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post #1 of 18 Old 07-01-2014, 11:04 AM - Thread Starter
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Lens Shift Question

So I'm having a bit of trouble wrapping my head around projector placement. I don't have a projector in mind since that's pretty far away, but since I'm trying to put the projector in the soffit in my HT build, I'm trying to get everything planned out before I put drywall up. If I can't put it in the soffit, then I need to plan projector placement hanging in the room somewhere.

My question is about lens shift. I'm using the Sony VPL-HW55ES for an example. In their manual they said you can have 71% vertical lens shift. What exactly does that mean? I can mount the projector up to 71% of the screen height above the center of the screen? or the top of the screen? I haven't ever set up a projector before so its a pretty noob question, I'm sure.

Basically, the screen size I'm looking at is 130" wide 2.39, 54" vertical. If I mount the projector 44" above the center of the screen (which puts it in the soffit, about 16" above the top of the screen), am I okay?

This also puts me at about a 17'-18' throw as well. Is this an acceptable throw for modern $3-5k projectors?

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post #2 of 18 Old 07-01-2014, 12:51 PM
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Quote:
Originally Posted by ClemsonJeeper View Post
So I'm having a bit of trouble wrapping my head around projector placement. I don't have a projector in mind since that's pretty far away, but since I'm trying to put the projector in the soffit in my HT build, I'm trying to get everything planned out before I put drywall up. If I can't put it in the soffit, then I need to plan projector placement hanging in the room somewhere.

My question is about lens shift. I'm using the Sony VPL-HW55ES for an example. In their manual they said you can have 71% vertical lens shift. What exactly does that mean? I can mount the projector up to 71% of the screen height above the center of the screen? or the top of the screen? I haven't ever set up a projector before so its a pretty noob question, I'm sure.

Basically, the screen size I'm looking at is 130" wide 2.39, 54" vertical. If I mount the projector 44" above the center of the screen (which puts it in the soffit, about 16" above the top of the screen), am I okay?

This also puts me at about a 17'-18' throw as well. Is this an acceptable throw for modern $3-5k projectors?
The 71% starts at the screen center. You could also say 21% of screen height allowed above the image. So for an image that is 54" high, you would have 11.34" of vertical lens shift. That is if you use zero horizontal lens shift. The two are tied together. A few things to keep in mind, the HW55 does not have lens memory, so if you want a scope screen, You need a Lumagen or an anamorphic lens or adjust manually. If placed in a soffit, manual adjustment is most likely out. Also, you never want to use all of the lens shift if possible. In other words, try to set the projector up, so that the lens center is at or close to top of image.

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post #3 of 18 Old 07-01-2014, 01:01 PM - Thread Starter
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Originally Posted by AV Science Sales 5 View Post
The 71% starts at the screen center. You could also say 21% of screen height allowed above the image. So for an image that is 54" high, you would have 11.34" of vertical lens shift. That is if you use zero horizontal lens shift. The two are tied together. A few things to keep in mind, the HW55 does not have lens memory, so if you want a scope screen, You need a Lumagen or an anamorphic lens or adjust manually. If placed in a soffit, manual adjustment is most likely out. Also, you never want to use all of the lens shift if possible. In other words, try to set the projector up, so that the lens center is at or close to top of image.
Hmm. Well that's not good news for my design ideas with enclosing the projector in the soffit. I don't have a problem with having 0% horizontal shift. 11.34" is not a lot to work with especially since my soffit would be 16" above the image... Hrm.... Wonder how other people do it.

I wasn't planning on buying the HW55, it was just one in the ballpark price of what I'm looking for, so I just grabbed the manual to see what the specs were for it for mounting and lens shift. Ideally I'd still be looking at a projector with lens memory & not outrageous input lag.

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post #4 of 18 Old 07-01-2014, 02:11 PM
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Different projectors have different ranges for lens shift/offset. Some have up to 100% (one full screen height), others must be kept within the screen area, it all depends. 16" on a reasonably large screen should be doable, but it will limit your projector choices.

See what an anamorphoscopic lens can do, see movies the way they were meant to be seen
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post #5 of 18 Old 07-01-2014, 04:16 PM
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the other thing is these specs are intended for a 16:9 screen. if you're using something with lens memory for a scope screen, that will complicate it even further as you're basically trying to use two different screen sizes from the same location.


honestly, I see a lot of issues with the idea of deciding where to mount before picking your projector.
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post #6 of 18 Old 07-01-2014, 04:50 PM - Thread Starter
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Quote:
Originally Posted by fierce_gt View Post
the other thing is these specs are intended for a 16:9 screen. if you're using something with lens memory for a scope screen, that will complicate it even further as you're basically trying to use two different screen sizes from the same location.


honestly, I see a lot of issues with the idea of deciding where to mount before picking your projector.
Interesting points, and yes, I agree. I need to figure out where to mount the projector and I'm nearing drywall time so this is why I started this discussion. To see if it was feasible to mount the projector in a location other than hanging from the ceiling.

