Jump to content


Photo

proper shutterspeed for shooting a T.V. screen?


  • Please log in to reply
10 replies to this topic

#1 tym

tym

    New

  • Basic Members
  • Pip
  • 1 posts
  • Student

Posted 11 November 2005 - 06:47 PM

I am shooting a student film tomorrow with a Panasonic DVX 100, and was wondering if there was a proper shutter speed for shooting a Television without getting the black bars. Perhaps there is another way to shoot a T.V. without relying on fixing it in post?

thanks

tim
  • 0

#2 Preston Herrick

Preston Herrick
  • Basic Members
  • PipPip
  • 89 posts
  • Producer
  • Washington

Posted 11 November 2005 - 06:52 PM

1/60th
  • 0

#3 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19764 posts
  • Cinematographer
  • Los Angeles

Posted 11 November 2005 - 06:58 PM

You're assuming that he's posting from an NTSC country...
  • 0

#4 Robert Glenn

Robert Glenn
  • Basic Members
  • PipPipPip
  • 247 posts
  • Other

Posted 11 November 2005 - 07:40 PM

You're assuming that he's posting from an NTSC country...

How does 180deg shutter angle look when shooting NTSC at 24fps crystal?
  • 0

#5 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19764 posts
  • Cinematographer
  • Los Angeles

Posted 11 November 2005 - 09:19 PM

How does 180deg shutter angle look when shooting NTSC at 24fps crystal?


You get a big roll bar unless shooting an LCD screen.

At 30 fps, a 180 degree shutter gets you 1/60th of a second per frame.

At 24 fps, a 180 degree shutter gets you 1/48th of a second per frame.

At 24 fps, a 144 degree shutter gets you 1/60th of a second per frame.

So you want to be able to set your shutter to 144 degrees to reduce the SIZE of the roll bar from a thick band to a thin line. Then you want to run the camera at 23.976 fps instead of 24 fps. This will stop the thin line from rolling. A film-video sync box or a phase button on the camera will allow you to move the thin line to where it is least objectionable.

However, at 23.976 fps, you can't completely remove the line -- your choices are either to set it in the center of the TV screen, or have two lines, one at the top third and one at the bottom third of the screen. If you look at "The Abyss", the monitors on the ship at sea all have a line across the middle of the screen.

The only way to remove the line completely is to: (1) shoot at 29.97 fps (NTSC) -- negating doing a dialogue scene, but then you can use a 180 degree shutter, or (2) use a 23.976 fps monitor & playback deck (which also allows you to use a 180 degree shutter); or (3) use an LCD screen.

I'm talking about a film camera of course. The NTSC DVX100B at 24P mode actually shoots at 23.976P since it ends up getting a 3:2 pulldown added to get up to 59.94i (NTSC). So setting the shutter speed to 1/60th should be enough for shooting a TV; you can also shoot in "clear scan" shutter mode and set it to the correct hertz I believe (which is still close to 60 hz or 1/60th shutter speed.) Not sure how that appears in the menu system. You may find that the shot has to be a lock-off.

Edited by David Mullen, 11 November 2005 - 09:25 PM.

  • 0

#6 Preston Herrick

Preston Herrick
  • Basic Members
  • PipPip
  • 89 posts
  • Producer
  • Washington

Posted 12 November 2005 - 01:56 AM

You're assuming that he's posting from an NTSC country...


Yes, I was. I believe 1/60th is the default shutter speed on the DVX in NTSC land and 1/50th on PAL cameras - which would be correct for shooting TV's in PAL land (regardless of the frame rate you're shooting in). Pressing the shutter speed button will reveal it's current setting. The clear scan feature tends to be more useful when shooting computer CRT monitors with their highly varying refresh rates. Even with the shutter speed dialed in correctly, you may experience "tearing" or a fine bright scan line on the TV with any camera movement.

Edited by PrestonHerrick, 12 November 2005 - 02:01 AM.

  • 0

#7 Robert Glenn

Robert Glenn
  • Basic Members
  • PipPipPip
  • 247 posts
  • Other

Posted 12 November 2005 - 11:30 AM

You get a big roll bar unless shooting an LCD screen.

At 30 fps, a 180 degree shutter gets you 1/60th of a second per frame.

At 24 fps, a 180 degree shutter gets you 1/48th of a second per frame.

At 24 fps, a 144 degree shutter gets you 1/60th of a second per frame.

So you want to be able to set your shutter to 144 degrees to reduce the SIZE of the roll bar from a thick band to a thin line. Then you want to run the camera at 23.976 fps instead of 24 fps. This will stop the thin line from rolling. A film-video sync box or a phase button on the camera will allow you to move the thin line to where it is least objectionable.

