Jump to content


Photo

ND4 filter question


  • Please log in to reply
4 replies to this topic

#1 Patrick Barry

Patrick Barry
  • Basic Members
  • PipPip
  • 37 posts
  • Director
  • Jacksonville, FL

Posted 12 March 2010 - 12:23 PM

Ok, so here goes a pretty dumb sounding question that I will ask anyway. If I pop an ND4 filter onto my lens, and the exposure would normally be an 11, do I count that stop (the 11) as one of the 4 stops down? If that makes sense?

Would it be a 4 or a 2.8.

Thanks guys!!
  • 0

#2 Brian Drysdale

Brian Drysdale
  • Basic Members
  • PipPipPipPip
  • 5070 posts
  • Cinematographer

Posted 12 March 2010 - 12:52 PM

It actually reduces by 2 stops, the 4 refers to a 1/4, so at f11 you'd open to f5.6 with the filter on.

This explains the method used for defining ND filters.

http://www.cs.mtu.ed.../filter-ND.html
  • 0

#3 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19759 posts
  • Cinematographer
  • Los Angeles

Posted 12 March 2010 - 12:52 PM

Ok, so here goes a pretty dumb sounding question that I will ask anyway. If I pop an ND4 filter onto my lens, and the exposure would normally be an 11, do I count that stop (the 11) as one of the 4 stops down? If that makes sense?

Would it be a 4 or a 2.8.

Thanks guys!!


I don't know why, but the still camera filter market is now using "ND4" to mean a 2-stop ND and "ND8" to mean a 3-stop ND -- I guess because a filter factor of 4 is 2-stops and a filter factor of 8 is 3-stops.

In cine terms, a 2-stop ND would be an ND.60 and a 3-stop ND would be an ND.90.

So an ND4 filter would mean you'd have to open from f/11 to f/5.6 to compensate.
  • 0

#4 Eric H

Eric H
  • Basic Members
  • PipPip
  • 29 posts
  • Cinematographer
  • New York

Posted 12 March 2010 - 01:00 PM

I don't know why, but the still camera filter market is now using "ND4" to mean a 2-stop ND and "ND8" to mean a 3-stop ND -- I guess because a filter factor of 4 is 2-stops and a filter factor of 8 is 3-stops.

In cine terms, a 2-stop ND would be an ND.60 and a 3-stop ND would be an ND.90.

So an ND4 filter would mean you'd have to open from f/11 to f/5.6 to compensate.


someone, somewhere is going to get a nasty surprise one morning in telecine......my suggestion to anyone who's not sure, is to run your spot meter thru anything that might require compensation...if you don't have a spot meter then use your still camera and watch the number of stop loss the meter says when you put your filter in front. If you use the camera method be sure to use a uniformly lit object, like the sky or the white cyc/limbo in a studio, or a grey card.

good luck,
Eric
  • 0

#5 Patrick Barry

Patrick Barry
  • Basic Members
  • PipPip
  • 37 posts
  • Director
  • Jacksonville, FL

Posted 22 March 2010 - 08:20 PM

Thanks all! That certainly explains a lot! :)
  • 0


CineTape

rebotnix Technologies

Glidecam

Wooden Camera

CineLab

Gamma Ray Digital Inc

Visual Products

Ritter Battery

Willys Widgets

Opal

Abel Cine

Paralinx LLC

The Slider

Media Blackout - Custom Cables and AKS

Metropolis Post

FJS International, LLC

Broadcast Solutions Inc

Rig Wheels Passport

Aerial Filmworks

Technodolly

Tai Audio

Media Blackout - Custom Cables and AKS

Tai Audio

CineTape

Aerial Filmworks

Gamma Ray Digital Inc

Technodolly

Ritter Battery

rebotnix Technologies

Broadcast Solutions Inc

Paralinx LLC

Metropolis Post

Abel Cine

FJS International, LLC

CineLab

Visual Products

Rig Wheels Passport

Wooden Camera

The Slider

Willys Widgets

Opal

Glidecam