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Help! LED screen to true blackout

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Hi All, 

I'm new here and in need of some help.

I'm currently working on a Cruise Ship and we're installing some new shows. I'm having a little bit of an issue where we have an LED wall upstage and 4 LED screens that move on and off the stage via tracks. 

My issue is when we're doing a blackout there is still a glow on all screens so it's not a true black out.

Tech-wise, we're running QLAB to a data path for the 4 screens and for the LED screen it's QLAB to a Videotel (Nova Star) and down to the screen.

I've tried running a black masking under all the QLAB cues. The desktop is also black on all the extension screens too. I'f anyone could point me in the direction of something I could have missed that would be a huge help thank you



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I think from your message you're talking about two different technologies - correct me if I'm wrong (I blame consumer marketing for this nonsense) - but you have an LED wall at the back - individual LED pixels on panels that form a wall; and four "LED" monitors - LCD TV's with LED backlights - mounted to the tracks?

On the "LED" monitors you'll pretty much always get this - the LED backlight will be on all the time, even when the screen is being sent a black image. There are some screens which will dynamically adjust the backlight brightness down to zero with a black screen, but it can take a while to find the correct combinations of options to do this.

On the other hand, with an LED wall, the only time I've ever seen this is either when an analogue signal is being sent to the screen and it's not set up right; and/or someone has been playing with the screen settings, boosting brightness/contrast settings and raising the black level so that black is actually displayed as a dark gray.

How are you actually distributing the video feeds? HDMI / SDI / Displayport / VGA / analogue video?

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I think the OP means the problem is that when he sends a 'black' screen down to the LED wall, the screen does still emit light insomuch as it's a dark grey 'look'. ie not as black as the screens would be if they were powered off. I've seen exactly this on the few occasions I've used LED panels, (also using Novastar) and yes it is a little tiresome when you need a full DBO but are left with a big ALMOST black square shape in the middle of the stage. 

The reference to the LED screens being black I suspect is him saying that he has the monitors set to black backgrounds etc to try to emulate sending that blackness through the processor/scaler in an attempt to send as black as he can, and not specifically part of his problem 🙂

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The LED wall controller will have a brightness setting. It may be worth experimenting with this, there is probably a balance to be struck where the black level is low enough but the actual material isn't too dim. 

One venue that I work in from time to time end up running their wall at 5% brightness after dark. 

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I could probably take an educated guess about which ship you’re on….

there will be a management/support contract in place with the suppliers to answer technical queries for that setup …. But you’re not the first team to ask that question and to date (because of the kit actually installed) outside of turning down the brightness significantly  or cutting the power completely, there’s not a way to make those specific screens properly “black”

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Thanks everyone for your replies! 

We're still tinkering today with the brightness and to answer the first post we're using SDI to HDMI converters for the LED screens, you're right they are essentially just 4 portrait TV's. The LED wall at the back is as you'd expect LED pixels on panels and that is direct SDI.

It's a tough one and I'll follow up on this thread if we manage to get the look we're after.


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I forgot to mention we were going through a Kramer K1 before the Vidtel. Now we've bypassed the Kramer and gone straight into the Sending/Receiving card we have a true blackout on the LED wall at the back when needed. 

Next we're going to have a look at the Greyscaling on the 4 Monitor screens on stage.


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