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Keystone

 
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AFryia



Joined: 09 Mar 2006
Posts: 743
Location: S.E. Michigan


PostLink    Posted: Sun Nov 18, 2012 12:58 am    Post subject: Keystone Reply with quote


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I'm curious.

Does the JVC D-ILA projector have any optical keystone or lens shift or is keystone all digital?

Is a typical JVC setup for a certain projection angle 10-15 deg. maybe? Or are you forced to use digital keystone?
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CIR Engineering



Joined: 25 Aug 2008
Posts: 2479
Location: Chicago USA & Berlin Germany


PostLink    Posted: Sun Nov 18, 2012 3:34 am    Post subject: Reply with quote

There is no optical keystone on a JVC.

Digital keystone ruins 1:1 mapping and really screws up the image quality. It should be totally avoided. The only reason it's their is so that incompetent installers can mask their incompetence.

craigr

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Last edited by CIR Engineering on Sun Nov 18, 2012 5:13 am; edited 1 time in total
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AnalogRocks
Moderator


Joined: 08 Mar 2006
Posts: 21084
Location: Toronto, Ontario, Canada

TV/Projector: Sony 1252Q, AMPRO 4000G


PostLink    Posted: Sun Nov 18, 2012 5:07 am    Post subject: Reply with quote

CIR Engineering wrote:
There is no optical keystone on a JVC.

Digital keystone ruins 1:1 mapping and really screws up the image quality. It should be totally avoided. The only reason it's there is so that incompetent installers can mask their incompetence.

craigr


That's a great quote Craig!

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AFryia



Joined: 09 Mar 2006
Posts: 743
Location: S.E. Michigan


PostLink    Posted: Wed Nov 21, 2012 9:29 pm    Post subject: Reply with quote

CIR Engineering wrote:
There is no optical keystone on a JVC.

Digital keystone ruins 1:1 mapping and really screws up the image quality. It should be totally avoided.

Craig how is geometry maintained when mounted to the ceiling with say a 15 degree down angle?
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WanMan



Joined: 19 Mar 2006
Posts: 9668



PostLink    Posted: Thu Nov 22, 2012 11:13 am    Post subject: Reply with quote

Screen tilt?
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CIR Engineering



Joined: 25 Aug 2008
Posts: 2479
Location: Chicago USA & Berlin Germany


PostLink    Posted: Thu Nov 22, 2012 6:20 pm    Post subject: Reply with quote

AFryia wrote:
CIR Engineering wrote:
There is no optical keystone on a JVC.

Digital keystone ruins 1:1 mapping and really screws up the image quality. It should be totally avoided.

Craig how is geometry maintained when mounted to the ceiling with say a 15 degree down angle?

Usually you can use lens shift to move the image down without keystone.

craigr

_________________
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Photo Research PR-650 Spectroradiometer
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Phone: 865-405-6892
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ecrabb



Joined: 13 Mar 2006
Posts: 12668
Location: Iowa

TV/Projector: JVC RS45


PostLink    Posted: Thu Nov 22, 2012 7:01 pm    Post subject: Reply with quote

Guys... "Optical keystone correction" IS lens shift! So, the JVC most definitely has "optical keystone correction"!

The JVC is one of the more flexible (for the price) projectors with a long zoom range of 1.4-2.8:1, plus both horizontal and vertical lens shift. All are motorized, and there's a memory save/recall so you can save presets for different size/shift of the projected image, i.e. scope and pillar-boxed 1:78 on a scope screen.

The zoom has an atypically big range of 1.4-2.8:1. The vertical lens shift range is also big - about 80% of the screen height plus or minus, and the horizontal range is 34%. Using one does reduce the range of the other, so ideally mount the projector on the screen centerline.

As Craig mentioned, there is no good reason to mount the JVC's at anything other than perpendicular to the screen, and you certainly would want to avoid any digital keystone at all costs.

There's a JVC hanging in my theater these days, so if you have questions, ask away. Wink

SC
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ecrabb



Joined: 13 Mar 2006
Posts: 12668
Location: Iowa

TV/Projector: JVC RS45


PostLink    Posted: Thu Nov 22, 2012 7:06 pm    Post subject: Reply with quote

Here's a section from the JVC manual on lens shift... You can see how big the shift range is.

Happy Thanksgiving!

SC



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AFryia



Joined: 09 Mar 2006
Posts: 743
Location: S.E. Michigan


PostLink    Posted: Fri Nov 23, 2012 4:16 pm    Post subject: Reply with quote

ecrabb wrote:
Here's a section from the JVC manual on lens shift... You can see how big the shift range is.

Happy Thanksgiving!

SC,

Is your PJ ceiling mount? Are you using screen tilt?

When the time comes I'll be mounting on the ceiling. With that in mind based on your experience what do you feel is the best setup?

1 - 100% lens shift
2 - 100% screen tilt
3 - or some combination of both
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ecrabb



Joined: 13 Mar 2006
Posts: 12668
Location: Iowa

TV/Projector: JVC RS45


PostLink    Posted: Fri Nov 23, 2012 6:20 pm    Post subject: Reply with quote

Yes, mine is ceiling mounted. No tilt - my screen is exactly as it was with my g70: perfectly plumb.

Unless you specifically wanted to introduce some tilt, you wouldn't have to.

Personally, I can't really see any good reason for it, unless for instance your screen was well above the normal height relative to the viewers.

SC
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