Quick Question on Throw Ratio and Image Size - AVS Forum
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post #1 of 9 Old 01-25-2014, 01:41 PM - Thread Starter
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If I install a projector at the front side of it's throw ratio and obtain perfect image placement and size on my wall-mounted screen using the projector's zoom and lens shift adjustments, is it safe to assume that if I then move the projector to the back side of the throw ratio I can obtain the exact same image placement and dimensions on my screen using the same projector adjustments?

If I need to add additional information to help answer this question, let me know. Thanks in advance for taking the time to help me understand this.

Doug
Current PJ: Optoma HD72
Current Screen: Carada 92" 16x9
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post #2 of 9 Old 01-25-2014, 02:58 PM
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If I understand the question, yes. The difference will be the contrast (and I forget which way it is, which end of the throw has the best or worst contrast).
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post #3 of 9 Old 01-25-2014, 03:43 PM
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I'm not so sure, but I don't think you're using the term "throw ratio" in the right context.

Regardless, the easiest thing to do is to check the projector's manual for the throw / zoom diagram. It will show you the min/max image sizes possible given a specific throw distance. Too short a throw, and you won't be able to get the image large enough - too far back, opposite problem can occur (among other issues with both extremes).

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post #4 of 9 Old 01-25-2014, 07:23 PM - Thread Starter
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Thanks for the responses. And yes, @jautor, being a novice with all this I may have misused the terminology.

I understand that every projector has a Throw Ratio with a min and max value representing the optimal distance the lens should be from the screen to remain within the projectors capabilities. If I place the projector at the min ratio value (closest to the screen) and adjust the image to be where I want it, then I'm assuming that the controls and adjustments provided by the projector would allow me to move the projector back to the max ratio (furthest from the screen) and still maintain the image size and position I had at the min ratio position.

I am researching a projector that will allow me to use the size screen I want, but when I use one of the many calculators out there it shows the throw distance for that size screen to be about 2 feet forward of the current position of the ceiling mount I have now. However, the throw range of the projector permits me to move the projector back to the position of my current ceiling mount and still be right in the middle of the projectors total throw ratio range. I'm assuming here that the projector's controls/adjustments are such that wherever I mount the projector, as long as it is inside the throw ratio distances, I will be able to maintain a consistent image size and position on the screen. I do understand that contrast is affected by the projector's distance from the screen, but my only concern at this time is the position and size of the projected image.

I believe @ctviggen has confirmed my assumptions, so thanks for input!

Doug
Current PJ: Optoma HD72
Current Screen: Carada 92" 16x9
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post #5 of 9 Old 01-25-2014, 10:47 PM
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For your purposes, forget thinking about the ratio. Look at the projector's chart for the image size range possible given the distance of your existing mount. What is that distance, by the way? If we know that, you'll get better advice...

Rock Creek Theater -- CIH, Panamorph, Martin Logan, SVS PB2000, Carada Masquerade, Grafik Eye, Bar table, Green Glue, JVC RS50 
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post #6 of 9 Old 01-26-2014, 05:40 AM - Thread Starter
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Fair enough, @jautor... here are the specifics. Again, I appreciate your patience and help understanding this.

I have a room that is 8' tall with an Optoma HD72 mounted at a throw distance of 12'10" (154") onto a 92" 16x9 Carada screen with the bottom edge 2"8" above the floor. Works great. I am now considering a projector and screen upgrade and have been looking at the Epson PowerLite Home Cinema 5030UB and a 105" Carada screen. I want to mount the Epson at the exact same location as the currently mounted HD72 with the screen mounted with its lower edge the same 2"8" off the floor.

Using the Epson calculator it appears the throw distance will be 10"3" for the 105" screen and I'll have to use the lens shift to lower the image since I want the projector mounted about 8" below the ceiling.

All well and good, but I want to mount the projector back at a throw of 12'10" so I don't have to make a new hole in the ceiling and so the projector won't be located in front of the back row of seats.

Hence the dilemma. Will the projector's adjustments allow me to achieve the image size and position indicated with a throw of 10'3" if I move it back to a throw of 12'10"?

Doug
Current PJ: Optoma HD72
Current Screen: Carada 92" 16x9
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post #7 of 9 Old 01-26-2014, 11:33 AM
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It helps a lot when we've got all the details... wink.gif

Using the Epson calculator it looks like you're on the very edge of the minimum screen size of 105" at a throw distance of 12'10". The calculator doesn't deal with lens shift, so I can't tell from there what height the projector can be and still make it work. You're looking to mount the projector above the top edge of the image, so you'll definitely need to do some checking to ensure that's possible. The manual for the 5030 would be the best resource for that level of detail. And the "owner's thread" for the 5030 (there's got to be one in the Digital Projectors forum up a few from here) would be the best place to ask detailed, model-specific questions, too...

Jeff

Rock Creek Theater -- CIH, Panamorph, Martin Logan, SVS PB2000, Carada Masquerade, Grafik Eye, Bar table, Green Glue, JVC RS50 
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post #8 of 9 Old 01-26-2014, 11:44 AM - Thread Starter
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Thanks for the comments, and guidance, Jeff. And a major shout out on the pictures of your HT! That must have taken you a good long while to complete; the rich detail and aesthetic design are very impressive! I wish I had that size room to work with, but 15' x 11' x 8' is what we have and we're making the best of it.

Again, thanks!

Doug
Current PJ: Optoma HD72
Current Screen: Carada 92" 16x9
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post #9 of 9 Old 01-26-2014, 01:38 PM
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Thanks! Larger rooms suitable for home theater purposes (especially for those of us in geographies without basements) are hard to come by "accidentally". I had to build the house to get that space...

Rock Creek Theater -- CIH, Panamorph, Martin Logan, SVS PB2000, Carada Masquerade, Grafik Eye, Bar table, Green Glue, JVC RS50 
Theater build photos: http://photobucket.com/autor-ht

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