Filming LED Screens and dot pitch Moiré

[David Baumber]

We have a large 7mx3m LED screen with pixel density at 3.9mm being installed as a backdrop to one of our scene. Imagine advertisements in Blade Runner on large buildings.... well this is our small version.

Has anyone filmed with 3.9mm LED and do you think it will cause serious moiré issues. We may need to test but advice would be very welcome. The screens can be slightly out of focus to combat the moiré or are there other tricks we could use?

Thanks for any help.

David

 

[Ulf Krentz]

This will also pretty much depend a the distance of the screen (size in the picture) and even when OK in full resolution may end up in trouble when downscaling. One other thing will be the refresh rate of the image which might cause flicker or strobing. Do various tests prior to shoot.

 

[Todd T]

One thing to try; lighting up the screen as a solid green (or blue) and key the image into a tracking matte in post, just in case the direct image tests don't work out.

 

[Elsie N]

Probably want to turn down the brightness to keep the screen from dominating the shot.

On another note, I've shot a screen directly before and the RED has such resolution that the screen matrix showed through.

 

[Nathan Grubbs]

Probably want to turn down the brightness to keep the screen from dominating the shot.

On another note, I've shot a screen directly before and the RED has such resolution that the screen matrix showed through.

+1 on the brightness thing. I've shot a ton with LED walls and it is very easy for the screen to overtake your image. Even on the lowest LED wall brightness setting it can be too bright depending on the content. Working on developing balanced content for the screen is key here.

oh and moire is pretty much impossible to avoid to some degree. It all depends on your distance from the screen. Shallow DOF helps a little.

 

[David Baumber]

Thanks All, That's really helpful advice.

 

[Phil Holland]

You will definitely need to test it first as some LED screen tech I've seen used for wall type imaging also have off phase refresh rates and occasionally row or column dependent. You might be filming 10 columns that uniquely phase with themselves and then the 11-20 and so on will be on the same cycle left to right.

Just depends on the tech. 1/60th is a safe bet if you are stateside.

 

[Björn Benckert]

We shot some big led screens back in epix mx days... the result was terrible. The screen was about 10x4 meters and we where filming it full frame... This was early epic no playback in camera etc. and we did not have too much dit skills at the time so later in post we sa that the image was not usable at all. So do tests before you shoot it for real. We thought that having it slightly out of focus would help... well not so much it made the colors go nuts and when camera moves the color change etc.

The phase shift phil mention is not much of a problem on the bigger screens they can do 25hz, 50hz, 24hz etc.

do tests and render to final delivery resolution and make sure to test with the focal lenght, distance to screen frame rate, camera move and f stop you intend to use... Simply put i think you will find out that if focus is on the foreground then big led screens are far from optimal as backgrounds.

 

[Peter John]

Also to keep in mind, playback content, visuals will too have an effect depending on the computer signal or device pushing the content to the screens, also there brightness and opacity fading in and out will cause more or less moire/banding at lower intenisty.
And different focal lengths on lenses also render the led image differently. Foreground image in focus and led screen out of focus on a 24mm lens can really bring up some nasty banding.

I have spent the last 4 years filming large multi camera concerts on reds and large array of massive LED screens and moving lights , lasers and led movers. Spent way too long getting these things to work, but it seems there is never one solution, there are way to many variables.
Happy to help anyone on the forum get the best result

One of my reels with examples:

https://www.youtube.com/watch?v=gBNnOPLGwtI