So how do most people with scope screens handle this situation? With an anamorphic lens? Or just mount the projector closer to the top 20% of the screen?

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post #7 of 18 Old 07-01-2014, 05:33 PM
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Quote:
Originally Posted by ClemsonJeeper View Post
Interesting points, and yes, I agree. I need to figure out where to mount the projector and I'm nearing drywall time so this is why I started this discussion. To see if it was feasible to mount the projector in a location other than hanging from the ceiling.

So how do most people with scope screens handle this situation? With an anamorphic lens? Or just mount the projector closer to the top 20% of the screen?
it's usually best to aim for using no lens shift at all. if you make that your target, then adjusting a couple inches should rarely be a problem. if you plan on using most of the lens shift, you'll often be faced with placement issues in the end.


I'm running two screen now, a 120" I use for scope movies(pull down partway) and a 100" I use for 16:9. due to limitations in my room, both screens have their right edges in about the same location. my projector is mounted in a location that pretty much maxes out lens shift on the smaller screen. in fact, after mounting the projector where I thought I wanted it, I found out I could not get the image centred on the small screen. I had to drop it several inches in order to use less vertical shift, and free up more horizontal shift. after doing all this, I think I was just lucky that the big screen also worked. haha.


but if you can put the projector in a spot where it uses no lens shift, then going back and forth between lens memory settings should be easy, and only limited by the zoom range.
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post #8 of 18 Old 07-01-2014, 06:21 PM
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Quote:
Originally Posted by fierce_gt View Post
the other thing is these specs are intended for a 16:9 screen. if you're using something with lens memory for a scope screen, that will complicate it even further as you're basically trying to use two different screen sizes from the same location.


honestly, I see a lot of issues with the idea of deciding where to mount before picking your projector.
It is still based on screen heigh. With any of the LCOS, SXRD or LCD projectors that have lens shift, as long as he just uses the height of the image, it will work for any scope screen.

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post #9 of 18 Old 07-01-2014, 06:24 PM
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Quote:
Originally Posted by fierce_gt View Post
it's usually best to aim for using no lens shift at all. if you make that your target, then adjusting a couple inches should rarely be a problem. if you plan on using most of the lens shift, you'll often be faced with placement issues in the end.


I'm running two screen now, a 120" I use for scope movies(pull down partway) and a 100" I use for 16:9. due to limitations in my room, both screens have their right edges in about the same location. my projector is mounted in a location that pretty much maxes out lens shift on the smaller screen. in fact, after mounting the projector where I thought I wanted it, I found out I could not get the image centred on the small screen. I had to drop it several inches in order to use less vertical shift, and free up more horizontal shift. after doing all this, I think I was just lucky that the big screen also worked. haha.


but if you can put the projector in a spot where it uses no lens shift, then going back and forth between lens memory settings should be easy, and only limited by the zoom range.
Very hard to mount many of these projectors at zero lens shift, since with most of the LCD, LCOS and SXRD projectors, zero shift point is dead center of the screen.

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post #10 of 18 Old 07-01-2014, 06:48 PM
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Not sure if it helps, but I just took some quick measurements. With my JVC RS4810 and 2:35 screen (46"x108") the center of the projector lens is mounted about 5" above the top of my 2:35 screen. However, horizontally it's a good 20" from the center of the screen, but no issues at all. I use the zoom method and do not have an anamorphic lens. It works beautifully.

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post #11 of 18 Old 07-01-2014, 08:59 PM
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Originally Posted by AV Science Sales 5 View Post
It is still based on screen heigh. With any of the LCOS, SXRD or LCD projectors that have lens shift, as long as he just uses the height of the image, it will work for any scope screen.
but the image height will still be 16:9 'spilled over' the scope screen. so it's a little less straightforward, and he may have to consider that. I think most of the time it'll work if the 16:9 full screen image fits, as zooming in for scope and raising the top edge of the image above the screen would likely mean less shift is needed. but I'm not sure that's always the case, that's why I mentioned it
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post #12 of 18 Old 07-01-2014, 09:06 PM
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Very hard to mount many of these projectors at zero lens shift, since with most of the LCD, LCOS and SXRD projectors, zero shift point is dead center of the screen.
totally agree, and I've never been able to get close myself. but both projectors I bought I had planned on using lens shift, and both times I had to reposition them because I was counting on it. even with the jvc, I thought I was going to be way inside the lens shift, and then when I put it up, I couldn't get the image centered. I had plenty of horizontal range, and I had plenty of vertical range, but when I needed both it wasn't there. they do clearly say the lens shift is reduced if using both, but not by how much. I was surprised that using a little bit of the vertical shift reduced the horizontal shift by so much, and vice versa. I only needed about 50% of what was advertised, and it wasn't there.


