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Discussion Starter · #1 ·
http://www.hometheatershack.com/for...e4000u-there-such-thing-much-little-zoom.html

http://www.hometheatershack.com/for...ight-least-trying-new-movie-room-build-2.html

This is the second thread I've read about this restriction that the projector has to be mounted no higher than the top of the screen when using the auto zoom feature. I just don't understand the restriction in this case....it makes no sense that you wouldn't be able to use the lens shift functionality to allow the projector to be mounted higher than the top of the screen. Even if the projected image shifts up or down on your screen during the zoom, you still have the ability to move the digital image up and down in the projected image using the V-Position adjustetment. Maybe the autozoom already does this and maxes out the capability...I don't know. Can someone using this projecter and the autozoom function on a CIH screen help me out here.
 

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Discussion Starter · #2 · (Edited)
Ok...after some research, I think I got a handle on this. I had to draw it up in CAD before I really fully understood. The problem is the way in which the projector uses lens shift, but it makes sense why. Lens shift is defined as the distance from the center of the projected image to the center of the lens. In this case, it is much easier to think of it as a percentage of projected 16:9 image height.

If you have a 48" projected 16:9 image, and you are using 100% lens shift, then your projecter is 48" above the center of your screen.

The crux of the situation here is that when you zoom, the lens shift percentage remains the same. That means that when you zoom your picture to display only the 2.35 portion of the image on your CIH screen, the 16:9 projected image and the dimension of offset created by lens shift grow at the same ratio.

In this same senario, when you zoom to fit the 2.35 portion of the image onto your 48" tall screen, the actual projected height of the 16:9 image grows to 64". If you were using 100% lens shift, then the center of your 16:9 image would be 64" below the projector. The projector does have the cabability to digitally shift the image up or down within the confines of the projected image....but is that enough...the answer is no.

Below are CAD layouts showing this senario for different percentages of lens shift from 100% down to 50% (the point at which the projector is below the top edge of the screen) The red image cone is for a 16:9 image zoomed out. The green cone is for a 16:9 image zoomed in 33%, which would be used to reframe the 2.35 portion onto your CIH screen.

You will see that the corresponding growth in image offset due zoom pushes the projected image down below the top of the screen for lens shift values greater than 50%

100%


90%


80%


70%


60%


50%
 

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Discussion Starter · #3 · (Edited)
This means only one thing for me.....Panasonic has issued me the challenge to automate my lens shift :nerd: Can anybody who has this projector tell me how many turns it takes to turn the lens shift dial from one extreme all the way to the other?
 

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Elite Shackster , HTS Moderator Emeritus
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Sorry I can't help with this, but I am interested in your results. I've installed a couple of these in the last year or so, but I haven't measured stop-to-stop on the shift. I also haven't used the auto-zoom feature either. I've found it very easy to dial in with just the shift and manual (sort of) controls.

Good luck.
 

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The Panasonic PJ are very Install friendly and has more lens shift than other PJ that I have used, I have a 92" screen and the PT-AE3000 only took approx 5 minutes of setting up, the 4000 is more of the same.

My PJ is approx 13ft from my screen and gives a stunning picture, I have only done basic calibration...meaning brightness and contrast/black and white calibration.
 

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Discussion Starter · #6 ·
what was I thinking...automate the lens shift...... keep it simple stupid. Ever heard of a motorized projector mount. Depending on your screen size, you would only need to lift the projector by 4 to 8 inches to compensate for the screen offset in the zoomed mode. Looks like it's time to break out the erector set.
 

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Elite Shackster , HTS Moderator Emeritus
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Look into the robotics sites. They have actuators that are very stable, pretty cheap, and can be controlled within fairly tight tolerances (0.1" for a cheap one, 0.01" for a better one). I don't know what your budget is, but I've seen these for $20 to $40. Controlling it would be another story.

Another option is a rack and pinion with a servo motor. You can either have hard stops or use a controller as well. you would have to build some sort of track or scissor.

Good luck and post pics!
 

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Discussion Starter · #8 ·
Yeah...haven't quite thought out the exact mechanism yet, but I was thinking simple relay control and position switches. It's not high tech, but very reliable. The projector has the ability to output a 12V trigger for when it changes modes, so it would be a piece of cake to fully automate the control circuit. I will also use that to trigger a masking mechanism too.
 

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Here are some pictures of a projector lift: http://www.avsforum.com/avs-vb/showthread.php?t=1259917. Go to the middle of the page, or search for "projector lift". Pretty cool if you can set it up against a wall.

Several Epson 2011 models include automated lens shift. The Espon Home Cinema 21000 is to be sold for $3,500. It also has lens memories, obviously meant to compete with the popular Panasonic PT-AE4000. But I've seen discussions based on early demo's that the lens memories did not work well. The lens shift is also suspected to be inaccurate. But no one knows for sure. Their release is delayed, currently probably set in March. I'd wait for professional reviews.

If you don't mind stepping away from pure CIH setup (single scope screen), using dual screens (one fixed frame, one electric dropdown) has the side benefit of overcoming the mounting limitation. You simply position the 16:9 screen TALLER than scope screen. Problem solved. In my case, my projector is at least 18" above the top of scope screen. BTW, you also get full masking in all AR's, and have the option to have balanced image sizes (as opposed to smaller 16:9 image in a CIH setup) and form a Constant Image Area (CIA) setup. Just another option. Check out the pictures in my signature.
 
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