# Qlab, blackmagic and blended projectors - Oh My!



## gwpac (Jan 7, 2016)

Hey theatre bods,
we are just about to buy a bunch of equipment in order to give us full cyc projection. Given the geometry of the place, this is only possible via two edge blended projectors.

The second hurdle is the ability to play any walk-up client's (we are a multi-use space) video/powerpoint/photostory or whatever - with no training time. 

So this brings us to our solution, and I just want to see if anyone has done anything similar or if anyone has any tips.

Input: VGA & HMDI to HDBase-T (we've been happy with HDBase-T, and already have the Cat6 runs)
-> BlackMagicDesign Ultrastudio 4K
-> iMac 5k Retina via thunderbolt cable
-> Qlab where we do some surface stuff to either fit, crop or stretch the inputs to the full surface which will be about 3800 px x 1200 px, and some edge blending.
Output: via thunderbolt cable to:
-> matrox Dualhead2Go ME
-> outputs two DVI-D
-> DVI-D to HDMI cables
-> HDBase-T transmitters
-> Projectors

Anyone had any experience with any of these steps and confirm my hopes?
Cheers!


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## Chris15 (Jan 8, 2016)

Is this going to be permanently installed or deployed on a show basis?

Edge blended projectors are a major source of pain for us as a university. The moment the projector moves, the blend is out. Change a lamp, it's gone.
In one of our spaces, just getting the projectors up to full operating temperature causes enough movement to throw off the blend...

The mechanical side of mounting is critical. The mounts will need to be exactly positioned to project dead perpendicular, keystoning is totally out, and anything more than minor lens shifting will cause issues too...

We generally do the edge blending in the projectors themselves, Panasonic PT-DZ770 or PT-DZ870s rather than in software...


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## gwpac (Jan 10, 2016)

Chris15 said:


> Is this going to be permanently installed or deployed on a show basis?
> 
> Edge blended projectors are a major source of pain for us as a university. The moment the projector moves, the blend is out. Change a lamp, it's gone.
> In one of our spaces, just getting the projectors up to full operating temperature causes enough movement to throw off the blend...
> ...



Thanks for your reply.
Yes it's going to be a permanent install on fixed bars that are rarely accessed - so hopefully they won't get any bumping or bouncing.
Your comments about not being able to keystone and lens shift is causing some concern though! I've spoken with the manufacturer and they have assured me people do it - nevertheless, I know it's going to be a bit of a bear to get right.
Do you do all your blending in projector? We will have blending and geometric correction options further up the chain, via Qlab and the DualHead, so hopefully we will be able to correct issues more readily than you have been able to.

I'm curious if anyone has used any of the blackmagic gear?


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## ruinexplorer (Jan 11, 2016)

I don't know if Panasonic has made some improvements in the last few years, but I used to have significant lens drift with their PT series. I absolutely love the simplicity of their projectors and the quality of image they produce, but whenever it was needed to stack or blend, they were a pain in the ...

That being said, when you have a permanently installed system that is edge blended, don't believe that you can just come in, turn it on, and it will be ready to go. You will always need to allow the projectors to come to temperature (not just the lamp) and may need to make some adjustments. Depending on the environment they are in, I would generally give them about 30 minutes. Essentially you want to make sure that the entire optics train and lens mounts are at their operating temperature before making adjustments.

Yes, you can blend a keystoned image, but it will be more of a challenge and can diminish the quality of the image. I don't know if that model projector has edge blending capabilities, so you may need to stick with Qlab. Make sure that you don't bog down your system with too many variables. 

Honestly, there are a lot of variables at play when edge blending. You will need to color match your projectors as well as balance for "brightness" for a quality image. All of these things take time and make it less and less of a viable drop in system.


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## gwpac (Jan 11, 2016)

You guys are scaring me!
We are using epson projectors for what it's worth. We've been very happy with them in the past.
The big factor in our favour is that this will be a very large image seen from very far away - the closest anyone will be sitting will be about 12 metres - (about 39 feet). So I guess if it's a little blurry, it won't be too noticeable.
We will always have plenty of time to warm up the system before use, so that's not a problem.
But I guess there's still no guarantee that we won't be tearing our hair out tweaking the system constantly. I do hope not.
It's going to be permanently installed for at least the next three years, and won't ever need to be shifted or changed or used for anything else - so that's in our favour.
Just hope this isn't going to be an expensive waste of time.


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## Chris15 (Jan 12, 2016)

What are your fixed bars fixed to?
And how are they attached?

We're on individual mounts for each projector affixed to the ceiling slab in most (though not all) cases - side note, if anyone every tries to convince you edge blending projectors mounted on separate lifting mechanisms is an idea, RUN!

We are dealing with a different set of performance requirements - we need to have a spreadsheet or website acceptably readable in the blended area, which is a challenge and really needs every pixel in the blend to line up, hence why keystoning, lens shifting, anything not square really causes issues.
Note also that in general we have a zero tolerance for digital keystoning on our installed systems, the moment you start digitally altering the image, you're losing resolution by the pixels that are getting trimmed for keystoning and that is problematic in some of our use cases...
Again, in a production context for background imagery this may not be an issue...


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## gwpac (Jan 12, 2016)

They are fixed to the I-Beams and concrete slabs of the roof and wall structure - so pretty solid. We haven't bought the mounts yet, but I'm imagining they will be on plates that are scaf-clamped onto the bars.

Ah yes - we did have a stacked projector system in another area that were on individual dropper poles at least six feet long and they were at least that far apart as well. The image for that was like yours lots of text, spreadsheets and documents, meant to read from close - essentially a large classroom size. Anytime the airconditioning turned on, the screen would move a little, which meant the stacked images would drift apart due to their different directions they came from. Also the dropper bars would shift over time due to aircon, building movement - anything. Ended up getting it replaced with a single brighter machine.

This current system we are talking about is as you say - background videos for productions generally. So not as pixel-critical as your situation. Plus the fixing points are going to be a lot more rigid.


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## WVTheatre (Jul 17, 2016)

I recommend a single projector for anything projected onto a cyclorama for example. We have a very bright Panasonic projector with a long-throw lens at our FOH position, which is above everyone's heads, and I will say it looks phenomenal. It cuts through haze and some stage light pretty well. I would only use two projectors for projecting the same image side by side, or for two different images.


Sent from my iPhone using Tapatalk


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## ruinexplorer (Jul 17, 2016)

The nice thing about projecting on a surface such as a cyclorama is that it is a low gain surface. Blending two or more projectors works best on low gain surfaces as it allows you to not see the blend area from wider angles. The higher the gain, the easier it is to see the blend.


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