[TexRob]

I have not found anything here or on the net real great. Just using my basic deductions from the very cryptic manual diagram for the Optoma HD70 I just ordered, I think it's this. Basically, they are designed for zero keystone position to be the image beginning completely level with the projector bottom. So for a 45" tall image (92" diagonal screen), with an 8 foot high ceiling with the projector mounted 7 feet off the ground (upside down, is that correct?) then the bottom edge of the screen would need to be 39 inches off the ground. Is my math right? I guess I always assumed these worked like the projector would need to be dead center, apparently that is incorrect.


Any tips or corrections are appreciated. Kind of surprised there is not a stickied thread here for "Dummies guide to projector and screen mounting". Plenty of distance calculators, but not much explaining the basics of how to mount and set up to avoid keystoning, which I refuse to do from all I have read.

 

[bud16415]

TexRob


All projectors are different and have a specific set of limitations as to where you should place them and how much range you have within that location.


The basics are they are designed to ether be table mounted or ceiling mounted and when ceiling mounted they should be inverted and then the image flipped within the menu. The menu will allow you to flip the image 4 different ways top to bottom and right to left. Those settings are for both front and rear projection and table and ceiling in both modes.


You are right the image comes out of the lens at a angle and slants down and the optics in the projector are set up to account for all that. If you were to say mount a projector at the ceiling and not flip it over it would shoot the image to the ceiling. If you then tilted it down to find the screen you would then need to use a huge amount of keystone.


Along with this different manufactures and different models have different amounts of drop height and focal distance and zoom capabilities. Some are better suited to low ceiling rooms and some high ceilings. The close you match up the height to the middle of the spec the less keystone you will use and the best PQ is zero keystone. But many use it and with movie content it's hard to tell. Graphics are a different story. Throw length is another factor and zoom. And zoom has a real effect on brightness. Some people use zoom also as a way to view scope movies (widescreen size) as a constant height. That's a bit more advanced but something that you may or may not care about.


Then there is the ability of some projectors to shift the image. Some do and some don't. some have shift up and down and some side to side also. Some limit the side to side based around how much up and down is used.


You have to do both a search of the manufactures web page for the details for a specific projector and also projector central . com has a good calculator for this. plus the information that comes with the projector. On the forum most of the projectors have one or more threads running and once you narrow down the projector then go there to find info on the correct screen and tweaks.


There is a lot to consider when selecting a projector all the above and things like lumens and CR plus screen size and room lighting. All this done correctly can give an outstanding PQ. But I know what you are saying it is really confusing at first.


I hope something I just typed helps you and others somewhat. And I'm sure many others will post in with info on your projector specifically.

 

[TexRob]

Thanks so much, it was very helpful. I thought I had figured it out, but I just kind of needed someone with a lot more knowledge than me to confirm it

I am pretty happy with all I have ordered. I think for my khaki walls, and overall generally pretty light furniture, the .9 gain grey screen was the way to go. We do have plantation shutters in the room though, so we should be able to block light out very well when we need to. I have full control over screen and projector mounting though, as far as placement, so I should be good to go.


One last question. Is it better to mount the projector closer if you are able to, if using a grey screen? Seems to me closer = brighter, and brighter = better contrast and brightness with a grey screen. I will be projecting onto a 92" screen, and I think the optimal mounting is about 10-12.5 feet.

 

[bud16415]

Here is the review and a few good pointers.

http://www.projectorcentral.com/optoma_hd70.htm


The zoom range isn't enough to see a difference in this case. I would shoot for right in the middle and only shift it if there was a mounting problem at that location. Remember you need to put the centerline of the lens on the centerline of the screen.


Here is how I did mine.

http://www.avsforum.com/avs-vb/showthread.php?t=846744


Good luck sometimes all we need is reassured that we are on the right path. Enjoy and post back how things work out. Screen and room sound about right to me also.

 

[TexRob]



Quote:
Originally Posted by bud16415 /forum/post/0


Here is the review and a few good pointers.

http://www.projectorcentral.com/optoma_hd70.htm


The zoom range isn't enough to see a difference in this case. I would shoot for right in the middle and only shift it if there was a mounting problem at that location. Remember you need to put the centerline of the lens on the centerline of the screen.


Here is how I did mine.

http://www.avsforum.com/avs-vb/showthread.php?t=846744


Good luck sometimes all we need is reassured that we are on the right path. Enjoy and post back how things work out. Screen and room sound about right to me also.

Explain to me what the centerline is exactly if you could. I assume that means the center line of the image, not the centerline out horizontally from the middle of the screen to the middle of the lense? I just want to make sure.

 

[bud16415]

Ya know I typed that and I thought I hope he doesn't think I mean from the center of the screen. Sorry for that you are correct. I mean centerline right and left across the room on the center of the screen.


Your projector mount will have front facing tilt up and down and side tilt to get the image level. It might have some drop height adjustment to move the whole projector up and down. And of course you have the keystone adjustment in the projector. What most of these simple mounts don't have is side to side and people do a rotation on the drop tube to move the image right and left. Doing that is not the best IMO you can get away with a little of that and I did for a year with my old mount but after making the slider mount I found the edges of the image were much easier to control when I actually have the lens dead on center of the screen and the drop height right the image is very square (no bowing). The best way to find center is run a string of the same length from each corner of the screen to the lens. Equilateral triangle. If the center of the lens is right and the image is off the screen left or right you then know you have twist.

 

[TexRob]

It seemed to me the easiest way to go about this was to of course measure and mount the projector dead center, but mount it first, then project the image onto the bare wall, and use that as a rough guide for my hanging of my fixed screen, that and measurements, etc. The screen can always get rehung, much easier than moving the projector mount.


Is that how you and most people do it?

 

[bud16415]

That method works for me also. Thing is if when you project to the wall your projector is say 1 degree out of being square to the wall and its 144 from the wall. If I remember right a degree is about .015 inches so .015x144= 2.16 inches. So it's not that hard to be an inch or two off the square mark. It may never be noticeable to you. When the image strikes the screen at any angle other than 90 the one side will be slightly taller than the other by a small amount. Most people let that small amount spill over into the border and it eats the little sliver of the image.


There are numerous tricks if things don't work out perfect some people tilt the screen a slight amount from top to bottom if they cant get the drop height right because of ceiling height or mount isn't the right drop. You can also kick one side of the screen out a smidgen.


Everyone has a different level of fussiness when it comes to setup. I'm not super fussy but I'm lazy so that's part of the reason I tried this new slide thing. That and it's a way to bridge over to get into something solid in the ceiling.