so, for any newbie(which I still consider myself to be closer to than a pro), I think it's risky to plan on the lens shift. being able to have no horizontal shift is a great start, but even with that I'd advise he not count on using more than 75% of the specified vertical shift. just in case. maybe he needs to shift the image an inch or two horizontally due to some small miscalculation or aesthetic decision. that might be enough to reduce the vertical range to a point it becomes an issue.
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post #13 of 18 Old 07-01-2014, 09:50 PM - Thread Starter
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Thanks for all the help and responses guys. I'm in the process of rethinking how all this works out. The 16" above the screen in the soffit is obviously not going to work.

I've been reading a bit about the Lumagen Radiance Mini 3D -- wondering if this will help me out a bit. At least it would free me from just looking at projectors with lens memory and open up some other projectors that would be good for movies and games rather than just one or the other.

Stinks that I'm so far away from figuring out which projector to buy but I'm at the point where I have to at least figure out where placement is because I'm almost to soundproofing the room and I need to have it all figured out before I hang my double drywall and green glue.

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post #14 of 18 Old 07-02-2014, 04:36 AM
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Quote:
Originally Posted by fierce_gt View Post
so, for any newbie(which I still consider myself to be closer to than a pro), I think it's risky to plan on the lens shift. being able to have no horizontal shift is a great start, but even with that I'd advise he not count on using more than 75% of the specified vertical shift. just in case. maybe he needs to shift the image an inch or two horizontally due to some small miscalculation or aesthetic decision. that might be enough to reduce the vertical range to a point it becomes an issue.
As long as you plan to mount the projector centered on the screen horizontally (which is always a good idea), you'll be fine as long as you don't plan on using the extremes of lens shift.

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post #15 of 18 Old 07-02-2014, 05:51 AM
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Originally Posted by fierce_gt View Post
but the image height will still be 16:9 'spilled over' the scope screen. so it's a little less straightforward, and he may have to consider that. I think most of the time it'll work if the 16:9 full screen image fits, as zooming in for scope and raising the top edge of the image above the screen would likely mean less shift is needed. but I'm not sure that's always the case, that's why I mentioned it
Sorry, I meant to say the height of the screen's viewing area.

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post #16 of 18 Old 07-02-2014, 05:55 AM
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Quote:
Originally Posted by ClemsonJeeper View Post
Thanks for all the help and responses guys. I'm in the process of rethinking how all this works out. The 16" above the screen in the soffit is obviously not going to work.

I've been reading a bit about the Lumagen Radiance Mini 3D -- wondering if this will help me out a bit. At least it would free me from just looking at projectors with lens memory and open up some other projectors that would be good for movies and games rather than just one or the other.

Stinks that I'm so far away from figuring out which projector to buy but I'm at the point where I have to at least figure out where placement is because I'm almost to soundproofing the room and I need to have it all figured out before I hang my double drywall and green glue.
You can make it work. You just have to know all the facts and set everything up. A JVC has 30% vertical above the image lens shift, so with your screen, you are looking at 16" of vertical lens shift. Move the screen slightly higher on the wall and you have a working solution. Personally, I would mount the projector lower, but that may not be what you want.

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post #17 of 18 Old 07-02-2014, 01:57 PM
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As long as you plan to mount the projector centered on the screen horizontally (which is always a good idea), you'll be fine as long as you don't plan on using the extremes of lens shift.
yeah, that basically what I meant. if you don't plan on using ALL the lens shift, you have room for a little error. it's just that sometimes how much room for error you think you have, is not the case.


with my jvc, I thought I had a lot more room than I did. I didn't realize how much using the vertical shift would limit the horizontal shift. which is why I'd say it's best to not plan on using more than 50% of the rated shift unless you know for sure you can have it perfectly centered.
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post #18 of 18 Old 07-02-2014, 04:02 PM
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Consider mounting the projector first. I know that is not what usually happens. Then install the screen to suit. Just use the wall temporarily. Remember that if the screen is closer to the projector than the wall (a virtual certainty) that image will be a bit smaller. Try it and live with the mock up a bit. I find I see things a week later that escaped me at the outset. If it were me, a four theater refugee, I would put the projector on a step ladder rather than thinking I could mount the bracket first shot. All IMHO of course.
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