Filming LCD screen correctly.

[Jannik Tesch]

Good day,

I get this "ghosting" when there is movement on the MacBook's screen. In this case it is vertical scrolling.

It's a 2012 MacBook Pro, but the same effect appears on my much newer iPhone XR, so I guess the problem is screen independend. I'm in Europe.

I tried shooting @24fps with all available shutter angles the camera has to offer. I'm on a Blackmagic Pocket Cinema Camera 4K.

I also tried 25, 30, 60 fps @ 172.8° – no solution.

 

What am I doing wrong?

Thanks in advance

Jannik

[Jannik Tesch]

Also tested in different Apps, YouTube videos and a 2017 MacBook Pro. All the same issue. It looks like frame interpolation.

[Andy Jarosz]

You’re not doing anything wrong, the refresh of the screen simply isn’t synchronized to the camera shutter. Even if they’re running at the same frame rate, if the phase is offset, you will get double frames.

 

if you can’t sync the screen and camera via genlock, there’s nothing you’ll be able to do.

[Jannik Tesch]

Thanks, Andy, that is helpful information.

From that I derive that for properly filming screens, you need to genlock sync them with the camera, no matter what? So every MacBook and iPhone you see in films / television (which is a lot these days) is synced to the camera via genlock?

How do you do that, if I may ask? (Haven't research that myself, yet)

[Andy Jarosz]

Most of the time screens are replaced with VFX.

Im not sure if it’s possible to genlock a macbook, it’s definitely not possible for a phone.

[Albion Hockney]

most of the time its a vfx comp

[Jannik Tesch]

I see, thank you!

[Robin Phillips]

What is the refresh rate of that monitor? if its 30hz (or even under 60hz potentially) you may encounter problems. If you have another laptop that can do 120hz or higher, you're unlikely to see this sort of behavior (you dont see it at all on TVs anymore). I would test this with a 180 degree shutter if you have not already. I see you're in europe, so I'd see if you can manually jam the laptop display to 50hz or 100hz while shooting at 25fps and see if that improves things. 

I'd note I have shot iphone screens at 24fps and a 180 degree shutter on an alexa before and we were able to use the in camera footage without manipulation, and there was no ghosting. so I wonder if the 180 degree shutter is necessary.

If you have to use THIS laptop, try plugging the laptop and the camera into the same wall circuit. IF the laptop will actually directly pull power from the wall (without going thru the battery first), then it may phase jam the two devices to eachother and get you what you need. If theres anything else messing with how power is delivered to the display though this may not work. 

In that case, I'd use some screen capturing software to record whats happening on the screen separately, and then do a screen replacement (odds are you can track the display corners alone and not need tracking markers. If you do the take with a dark screen (which will keep your reflections), and then you record the screen and motions matching what you wanted in the good take, you should be able to comp it in relatively easily. 

Your last option would be to get a phase sync box like the one cinematography electronics made, but to be honest I've never used one with a digital camera so I've got no idea if it would play ball or not.

good luck

[Phil Rhodes]

18 hours ago, Andy Jarosz said:

You’re not doing anything wrong, the refresh of the screen simply isn’t synchronized to the camera shutter. Even if they’re running at the same frame rate, if the phase is offset, you will get double frames.

 

if you can’t sync the screen and camera via genlock, there’s nothing you’ll be able to do.

What he said.

[Jannik Tesch]

Thanks for your detailed answer.

15 hours ago, Robin Phillips said:

try plugging the laptop and the camera into the same wall circuit. IF the laptop will actually directly pull power from the wall (without going thru the battery first), then it may phase jam the two devices to eachother and get you what you need.

Tried that, but didn't solve the problem.

I might just live with it.