However, at 23.976 fps, you can't completely remove the line -- your choices are either to set it in the center of the TV screen, or have two lines, one at the top third and one at the bottom third of the screen. If you look at "The Abyss", the monitors on the ship at sea all have a line across the middle of the screen.

The only way to remove the line completely is to: (1) shoot at 29.97 fps (NTSC) -- negating doing a dialogue scene, but then you can use a 180 degree shutter, or (2) use a 23.976 fps monitor & playback deck (which also allows you to use a 180 degree shutter); or (3) use an LCD screen.

I'm talking about a film camera of course. The NTSC DVX100B at 24P mode actually shoots at 23.976P since it ends up getting a 3:2 pulldown added to get up to 59.94i (NTSC). So setting the shutter speed to 1/60th should be enough for shooting a TV; you can also shoot in "clear scan" shutter mode and set it to the correct hertz I believe (which is still close to 60 hz or 1/60th shutter speed.) Not sure how that appears in the menu system. You may find that the shot has to be a lock-off.

David many thanks (again)!
I'm stuck with a crystal 24 since my old beala motor's governed for a 60hz pulse. So you said a 23.976 monitor.. Are there not TVs or a tv system that can make a tv run at exactly 24 frames/48 fields per second for 24 frame camera shooting instead of 29.976/23.976? I think i'll have to live with a roll bar

Edited by RobertNC, 12 November 2005 - 11:30 AM.

  • 0

#8 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19764 posts
  • Cinematographer
  • Los Angeles

Posted 12 November 2005 - 11:37 AM

David many thanks (again)!
I'm stuck with a crystal 24 since my old beala motor's governed for a 60hz pulse. So you said a 23.976 monitor.. Are there not TVs or a tv system that can make a tv run at exactly 24 frames/48 fields per second for 24 frame camera shooting instead of 29.976/23.976? I think i'll have to live with a roll bar


Blame NTSC, which is 59.94 fields per second / 29.97 frames per second. So special 24 fps monitors and playback equipment actually run at 23.976 fps.

Now if your camera can run 25 fps crystal, a PAL monitor would run exactly at 25 fps.

If you can at least set your shutter to 144 degrees, running at 24 fps, you'd get a thin rolling line which is not too distracting in wider shots.

These days, you can save yourself a lot of trouble and just use LCD screens on the set.
  • 0

#9 Robert Glenn

Robert Glenn
  • Basic Members
  • PipPipPip
  • 247 posts
  • Other

Posted 12 November 2005 - 12:07 PM

Blame NTSC, which is 59.94 fields per second / 29.97 frames per second. So special 24 fps monitors and playback equipment actually run at 23.976 fps.

Now if your camera can run 25 fps crystal, a PAL monitor would run exactly at 25 fps.

If you can at least set your shutter to 144 degrees, running at 24 fps, you'd get a thin rolling line which is not too distracting in wider shots.

These days, you can save yourself a lot of trouble and just use LCD screens on the set.

Yeah I guess LCD will be the way to go. It just sortof doesn't feel like it fits in the context of my story, but I guess I can try gutting an old TV out to lend to the effect that I want if I'm bothered enough.
Does the LCD have any lighting/exposure issues worth mentioning?
  • 0

#10 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19764 posts
  • Cinematographer
  • Los Angeles

Posted 12 November 2005 - 01:06 PM

Does the LCD have any lighting/exposure issues worth mentioning?


Not really, other than many need to be shot close to straight-on or else they get darker. They are close to daylight-balanced just like CRT's. I've had LCD screens installed into prop computer CRT monitors for shooting computer scenes were a flatscreen was not justified by the character.
  • 0

#11 David Silverstein

David Silverstein
  • Basic Members
  • PipPip
  • 96 posts
  • Student
  • New York City

Posted 13 November 2005 - 05:06 PM

What you could do if you have a good set designer is get an lcd screen and build it into an older tv set box. Allowing the simplicity of the lcd screen with the look of an older tv :D. It shouldn't be to hard either if you need it that bad then its worth doing it.

Dave.
  • 0


Visual Products

Rig Wheels Passport

rebotnix Technologies

Abel Cine

FJS International, LLC

Media Blackout - Custom Cables and AKS

Glidecam

Ritter Battery

Tai Audio

Technodolly

Metropolis Post

Broadcast Solutions Inc

Willys Widgets

CineTape

Wooden Camera

CineLab

Gamma Ray Digital Inc

Opal

Paralinx LLC

The Slider

Aerial Filmworks

Paralinx LLC

Aerial Filmworks

Gamma Ray Digital Inc

Glidecam

Wooden Camera

CineTape

Media Blackout - Custom Cables and AKS

Willys Widgets

Rig Wheels Passport

Opal

FJS International, LLC

CineLab

Abel Cine

Technodolly

rebotnix Technologies

The Slider

Tai Audio

Visual Products

Metropolis Post

Ritter Battery

Broadcast Solutions Inc