the screen.
Yes keystone is effecting your throw distance. Turn the projector upside down and get it as close to the top of the screen as you can to avoid keystone. That model is not designed to be shelf mounted. Get some foam to cradle the projector in so it can be inverted.

EDIT: You should be able to shoot a 132" diag 16:9 image with a throw of 14' 5" with digital keystone at zero. The projector needs to be a few inches above the top of the screen inverted/level to get digital keystone to zero.

"Smart enough to know better, to old to care" ------ Dedicated Bat Cave Home Theater, JVC RS49U/Mitsubishi HC7900DW Projector, 110" 16:9 Jamestown screen with variable power masking for CIW 2.50:1 to 16:9, Marantz 7009 with 7.1.4 Atmos with Ohm mains,3 DIY Subs (2 15" (1 ported, 1 sealed and a 12" 4th order bandpass), 1 DIY butt kicker, Custom Built HTPC, 18TB DroboFS NAS

Last edited by rekbones; Yesterday at 11:36 PM.
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