Projection flicker

So I am planning a livestream from a church building, at the front are 3 projectors - one that fills the back wall as a kind of backdrop and then one either side of this that projects song words/powerpoint slides etc.


The back wall one and the projector on stage right are both fine in camera No flicker, no issues.
However, the one on stage left does have flicker unless the shutterspeed is 1/60 (I did consider running everything at 30fps but that cause some flickering issues with the lighting.)

I think what the issue is, is that only the stage right receives a signal directly from the computer and it then passes this on to the stage left. The side projectors are both the same make/model and are both using vga with longer distances over ethernet. Both projectors are set up with exactly the same settings.
I figured it could be some kind of latency issue, but it's not immediately clear that any of the settings fit this issue.


Camera wise, I am using 2x Pocket 4Ks at 25fps with a shutterspeed of 1/50 and the flicker free shutter set to 60hz. Recording into OBS at 25fps off an ATEM mini (set up at 1080p25.) The issue occurs in both cameras.
In terms of the setup - one camera is tight on the speaker whereas the second is a wider kind of establishing/safety shot.


Any suggestions?

Check the computer that drive projector, you can setup the refresh speed to 50 hrz, also cheap projectors like my home theatre projector optoma had 24, 50, 60 hrz that you can select from computer (Mac and windows).
Change all to 50 hrz to be compatible with shutter speed 180 degree.


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I had a look into that, but I only seemed to be able to set it to 60.

It's a windows machine and the windows setting only had 60hz and it was the same when I was using the AMD catalyst software (the machine is running an AMD GPU)

I had a look into that, but I only seemed to be able to set it to 60.

It's a windows machine and the windows setting only had 60hz and it was the same when I was using the AMD catalyst software (the machine is running an AMD GPU)

if you duplicate your monitor to projector it's forced to work 60hrz only, if you setup projector like second screen you can change frequency. check it.