Throw distance for JVC X3 w/FVX200 lens? - AVS Forum
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post #1 of 14 Old 04-28-2011, 08:27 PM - Thread Starter
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Does anyone know of a throw distance calculator for this combination. The calculator on the JVC site has a Panamorph option, but not sure if it is specific to this lens. I need to calculate the minimum distance to fill a 122.5" diagonal 2.35:1 screen. The JVC calculator comes up with 15'. Does that sound correct?

Thanks in advance for any insight.

Mark
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post #2 of 14 Old 04-28-2011, 11:39 PM
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Is this their small VC lens with glass optics? If so you need to multiply the scope screen width by at least 2.

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post #3 of 14 Old 05-04-2011, 06:19 PM
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When you set up an anamorphic lens projector combination, the projector is set up for the 16 x 9 screen that fits within the higher aspect ratio screen. The size of that 16 x 9 screen is the height of the wide screen and the width is 1.78 times that height. That width is the width you multiply by the throw ratio you wish to use and the multiplication product is the throw distance. generally when you have a throw range, here for your projector of approximately 1.4 through 2.8, you want to mount very close to the maximum number. Thise minimizes pin cushioning and keeps the chip imasge exiting the projector lens as small as possible enabling you to keep the image within the sweet spot of the anamorphic lens. Also mounting the anamorphic as close as possible to the front of the projector lens also keeps the chip image entering the anamorphic as small as possible. The smaller the diameter of the anamorphic, the more imporetant all this is. The larger the diameter of the anamorphic, the larger the sweet spot and the larger the entering image can be without optical degradation.

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post #4 of 14 Old 05-04-2011, 07:46 PM - Thread Starter
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My installer determined that the 200 series lens was not going to work so he replaced it with the UH480. Now, we are covering the screen ok but have a fair amount of bowing (which I guess is what people refer to as pin cushion). I'd appreciate any insight into what I should expect and what would be considered normal pin cushion for my setup. My installer doesn't seem to have much experience with this lens and I'm starting to worry that his design is just not going to work.

Anyway, here is my setup:

Projector: JVC X3
Lens: Panamorph UH480
Screen: Stewart 2.35:1 48" tall, 85.25" wide (masked) 112.75" wide (unmasked), 122.5" diagonal
Throw distance: 13' 3"
Center of projector lens is about 2" above the top of the screen
Projector mounted level
Lens tilted down (quite a bit, not sure how to measure this)

Here is what I'm seeing: Lines on the bottom of the screen look pretty straight. At the top, I'm seeing a bow with the edges being higher than the center by about 1 1/2". That seems like quite a lot to me, but I'm new to this so not really sure. Is that the best than can be expected, or should I keep making adjustments?

Thanks in advance.
Mark
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post #5 of 14 Old 05-04-2011, 08:11 PM
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Your throw ratio is about 1.87. This is far from ideal. The pincushioniong you have is about what would be expected at this throw using that lens. Just zoom the picture out to keet the pincushioning off screen. You could make things better by going to a longer throw and by using a curve screen.

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post #6 of 14 Old 05-04-2011, 08:18 PM
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You adjust the lens swivel up and down until there is an equal amount of pincushion at the top and bottom. In your case there should be about 3/4" at top and bottom.
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post #7 of 14 Old 05-04-2011, 09:05 PM
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Quote:
Originally Posted by CAVX View Post

Is this their small VC lens with glass optics? If so you need to multiply the scope screen width by at least 2.

Quote:
Originally Posted by mark haflich View Post

When you set up an anamorphic lens projector combination, the projector is set up for the 16 x 9 screen that fits within the higher aspect ratio screen. The size of that 16 x 9 screen is the height of the wide screen and the width is 1.78 times that height. That width is the width you multiply by the throw ratio you wish to use and the multiplication product is the throw distance

For a Horizontal Expansion lens, yes. When I assisted above, he was considering a Vertical Compression lens which is calculated off the Scope screen with and won't pincushion, it barrels.

