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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 8th Feb 2017, 3:34 pm   #1
Panrock
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Default Shutter rate on phone video camera

Recently I made my very first YouTube upload. It's a short clip, taken on my phone, that shows my 120-line colour mirror screw project in operation. See here. For those for whom a mirror screw is an unknown concept, I attach a view of the device at rest here.

There is absolutely no 'storage' on the mirror screw display so there is a travelling frame bar on the phone's picture. I wasn't able to stop it by tweaking the frame rate (~25Hz), so am I correct that the frame refresh rate on phone cameras is 30Hz - legacy from US originated standards perhaps? Or is the truth somewhat more complicated?

Steve
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Last edited by Panrock; 8th Feb 2017 at 3:42 pm. Reason: Sorry! this post is in the wrong section! Mods please move...
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Old 8th Feb 2017, 5:02 pm   #2
BassoonBloke
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Thumbs up Re: Shutter rate on phone video camera

Hi Steve,

Disregarding the moving frame bar, that is a very impressive show for a set of rotating mirrors !!
I'm really impressed. Can you do a few more videos of the system working please (I know you have some stuff on your website - but I want MORE !!).
Excellent stuff.

Cheers,
Alan.
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Old 8th Feb 2017, 5:06 pm   #3
Vauxfan2k
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Default Re: Shutter rate on phone video camera

I know for an iPhone for example the frame rate for 720p and 1080p standard is 30fps, for full HD you can change it to 60fps.

Depending on you make and model of phone your frame rate me be 30 max.

I know that my iPhone 6s at 60fps captures flickering vfd displays and slow refreshing LCD displays. 30fps does not and the display appears the same as the naked eye.

Not sure if this is what you're looking for info wise?

Steve
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Old 8th Feb 2017, 5:11 pm   #4
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Default Re: Shutter rate on phone video camera

Some cameras DSLR, (which do video very well) and video have a de-flicker mode, very useful.
 
Old 9th Feb 2017, 10:40 am   #5
peter_scott
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Default Re: Shutter rate on phone video camera

Hi Steve,

The Sony TRV22E Hi8 camcorder has a slow shutter selection that gives a 25th, 12th, 6th and a 3rd of a second.

I find it works quite well on 405 line recording off the screen. See:
https://www.youtube.com/watch?v=e7Q0wGfeMPo

Peter
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Old 9th Feb 2017, 11:17 am   #6
Panrock
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Default Re: Shutter rate on phone video camera

It does appear my Samsung phone camera is working at 30Hz and therein lies the problem.

Quote:
Originally Posted by BassoonBloke View Post
Disregarding the moving frame bar, that is a very impressive show for a set of rotating mirrors !!
Thank you. I'll go and post some 'quick facts' about this device over in the (more appropriate) Homebrew Equipment section.

Steve
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Old 9th Feb 2017, 8:16 pm   #7
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Default Re: Shutter rate on phone video camera

The shutter options of my first camcorder, a JVC GR M7 (VHS-C) included 1/50 and 1/60 sec. Using the 1/50 speed it would record from TV with no bar if you switched on and off enough times so that the camcorder and TV were in synch. I used it to record from SECAM French TV by filming from a TV screen. The 1/60 sec setting did not entirely eliminate the bar on 60Hz TV, but replaced it with a couple of narrow static bars that were much less objectionable. I only made us of this a couple of times, when videoing my children using a large screen amusement arcade game, and in an aircraft, where the on-board TVs were evidently using US NTSC. Subsequent consumer camcorders have progressively reduced the manual options.

I think that because current consumer video camera have such short focal length lenses, they have to operate at relatively large apertures (f/ numbers ) to avoid unsharpness due to diffraction, and because the sensors are so sensitive, they need to use very high shutter speeds. Hence the very juddery images that now seem to be found universally these days, even on broadcast TV. The manual of my GR M7 explicitly said that use in bright sunlight could result in loss of sharpness due to diffraction when using the 1/50 speed, and advised using a x4 neutral density filter to overcome this, which I always did. Nowadays manufacturers seem to have simply removed the 1/50 sec functionality from consumer video cameras that I always preferred for its smoother filming of moving objects.
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Old 9th Feb 2017, 9:18 pm   #8
dominicbeesley
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Default Re: Shutter rate on phone video camera

Hi Steve,

What's the frame rate of your screw? You could try turning the contrast right down and filming in a darkened room, this makes some phones slow their frame rate down, whether it will match any better is another matter. I keep meaning to write a video processing tool that will eliminate this effect on mechanical tv recordings, another thing on mile pile of round tuits...
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