Projector mounting - inverse vs shelf

[justin-ni]

Hi guys,

I've tried searching online for an answer here, but I'm not having much luck!

I notice that most people have their projector inverted when positioned above screen height. When against a wall, and a shelf is availble, is there any disadvantage to mounting the projector the 'correct way up' or does inverse mounting add benefit to ceiling height installations?

Thanks in advance,
Justin

[DrugstoreCowboy]

Projectors fire the image up and forwards toward the screen so if it's placed on a shelf high up and it's not inverted you'll end up with an image projected higher than projector is mounted, probably spread across your ceiling.

^^^ It's not a great example but you get the idea.

[jacko5]

Originally Posted by justin-ni

Hi guys,

I've tried searching online for an answer here, but I'm not having much luck!

I notice that most people have their projector inverted when positioned above screen height. When against a wall, and a shelf is availble, is there any disadvantage to mounting the projector the 'correct way up' or does inverse mounting add benefit to ceiling height installations?

Thanks in advance,
Justin

If you prefer to mount your projector on a high shelf right way up, as I do, then you will need a PJ with vertical lens shift.
My Sharp XV-Z21000 is mounted on a shelf with the centre of the lens a few inches below the top of the screen. I then use lens shift to exactly fill the projection area of the screen.
The lens shift feature is most common on LCD and DILA PJs and quite rare on DLP projectors in the lower price range.

[justin-ni]

Excellent, thanks guys - makes sense now.

I was concerned becuase the PJs I was looking at (X10 & HD800X) do not have lens shift, and I hear that keystoning the picture reduces resolution & can introduce artifacts?

Looks like I need to give alot more thought to the mounting postition of the PJ. I read on a post elsewhere that the X10 should be 36% higher than the screen height to avoid the need for lens shift / keystoning. Is this figure generic to all PJs, or just those of identical throw?

Thanks again,
Justin

[Pecker]

Originally Posted by justin-ni

Excellent, thanks guys - makes sense now.

I was concerned becuase the PJs I was looking at (X10 & HD800X) do not have lens shift, and I hear that keystoning the picture reduces resolution & can introduce artifacts?

Looks like I need to give alot more thought to the mounting postition of the PJ. I read on a post elsewhere that the X10 should be 36% higher than the screen height to avoid the need for lens shift / keystoning. Is this figure generic to all PJs, or just those of identical throw?

Thanks again,
Justin

Justin, yes keystone reduces resolution a little , but it should not introduce artefacts. Artefacts are introducing in the scaling process when an image has to be upscaled, and the PJ has to 'guess' what to put in the 'missing' pixels...and gets it wrong. This does not happen when you downscale, and vertical keystone only downscales - it doesn't upscale.

Subsequently you should see no more artefacts when using keystone than you would using a 1080i/p broadcast/disc on a 720p/768p display. So far, as far as I can tell, no one has ever reported a downscaling artefact - just loss of resolution.

On the resolution front, the loss should be quite small. You might want to read this thread, particularly the last post (#26).

A couple of notes of caution.

Firstly, if you place a PJ the right way up, but on a high shelf (as high as if it were hanging from the ceiling) you may find the distortion of the image (from a regular rectangle to a trapezium) is so great that your PJ doesn't have enough keystone to deal with it.

Secondly, presuming your PJ can handle the amount of keystone needed, whilst the picture might fit the scren, the PJ will still be projecting a 'black' trapesium, and the black triangles at the edges won't actually be black at all(just a very dark grey. This may or may not distract you whilst viewing.

You might want to check out posts 10, 11 and 12 out on this thread.

Steve W

[cyberheater]

I've had quite a few DLP projectors with a fixed offset and have mounted them upside down resting on a couple of shaped wooden blocks on a rear mounted high shelf. It's easy and it saves having to find a load supporting beam in the ceiling.

[enablerbro1]

Before I really looked into PJs I had planned to mount on a shelf but once I discovered the screen size created from what would have been the throw distance I had to rethink and ceiling mounting became the only resonable option.

[cyberheater]

Originally Posted by enablerbro1

Before I really looked into PJs I had planned to mount on a shelf but once I discovered the screen size created from what would have been the throw distance I had to rethink and ceiling mounting became the only resonable option.

Yes. It's a pity that you can't buy projectors (especially DLPs) with a choice of short or long throw lens. I much prefer to have my PJ mounted on a shelf rather then have it sitting dangling from the middle of the ceiling. Plus the hassles or routing cables etc... for a ceiling installation etc...

[imjay]

From the beginning we've had our projector on a shelf approx. 5ft. above the floor with ceiling height of 7 3/4 ft. with a 11 1/2 throw distance and it works outstanding.

Our fixed wall screen frame is flush with the ceiling so screen surface begins about 4 inches down.

We did have to do a bit of keystone adjusting with our first projector but we couldn't see any image degradation.

Now we have a Panasonic LCD with a ton of vertical and horizontal lens shift capability.

Both consumer DLP (single chip with the spinning wheel fix for only a single ship) and LCD technologies have evolved to be very competitive with one another so our experience is that LCD looks every big as good as DLP without the possibility of a viewer suffering from RBE and the image throw flexibility of lens shift and usually better zoom.

[Gruntfuttock]

I've got mine fixed under a beech board which inturn is fitted to the wall by shelf brackets on the top which are boxed in beech, proper DIY job. It's 7ft from the ground, the centre of the screen is exactly the centre of the lense. I don't know if dead centre gives the best picture, I'm no expert, but it seems to work well.
As Cyberheater says it also helps with cable runs etc, I've chased mine into the wall, the ceilings are 11ft high so the idea of running them up there would be a nightmare, also I can easily reach it to focus etc.

[MIB]

Originally Posted by cyberheater

I've had quite a few DLP projectors with a fixed offset and have mounted them upside down resting on a couple of shaped wooden blocks on a rear mounted high shelf. It's easy and it saves having to find a load supporting beam in the ceiling.

I'm thinking of placing my Planar 7010 inverse on a high shelf but as the top is curved was wondering what to place it on. Did you make the wooden blocks yourself - can you post any pics please?