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Zooming CIH and projector mounting distance/offset question ...

642 Views 2 Replies 2 Participants Last post by  schmittmj99
Hello there,

I have been doing research now for a couple of weeks in an attempt to convince the wife that we need a front projector system downstairs in our family room. After reading a bunch I still have a couple questions, and in order to have the best luck in realizing this dream, I figure I should present my argument with everything figured out exact.

So ...

In an effort to keep costs down (for easier convincing) I have decided that I will be doing a DIY painted screen wall. Due to this I think that I could see some benefit to immersion by running with a CIH setup using manual zoom (for now, gotta start somewhere right ... ?). My question is, when determining where to mount the projector which screen size charts (per projector user manuals) should I be going off of?


I am looking at a CIH of 44" - 49" (to fit my wall and speaker placement). This gives a 16:9 size between 90" and 100 diagonal" and a 2.35:1 size between 112" and 125 diagonal".

I am considering a Mitsubishi 7900DW and according to the user manual ( http://www.mitsubishi-presentations.com/wp-content/files_mf/hc7900dw_manual.pdf pages 10 and 11):

"When the aspect ratio of the screen is 16:9" ...

IH: 44" ... Throw: 108" - 162" ... Offset: 15" ... Lens Shift: 6"

IH: 49" ... Throw: 120" - 180" ... Offset: 16" ... Lens Shift: 7"

(Note: This seems like it could be used with a "set" 16:9 image then zooming OUT to get to 2:35:1, according to the pictures from the manual)

"When the aspect ratio of the screen is 2.35:1" ...

IH: 44" ... Throw: 142" - 213" ... Offset: 26.4" ... Lens Shift: 8.2"

IH: 49" ... Throw: 160" - 239" ... Offset: 29.5" ... Lens Shift: 9.5"

(Note: This seems like it could be used with a "set" 2.35:1 image then zooming IN to get to 16:9, according to the pictures from the manual)

Now that is a big difference in Throw and Offset between the two aspect ratios. When deciding on where to mount the projector which chart would I go off of? If I have things figured out correctly, even though my screen would be 2.35:1 I would be best off figuring my mounting for the projector using the 16:9 chart and then zooming OUT to fill the 2.35 area as this allows a closer throw and more brightness.

I am understanding all of this correct?

Any help would be appreciated, thanks in advance.

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I'm a little confused with all that myself.

For zooming back and forth from 2.35:1 to 16:9, you really need a projector with lens shift, which it appears the Mitsubishi does not have. Zooming from 16:9 to 2.35:1 usually means that the image will shift up or down on the screen as well as grow larger. Without lens shift there is no way to account for this (at least, without building some kind of adjustable offset mount!) This would account for the differences in the offset specifications.

So, your options are to leave it either zoomed to 16:9 OR 2.35:1. If you leave it zoomed to 2.35:1, your 16:9 image will project above and below your painted screen area - UNLESS you buy a scaler like the Lumagen that will allow you to scale 16:9 to fit inside the 2.35:1 area (which entails quite a bit of resolution loss).

My suggestion? Go with a projector that has lens shift if you want to zoom, or add an anamorphic lens to the Mitsubishi and mount it as suggested for 16:9 (the lens does the rest).
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Thanks for the reply John.

I checked again and the Mitsubishi does have Lens Shift (and a large offset). I have also considered a couple of refurbished, used, or B-Stock models such as a Panasonic AE-8000, Epson 8350 or 8700UB, and the Sony HW50ES. The price of the Mitsubishi 7900DW is its biggest feature here though to try and get something done.

You did ultimately answer my question though, in that when using the zoom method you mount for 16:9 and not for 2.35:1 and can use a calculator either on the manufacturer website/manual or projectorcentral to aid with this. In essence with the zoom you are still displaying a 16:9 image, just masking off a portion of it. I think it is all making sense now.
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