Aligning Projectors

[HolyPhish]

Hello

 

I have to align two 5k projectors onto a single screen to double the brightness (the budget wouldn't stretch to a single 10k)

 

I know the basic theory of aligning them but I was wondering how u manage to get them to focus the same.

 

Also are there any time saving hints?

 

Thanks in Advance

[mac.calder]

Basically, use a grid test pattern, or a grid with circles in each of the 4 corners. Use lens shift to get the image in position, don't be tempted to angle one up slightly and one down. Avoid keystone and digital "mangling" of the image as much as possible.

[TomG]

There's a great video on the Nationals website about aligning projectors: http://www.nationaltheatre.org.uk/55591/vi...projectors.html Great Site, and a video with simple tips on the basics of stage lighting / sound and projection.

[David Lee]

Not really much help that video, very basic overview really.

[TomG]

Not really much help that video, very basic overview really.

 

It is basic but kinda shows the principle behind the alignment grids, and the use of multiple projectors.

[Johnparrack]

basically as the first poster says..: but

2 projectors isn't double the brightness in practice...usually about 60% brighter..contrast ratios and lamps etc etc dependant.

 

use a common grid, or even internal grid...I usually start with the internal projector grids for basic alignment, focus , zoom and to try and get both projectors optically aligned.

if you've got projectors with north south lens shift then its good to offset 1 up and 1 down, so they meet in the centre. don't forget the slightest skew on the projector in relation to the screen will and can make a huge difference. Also the type of lenses, long lenses are much easier as the lens shifts do more than with a shorter lens..then the 0.8, 1.2 wide angles tend to bow if not in the centre of the lens..

 

Once optically aligned, you can use a common grid from your source switcher, should you be using one for data sources...obviously "doubling for video images is much easier" than a high res double, as the accuracy isn't as important.

 

hth a little, its easy once you get used to it.

[David Lee]

It is basic but kinda shows the principle behind the alignment grids, and the use of multiple projectors.

 

Sorry, got to come back on this, but this vid only gives a very basic idea of aligning projectors.

 

Nothing about best methods of stacking and use of test patterns except the very basic line of "we use a grid to line two projectors up then turn on the next two." It is more about the fact that they blend and warp the projectors to a curved screen and is aimed at people curious about what goes on backstage rather than a tutorial on doubling projectors.

 

John and Mac give a much better description in a few words than the video does. I wonder if you've ever lined up one projector let alone doubled or blended them? Sorry to sound harsh but there you go.

[JazzAV]

These days Aligning Projectors should be pretty easy, I would just suggest that you spend a little time ensuring both units are well placed and straight on to the screen. If you are using front projection lenses then it should be pretty straight forward. As mentioned before its best to rig each projector off center and then bring them together (better to get both projectors to do 50% than expect 1 of them to do 100% of the work)

 

Don't use any geometry other than lens shift, spend your time getting the projectors level rather than relying on keystone etc.

 

Use internal grids to get both projectors square on the screen, don't jump straight to trying to double them up as it will probably start well, then you'll spend an hour wondering why 1 corner wont come in.

 

Rear Projection lenses can be more difficult as you don't usually have as much offset (very quickly the picture gets lost in the corners or distorts)

 

Number one Tip is get each projector square, level and straight on before you start, even if it means your rigging takes twice as long.

 

Also it goes without saying ensure that however you stack them (side by side or under over) that one projectors fan outlet is not being blocked by the other projector, or an outlet is being sucked straight into the other projectors fan, not really an issue with Barcos or christies but some of the cheaper makes haven't taking into account stacking.

 

Good luck with it, its very rewarding when you get a perfect line up.

 

Oh and of course it depends what you are projecting onto, if it is part of a set then, push the builders to ensure it is as straight and square as possible.

[Johnparrack]

Pm me for some help, more than happy, I've been in most scenarios and am willing to send pics of my shows to prove what I say...don't want to sound too big headed/pompous or just plain rude...but where doubles, trebles and soft edging is concerned I've been there and worn many a T-shirt.

 

 

 

A concurrent post has been automatically merged from this point on.

 

Sorry a quick addition, you adjust your projectors to the set/screen ...never works the other way round...usually screens are at least level, but bigger screens will bow and twist, and really theres not alot you can do...Experienced Projectionists just "cope" with it, and can offset errors so that they are not visible.

[DonkiDonki]

Sorry a quick addition, you adjust your projectors to the set/screen ...never works the other way round...usually screens are at least level, but bigger screens will bow and twist, and really theres not alot you can do...Experienced Projectionists just "cope" with it, and can offset errors so that they are not visible.

 

I usually find it best to get your projectors as square and level to the screen as possible and then correct that awkward bowing corner by adjusting the culprit stage brace yourself...

 

As John said, there will be times when you can't do anything about a warped screen, but it is still a good idea to check the state of the screen yourself before doing your line up. It will save you chasing your own tail and if the bow is too horrendous then something may have to be done with it.