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some ideas please on where to mount

av addict

Active Member
hi i am very close to buying hd72i for my new hd-a1 thats coming today--
anyway because the proj needs to be in the centre of screen we have a light
fitting smack in the middle of were i need to place it--light drops about9inces
so would i be able to mount the proj about 10inces down on the wall on top
of a shelf,it would give it a clear path then to my screen--would this affect picture performance---cheers
 

Oakleyspatz

Well-known Member

av addict

Active Member
cheers m8 for your reply--is there a rule of form to say how high this shelf
has to be--
 

kdr1066

Standard Member
I'm not sure of the technical term, but the HD72i does raise the picture by [I think] 1.5 inches per foot of throw distance, so you'd need to use the adjustment (not quite sure how much there is available) if you mount 10" down from the ceiling to clear the light fitting (otherwise you'll be projecting back up on the ceiling). I've seen posts saying it's better to avoid using these shift adjustments if you can as picture quality is compromised, albeit I expect only slightly. You might be better off getting a wall mount and inverting the PJ. Alternatively, a low rear shelf.

I have a 72i which I sit on small cabinet, about 18" or so off the ground, but it's a temporary arrangement until I decide on a more permanent solution, and the picture is quite high up at the mo' (but screen hanging is another issue for me :rolleyes: ) .

If you're hoping to shelf mount behind the sofa like Oakleyspatz I think you'd need to use quite a lot of shift with the 72i. I'm no expert though, just something for you to check, good luck :smashin:

BTW the 72i is excellent :)
 

av addict

Active Member
looks kind smart that--suppose i would have to hang it upside down thou-would this be a problem--

cheers for your replys:smashin:
 

bravogolf

Active Member
sparkytoon said:
looks kind smart that--suppose i would have to hang it upside down thou-would this be a problem--

cheers for your replys:smashin:
You mean hang the projector upside down? If so, that shouldn't be a problem. Most, if not all, projectors allow the user to select the mounting position. So, for example, I hang my upside down Z4 off that mount linked to above and I select Wall Mount from the Mounting Position in the options. This turns the image back around again :thumbsup:
 

av addict

Active Member
so one more question please--ideally then where does the projector need to
be pointing at the top or middle considering the screen i want has a big black
border at the top as well---even thuo i can't mount this on the ceiling
the pj will be aligned with the top of the screen under the big black border--

hope this makes sense lol
 
K

Kadders

Guest
sparkytoon said:
...the pj will be aligned with the top of the screen under the big black border
The word 'aligned' worries me a bit here! ... As mentioned above, the HD72i has a large offset, so the lens centre will be some way above the top of the screen if mounted upside down (ie. ceiling mounted), or below the bottom of the screen if it's the right way up. The offset will probably mean that projected light would miss your light fitting, without you having to mount the pj lower than the fitting!

A question for you! Is this light fitting the reason you say you cannot ceiling mount the HD72i? If so, and you'd really prefer ceiling mounting, how far behind the light would the projector be? I bet it's not in the way really!

To work out the offset, use this formula (from Optoma web site):
H' = L * tan(6.52), where L is the distance from the pj to screen

So for a 10 ft throw, Offset= 120" * tan(6.52) = 13.7"

(As tan(6.52) is a constant, the formula is more easily expressed as H = L x 0.1142)

This means that if it's ceiling mounted, upside down (you tell the pj it's ceiling mounted in a menu setting - very easy!), the centre of the lens will be 13.7 inches above the top of the projected image, when the front of the lens is 10 feet from the screen. This assumes that the pj is not tilted, of course! You'll need to work out where the bottom of your 'big black border' will be, and work the offset from there.

One other thing - horizontally, you need the centre of the lens to be central to your screen. Note that the lens is not at the centre of the projector! You need to take all of the above into account when you mount it.

I have yet to ceiling mount my HD72i, and the offset is such that I have it on a very low table (less than 2ft off the floor) and the bottom of the image is nearly 4 ft above the floor.

The offset is significant, but can be helpful (as in your light fitting - depending how far behind the light you can mount the pj). For instance, you say your light fitting has a 9 inch drop... If the pj lens was 5 ft behind it (assuming the fitting is centrally in your room), the lens could be just 2 inches below the ceiling and still miss it! It is actually impossible to mount the pj that high, because you have to fit the base of the HD72i at least 10cm away from the ceiling (the base will be at the top!) - this is a recommendation in the manual, to allow air flow. The lens is also more than 2 inches way from the base. So unless your light is very close to the pj, ceiling mounting is no issue.

Feel free to pm me if you want to discuss this further - by phone if necessary.
 

av addict

Active Member
To work out the offset, use this formula (from Optoma web site):
H' = L * tan(6.52), where L is the distance from the pj to screen

So for a 10 ft throw, Offset= 120" * tan(6.52) = 13.7"

(As tan(6.52) is a constant, the formula is more easily expressed as H = L x 0.1142)

cheers kadders--i wish i listened in maths at school now:confused: i'm kinda
getting the idea just have to read it a few more times to get it to sink in:D
i'll have another look later when the little ones not running about

cheers m8
 
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