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Capturing CRT TV screen

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Norbert Szabo
Capturing CRT TV screen
on Oct 16, 2017 at 5:08:57 am

Hi,

I am new to cameras and recording video and I need your help folks.

- I have an analog SD video signal (composite/s-video/component) (both 50Hz and 60Hz)
- There are few CRT TVs and monitors
- Budget - ~$2k for all the equipment (used/renting equipment could fine - would prefer buying)

My goal is to compare the visual quality of the image on the TVs and capture _high quality_ (1080p at least, 4k? maybe HDR) actual footage of the TV screens for demonstration purposes.

Capturing the signal directly is _not_ an option - because it is about the TVs display and not as much about the signal itself.

I believe I have an idea how to solve most problems (geometry, dynamic range, colors) - but the issue I am at loss is how to deal with syncing the recording rate with the video signal/tv refresh.

Since we are talking about high quality footage any banding/out of sync artifacts are out of question.

So, I did a bunch of research - could not find any obvious solution. I spent a lot of time reading it seems to me that I need a camera that does gen lock. I also read about "clear scan" or "synchro scan" - is that even an option on modern camcorders? How about LANC? Anyway, I am pretty confused as you can tell.

I have _no_ experience whatsoever using pro/semi pro equipment - but I am quick learner. Not attached to any particular brands - looking for a best bang for the buck option.

Thanks a bunch in advance!


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Mark Suszko
Re: Capturing CRT TV screen
on Oct 16, 2017 at 8:36:46 pm

Shooting analog TV CRT's, what you're looking for is a video camera with an adjustable (variable) shutter rate - Sony's name for that feature is "clear scan", but other camera makers also have it on mid-range and higher-end broadcast cameras. That's what gets the shutter to blink at the same rate as the electron beam sweeping across the CRT is "painting" the video line-by-line. You don't see this feature on many consumer-level camcorders, so, you may have to rent from a broadcast Video rental company. It's not much use on CRT's any more because CRT's are mostly extinct, except for a few niche applications - however, it remains useful to reduce flicker from some types of LED lighting.


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Norbert Szabo
Re: Capturing CRT TV screen
on Oct 17, 2017 at 5:32:07 am

Thanks a lot for your response - it would be super cool if I would be able to get away with not using genlock.

So "clear scan", please correct me if I am wrong - it is a way to fine-tune shutter speeds and frame rates, right?
That sounds super useful to tune it to 59.94Hz (NTSC) - I am wondering though if torn frames (or shearing) could be a problem when the video is panning? Do I want to synchronize when the screen starts painting and the camera starts the capturing? Otherwise I could end up with an issue that the updates rates match but the bottom "half" and the top "half" of the screens are from two different frames? I guess I could try the capture multiple times and _hope_ that I am lucky and I hit the vertical blank interval - but that sounds like a frustrating experience.

This is theoretical obviously so I could be totally wrong - please let me know! ☺

Anyway, I did some research and even "clear scan" sounds like a dying feature - could not found any cameras on Sony's site which do that.

Thanks again,
Norbert

ps: I found some Canon cameras which do have a genlock input - Canon XF105 and XF205 - none of them are 4k though. Can any of you good folks confirm that with a simple Y adapter I should be able to connect my video signal to both the genlock input and the CRT TV, press record and I am good?


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Mark Suszko
Re: Capturing CRT TV screen
on Oct 17, 2017 at 1:15:35 pm

Genlocking makes the cameras easy to cut between when using a switcher. it syncs the cameras to the same time base but does nothing about the CRT you're shooting. It's not going to help with your problem as stated. Variable "clear scan" shutter will synchronize each camera to the refresh rate of the CRT, you have to "dial it in", adjusting until the flicker and traveling line goes away. It's very much still around, on broadcast quality cameras, which you may not be able to afford to buy, but certainly can rent. Prosumer camcorders aren't going to cut it.


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Norbert Szabo
Re: Capturing CRT TV screen
on Oct 17, 2017 at 11:01:51 pm

All right - i guess this is the plan. I will do some more research into which particular camera I want and report back!

Thanks a lot once again!


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