Jump to content


Photo

increase/decrease stops


  • Please log in to reply
3 replies to this topic

#1 Jon Bel

Jon Bel
  • Basic Members
  • PipPip
  • 25 posts
  • Director

Posted 09 October 2010 - 08:31 AM

I'm currently reading Kodak's reference guide for filmmakers. I'm looking over the chart for conversion filters and I will be using the 85 filter to do some tests. It says that the exposure increase in stops is 2/3. I know what it's saying but just wanted to be sure. Does increase means close down or open up on lens or does it simplify things to just change exposure index on meter?

My meter is set at 320EI currently. My shutter angle is 120deg (older camera). My filter will be amber 85.
My manual says shutter at 120 - decrease 2/3 stops. Taking all this into consideration, how should I expose this?

I need cinematographer knowledge.
  • 0

#2 Kyle Reid

Kyle Reid
  • Basic Members
  • PipPip
  • 23 posts
  • Industry Rep
  • Baton Rouge, LA

Posted 09 October 2010 - 11:10 AM

I'm currently reading Kodak's reference guide for filmmakers. I'm looking over the chart for conversion filters and I will be using the 85 filter to do some tests. It says that the exposure increase in stops is 2/3. I know what it's saying but just wanted to be sure. Does increase means close down or open up on lens or does it simplify things to just change exposure index on meter?

My meter is set at 320EI currently. My shutter angle is 120deg (older camera). My filter will be amber 85.
My manual says shutter at 120 - decrease 2/3 stops. Taking all this into consideration, how should I expose this?

I need cinematographer knowledge.


It means that in order to compensate for the light lost (absorbed) by the 85 filter, that you need to open up the aperture to allow more light in. The amount of compensation needed is 2/3s of a stop, so to correctly compensate, open the aperture 2/3s of a stop. You can account for this change by setting your meter to a lower effective film speed. Since you are set at 320 film speed now, you can set your meter from 320 down to 200 film speed. This way you can meter, and correctly compensate for your light loss.
  • 0

#3 Jon Bel

Jon Bel
  • Basic Members
  • PipPip
  • 25 posts
  • Director

Posted 09 October 2010 - 04:45 PM

Thanks Kyle, just wanted to confirm this.



It means that in order to compensate for the light lost (absorbed) by the 85 filter, that you need to open up the aperture to allow more light in. The amount of compensation needed is 2/3s of a stop, so to correctly compensate, open the aperture 2/3s of a stop. You can account for this change by setting your meter to a lower effective film speed. Since you are set at 320 film speed now, you can set your meter from 320 down to 200 film speed. This way you can meter, and correctly compensate for your light loss.


  • 0

#4 Bill DiPietra

Bill DiPietra
  • Sustaining Members
  • 2339 posts
  • Cinematographer
  • New York City

Posted 09 October 2010 - 06:22 PM

In my experience, the manufacturer's recommended filter factor is very often a rather conservative one. You will probably find that you will need a full stop to compensate for the filter. If this is just a test roll, I would shoot at some different exposures and keep a record of each shot. This way, when you get the film back from the lab, you can see what worked and what didn't.
  • 0


Technodolly

Glidecam

Media Blackout - Custom Cables and AKS

Broadcast Solutions Inc

FJS International, LLC

Gamma Ray Digital Inc

Metropolis Post

New Pro Video - New and Used Equipment

Ritter Battery

Aerial Filmworks

Tai Audio

CineLab

CineTape

Visual Products

Willys Widgets

The Slider

rebotnix Technologies

Rig Wheels Passport

Wooden Camera

Abel Cine

Paralinx LLC

Technodolly

Media Blackout - Custom Cables and AKS

Gamma Ray Digital Inc

Wooden Camera

New Pro Video - New and Used Equipment

rebotnix Technologies

Paralinx LLC

Metropolis Post

Glidecam

Abel Cine

FJS International, LLC

Tai Audio

Broadcast Solutions Inc

Ritter Battery

Willys Widgets

Aerial Filmworks

CineTape

Visual Products

Rig Wheels Passport

CineLab

The Slider