AVS Forum banner
Status
Not open for further replies.

Why do all projectors have offset throw?

910 views 11 replies 7 participants last post by  mdmaclean 
#1 ·
Why can't a projector shoot the image straight out its lens? It seems like all projectors must be either floor (or table) mounted or ceiling mounted. I would love a projector that would be placed directly facing the middle of the screen.
 
#2 ·
Quote:
Originally posted by ChaCha
Why can't a projector shoot the image straight out its lens? It seems like all projectors must be either floor (or table) mounted or ceiling mounted. I would love a projector that would be placed directly facing the middle of the screen.
I think it is just that this is what fits most people's setups and sells the best. If you want to spend more money then I think there are some options. For maybe $8k you can get close to the center with an SX21 that I've heard can go 40% of the way towards the center. The Sharp 10000 also has lens shift, but I don't know how much. Optoma is coming out with a $7k unit where the projector can go anywhere within the screen area vertically. I don't know how much play the Z1 lens offset gives you.


--Darin
 
#4 ·
Why I would want that is a good question. The answer is that I would like a projector that could be placed as near to the viewer as possible. With a retro-refractive screen like the Dalite HighPower, this is important. Since the viewer generally sits near the center area, I also want a projector that can accomodate. A ceiling mounted projector lens has to be above the top of the screen and a table mounted has to be below....all I want is one that can shoot straight.
 
#5 ·
The Sanyo Z1 can be placed somewhat near the center of a screen with the lens shift.


But even with a centered projector, you will still need a helmet mount for the projector. :)


Mark
 
#6 ·
ChaCha,


I put my M20x at the back of my room on a shelf upside down and use that with the Hi-Power, so I know the advantage of being able to do that. Since the viewer can get in the way I think a projector that could put maybe 20-30% of the image above the projector and 70-80% below would be about right. I think one rule of thumb is to put 1/3 image below eye level. It would seem like this setup would get you most of your brightness without the viewer getting in the way of the image, but it also depends on how far the throw puts the projector behind the viewer.


The HT1000 is the worst for this because the offset is just the opposite. I haven't gotten mine to play with, but I'm hoping to find a way to put the projector low on the wall. Tilting the screen out at the bottom a little bit can help with any keystoning issues from doing this.


--Darin
 
#7 ·
ChaCha-

Since a large percentage of projectors are ceiling mounted, the offset is required or otherwise part of the image would be projected on or blocked by the ceiling.


Also, don't forget the noise factor. Even the quieter projectors would be too noisy if they were too close to the viewers.
 
#8 ·
Quote:
The answer is that I would like a projector that could be placed as near to the viewer as possible. With a retro-refractive screen like the Dalite HighPower, this is important.
ChaCha, I understand your point. But if you think through it, you always can and want to place the projector at near the eye level of the viewer regardless of the throw offset, in order to have the optimal benefits of a retro screen. What changes in accordance with throw offset is the height of the screen, rather than the position of the projector.


In other words, as long as the viewers' eye level is at about 3 feet from the floor as usually is the case, you do want to have the projector placed as close to 3-feet high as possible, regardless of its throw offset. Given that, I am afraid that if the projector had a zero throw offset, then the screen would have to be placed way too low!
 
#9 ·
I have an X1. With the offset, this is what happens: table mount, the top of the projector roughly equals a bit below the bottom of the screen. Ceiling mount, the projector equals a bit higher than the top of the screen. Bottom line, you CANNOT place the projector within the screen without tilting the projector. This to me is not great when my 100' diagonal screen is 6 inches from the ceiling and 3 feet from the floor. Not a lotta wiggle room.
 
#10 ·
Quote:
This to me is not great when my 100' diagonal screen is 6 inches from the ceiling and 3 feet from the floor.
Um...? Sounds to me like a perfect situation. Why can't you place the projector upside-up on a tall table or stand (about 2 1/2 feet tall), so that the top of the projector is about 3 feet from the floor? Then the projector will beam approximately from the eye-level height of the viewers -- ideal for the High Power screen! Why is it undesirable???


[added in edit] ChaCha, you may be misunderstanding the optimal setting for the retro-reflective screen. You do not need or want to beam perpendicular to the center of the screen. What you need is to shoot from the direction of the viewers' eyes, who are, in your case, sitting well below the screen height.
 
#11 ·
I can't have the projector lower than 4 feet from the floor because of my room. My only concern is that this then leaves me with either ceiling mount (very high) or projector tiltage. The projector can't be vertically within the screen, which sucks for someone who has a small room and whose screen is their whole wall basically.
 
#12 ·
The Z1/1HD seems to fit your requirement. It can be placed anywhere between the top of the projected image, and the bottom of the projected image.


Its optical lens shift does just what you want!
 
Status
Not open for further replies.
You have insufficient privileges to reply here.
Top