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  1. Member
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    Hello everybody! In about a week I am going to be doing videography at an event in Europe. I will be filming with NTSC cameras at 1080p60fps (Canon XA25's, not that it matters). I am not worried about flicker from the lights, as I am matching with the shutter speed at 1/100. However, I have just learned that there is going to be a projector screen display on the stage of the event, and will definitely be seen in the background of my footage. I am operating under the assumption that this will be a front projection screen in PAL, most likely 25fps, but it might be 50.

    How concerned should I be about this screen looking funky on my cameras? Obviously I would prefer to have it look normal with no flicker or strobing, so I am trying to get a better understanding of this situation before I am already overseas at the venue. Is it safe to keep the cameras at 1/100 and the screen should behave like the lights? Or is this likely to cause problems with the appearance of the screen on video? I can't seem to find any specific information online pertaining to cross-region shooting with a projector screen involved, everything I can find is only concerned with light sources. Hoping this will be less of a headache than I expect it will be...

    Thanks for reading!
    Last edited by setagneb; 2nd Aug 2017 at 11:44.
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  2. Member
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    You will have trouble with a scanning CRT projector. But how likely is that? Most projectors these days are digital progressive machines.
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  3. Explorer Case's Avatar
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    The movie for the projection will have a certain frame rate, but the projector may have a refresh rate that is much more (200/240 Hz), probably a multiple of the utility frequency as well. It is also different for LCD projectors and DLP projectors, so it all depends on a bunch of unknowns.

    If it all fails, there's a software solution to remove flicker. Better to prevent it, but it might save your ass. https://www.digitalanarchy.com/Flicker/main.html
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  4. Member Cornucopia's Avatar
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    Not just flicker to worry about but redraw sync issues. Even assuming steady & accurate clocks running at unison/multiple framerates in both proj and cam, if they don't start frame at same time you will either have blended frames, screen "tearing", "hum bars" or stuttering, or some combination.
    Example: running 50fps on both proj & cam with cam's sh speed = 1/100th sec (aka 1/2 frame dwell time aka 180degree shutter). If they start and cam is 1/200th sec delayed compared to proj...

    That is why pro organizations use a master sync source with genlocked cams AND projectors in high end productions.

    Scott
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  5. Member
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    Thanks for the replies folks. I am trying to get information from the venue about precisely the make and model number of the projector.

    I am wondering if anyone could shed some light on a theoretical combination of refresh rate and frame rates which would be most likely to work seamlessly with 60fps at 1/100? Or if there is some math that could be used to find a conclusion? I would like to walk into this situation with a rough idea of a configuration which might work.


    If it all fails, there's a software solution to remove flicker. Better to prevent it, but it might save your ass. https://www.digitalanarchy.com/Flicker/main.html
    It's good to know this could be an option, but the work I am doing is going into an extremely time-sensitive workflow and really would not allow for the added time it will take to apply and tweak this plugin, not to mention it will likely take much longer to export (I am going to be processing a lot of videos and they need to be prepared in a very short amount of time). But, I might have some time at the venue to experiment, perhaps it will be useful if I can figure out the settings in advance, so thanks.

    That is why pro organizations use a master sync source with genlocked cams AND projectors in high end productions.
    Lol yeah, well unfortunately, I am the only person in my particular industry who can provide any semblance of high-end production within the budgetary limits of this event.
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  6. Member
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    So get there early for the rehearsal and try different settings on your camera until the projection looks decent.
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  7. Member
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    Conclusion:

    The screen was not a problem at all at 1/100, so I am assuming it was 50hz.
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