Jump to content


Photo

Understanding D-Min for 16mm.


  • Please log in to reply
6 replies to this topic

#1 John Mackey

John Mackey
  • Basic Members
  • PipPip
  • 24 posts
  • Cinematographer

Posted 10 April 2012 - 10:37 AM

Just got some older color negative stock back from the lab. I had a 400 roll of Kodak Vision 500T, 320T and 250D tested. The results

500T: R=.42, G=.96, and B=1.37 ND=.65
320T: R=.38 G=.85, and B=1.28 ND=.60
250D: R=.50 G=.86, and B=1.12 ND=.69

What do these numbers mean? Should I overexpose? Underexpose?
  • 0

#2 Mark Dunn

Mark Dunn
  • Basic Members
  • PipPipPipPip
  • 2422 posts
  • Other
  • London

Posted 10 April 2012 - 01:17 PM

Just looking at the 500D, the last graph on this data sheet
http://motion.kodak....5263_ti2517.pdf
shows what the densities should be on fresh stock.
0.30 is 1 stop of density, your clip test has rather more than 1 stop more density than it should have, so you need to over-expose by rather more than 1 stop.
The difference in the red is about 0.2, green 0.4 and blue 0.4. The differences in density don't matter too much, they're dealt with in grading.
I'm sure you'll get some better advice soon.
  • 0

#3 Jay Stewart

Jay Stewart
  • Basic Members
  • PipPip
  • 50 posts
  • Industry Rep

Posted 10 April 2012 - 04:14 PM

typical RGB readings on any of those stocks should be 14-20 for R, 50-65 for G, 84-100 for B. Red is the outer layer and looks to be totally shot for those stocks you have, meaning they'll produce a variety of uncontrolled results from a faded, grainy, desaturated picture, to not rendering much of an image at all. If you're shooting something a little experimental, they try it, but that stock really belongs in the recycling bin to be quite honest.
  • 0

#4 John Mackey

John Mackey
  • Basic Members
  • PipPip
  • 24 posts
  • Cinematographer

Posted 10 April 2012 - 05:31 PM

typical RGB readings on any of those stocks should be 14-20 for R, 50-65 for G, 84-100 for B. Red is the outer layer and looks to be totally shot for those stocks you have, meaning they'll produce a variety of uncontrolled results from a faded, grainy, desaturated picture, to not rendering much of an image at all. If you're shooting something a little experimental, they try it, but that stock really belongs in the recycling bin to be quite honest.


I will be converting the footage to black and white in post production. So does the RGB really matter?
  • 0

#5 Charles MacDonald

Charles MacDonald
  • Sustaining Members
  • 1157 posts
  • Other
  • Stittsville Ontario Canada

Posted 10 April 2012 - 06:15 PM

I will be converting the footage to black and white in post production. So does the RGB really matter?

to make B&W you combine all three colours, so if the stock is has gone grainy you will get extra grain. if the colour ballance is too far off it will look like you used a random B&W filter. OTOH, any colour shift will not matter in B&W.
  • 0

#6 John Mackey

John Mackey
  • Basic Members
  • PipPip
  • 24 posts
  • Cinematographer

Posted 10 April 2012 - 08:40 PM

to make B&W you combine all three colours, so if the stock is has gone grainy you will get extra grain. if the colour ballance is too far off it will look like you used a random B&W filter. OTOH, any colour shift will not matter in B&W.


The lab said I should overexpose, but since I am shooting mostly night ext and int, and I have a lens that only goes f 2.2, would adding more light be effective?
  • 0

#7 Charles MacDonald

Charles MacDonald
  • Sustaining Members
  • 1157 posts
  • Other
  • Stittsville Ontario Canada

Posted 10 April 2012 - 09:07 PM

Adding more light, or opening the lens wider or the two ways that one can add exposure. (slower frame rate is another as it leaves the shutter open longer but of course that speeds up the action.)
  • 0


Visual Products

Technodolly

CineLab

Abel Cine

Willys Widgets

Broadcast Solutions Inc

CineTape

Rig Wheels Passport

rebotnix Technologies

Media Blackout - Custom Cables and AKS

Opal

Tai Audio

Wooden Camera

The Slider

Metropolis Post

FJS International, LLC

Glidecam

Aerial Filmworks

Gamma Ray Digital Inc

Paralinx LLC

Ritter Battery

Gamma Ray Digital Inc

Media Blackout - Custom Cables and AKS

The Slider

Willys Widgets

Paralinx LLC

rebotnix Technologies

Aerial Filmworks

Abel Cine

Technodolly

Visual Products

Metropolis Post

Ritter Battery

CineLab

Tai Audio

FJS International, LLC

Rig Wheels Passport

CineTape

Wooden Camera

Glidecam

Broadcast Solutions Inc

Opal