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post #8 of 14 Old 05-04-2011, 09:08 PM
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Quote:
Originally Posted by knmlee View Post


Projector: JVC X3
Lens: Panamorph UH480

Throw distance: 13' 3"

Are you able to move that back to at least 14.5 feet? You have to be in the "sweet spot" (14.5~17) for the UH480's corrector to work for you.

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post #9 of 14 Old 05-04-2011, 09:36 PM - Thread Starter
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Quote:
Originally Posted by CAVX View Post

Are you able to move that back to at least 14.5 feet? You have to be in the "sweet spot" (14.5~17) for the UH480's corrector to work for you.

Not without rerouting some heating ductwork

Is there a different lens that would work better than the UH480 at this distance?

After looking at some actual program material this evening (instead of test patterns), I was quite impressed. Maybe once I get it adjusted evenly on top & bottom it will be less noticeable??
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post #10 of 14 Old 05-04-2011, 09:59 PM
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Hi Mark (Techer). Sorry I missed that the first lens wasn't horizontal expansion. Are you coming to Cedia this year?

Mark (thread starter). Sorry I missed that the pincushioning was only at the top. As the experts have stated, adjust the tilt on the anamorphic to equalize the pin cushioning so its split between the top and bottom. 3/4 inch top and bottopm is about where it should be given the set up. You can't easily move the throw back so, the solution is to just zoom the picture to get the 3/4 off screen. Its a small amount of zoom and a small loss in total picture area lost.
With the panamorph and most horizontal anamorphics, you need to be at a throw of about 2.0 or greater. The throws Mark T is recommending are 2.0 to about 2.4. Life isn't perfect and most HTs invove tradeoffs and compromises. A curved screen should just about eliminate all pin cushioning in your set up and that while not really cheap it is at least physically doable without duct relocation.

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post #11 of 14 Old 05-04-2011, 10:08 PM
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Quote:
Originally Posted by mark haflich View Post

Hi Mark (Techer).Are you coming to Cedia this year?

Hi Mark, no CEDIA this year as this years 'play money' is being spent on Sammy and I getting married

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post #12 of 14 Old 05-05-2011, 01:05 PM
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I assume its the young lady I met at Cedia? You lucky dog. Congratulations.

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post #13 of 14 Old 05-05-2011, 03:58 PM
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I assume its the young lady I met at Cedia? You lucky dog. Congratulations.
The very one

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post #14 of 14 Old 05-06-2011, 10:19 AM - Thread Starter
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Quote:
Originally Posted by coolrda View Post

You adjust the lens swivel up and down until there is an equal amount of pincushion at the top and bottom. In your case there should be about 3/4" at top and bottom.

Thanks for the tip. That works quite well for the scope material. I've zoomed out so the worst distortion is off the screen. Watched "The Fighter" last night and never noticed any distortion.

I can't say the same for 16:9 material. Mostly, I watch movies (which seem fine) and sports on DirecTV. The sports channels are quite disappointing. I definitely can see the loss in horizontal resolution and the curved lines and screen tickers are quite annoying. There is no way I will be able to stand this over the long term.

I think that I'm going to add a sled to my setup and move the lens out of the way for 16:9. The bracket that came with the lens supports both a manual and motorized sled. That should give me a reasonable setup with scope material through the lens and 16:9 without any distortion.

My only other option would be to scrap the JVC and lens and get a Panasonic projector setup for zoom. Obviously a lot cheaper, but also smaller an less obtrusive in my room. The JVC with lens is huge.

A curved screen is not an option (unless I can get my installer to pay for it)... As it is, the screen I have is the most expensive part of the setup. It is a Stewart with motorized masking and microperf material. The speakers (Triad silvers) are installed behind the screen in wall. They sound terrific.

Any thoughts on the lens vs zoom option (given my 1.86 TR)?

Thanks,
Mark
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