Jump to content


Photo

push a stop and DI why?


  • Please log in to reply
8 replies to this topic

#1 Delorme Jean-Marie

Delorme Jean-Marie
  • Basic Members
  • PipPipPipPip
  • 513 posts
  • Cinematographer
  • paris, france

Posted 12 October 2008 - 10:34 AM

Hi all

i just red the artical about E. Lubezki on the Cohen brother movie.
he is explaining he he rating his 5229 stock at 400 asa wich is slightly overexposing.
It's something DP usualy do to add density on the positive when bringing the printing lights back.

but when you'r grading in DI what's the point theorically and in real life.

thx for your imputs i'm curious
  • 0

#2 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19761 posts
  • Cinematographer
  • Los Angeles

Posted 12 October 2008 - 11:17 AM

Hi all

i just red the artical about E. Lubezki on the Cohen brother movie.
he is explaining he he rating his 5229 stock at 400 asa wich is slightly overexposing.
It's something DP usualy do to add density on the positive when bringing the printing lights back.

but when you'r grading in DI what's the point theorically and in real life.

thx for your imputs i'm curious


Reason #1: more density means less graininess since you are exposing more of the smaller, slower grains (and 5229 is a somewhat grainy stock)

Reason #2: overexposing by 1/3 of a stop is hardly overexposing -- it's within a margin of error in exposing, so it's more of a safety net against occasional underexposing

Reason #3: anything you do to make a better contact print when shooting will probably translate well into a D.I. as well
  • 0

#3 K Borowski

K Borowski
  • Basic Members
  • PipPipPipPip
  • 3905 posts
  • Camera Operator
  • I.A.T.S.E. Local # 600 Eastern Region

Posted 12 October 2008 - 11:26 AM

Reason #2: overexposing by 1/3 of a stop is hardly overexposing -- it's within a margin of error in exposing, so it's more of a safety net against occasional underexposing


I don't remember OTOH Lubezki's shooting style with his non-DI films (although they're all very beautifully done; "A Little Princess" is a guilty pleasure of mine). However, he probably is overexposing far less than he normally would. 1/2-1 full stop of overexposure is commonplace with cinematographers.

Reason why you generally don't want to hit the negative with that much light with a DI is that scanners don't like overexposure (slows down scan times and highlights block up), whereas optical printers do like it.
  • 0

#4 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19761 posts
  • Cinematographer
  • Los Angeles

Posted 12 October 2008 - 11:30 AM

Others have different experiences, but after doing a few D.I.'s, most of the problems have been with underexposed footage more than anything else, and well or slightly overexposed footage color-corrects quite nicely, so the old rule that negative film likes exposure hasn't really changed.
  • 0

#5 Delorme Jean-Marie

Delorme Jean-Marie
  • Basic Members
  • PipPipPipPip
  • 513 posts
  • Cinematographer
  • paris, france

Posted 12 October 2008 - 11:32 AM

hello mr mullen
i can understand reason 2 and 3 but there won't be more density on the neg unless if you scan the print.
did i misunderstood something?

interesting point mr Borowski.
  • 0

#6 K Borowski

K Borowski
  • Basic Members
  • PipPipPipPip
  • 3905 posts
  • Camera Operator
  • I.A.T.S.E. Local # 600 Eastern Region

Posted 12 October 2008 - 11:43 AM

Absolutely agree with you David. You certainly never want to underexpose. "Gain boosts" to underexposed footage still stick out like a sore thumb.

Mind you now that I have only worked with 16mm, and my access to scanner/telecine equipment is certainly different than your access, but, with lower budget scanners, when the negative is too dense, a lot of times the scanner has trouble actually reading through it and it blocks up.

It doesn't get grainy like with underexposure, but you loose detail. You don't want to get, as the lab here calls it, "bulletproof" negatives when they are intended for scanning.
  • 0

#7 K Borowski

K Borowski
  • Basic Members
  • PipPipPipPip
  • 3905 posts
  • Camera Operator
  • I.A.T.S.E. Local # 600 Eastern Region

Posted 12 October 2008 - 11:48 AM

i can understand reason 2 and 3 but there won't be more density on the neg unless if you scan the print.
did i misunderstood something?


Delorme:

Density on the negative is also variable, just like a print, but the opposite.

When you OVEREXPOSE a negative, it gets denser.

When you UNDEREXPOSE, the negative is thinner.

So, by overexposing, you are basically using the slower, finer grains in the emulsion, as film has both slower smaller and faster bigger grains embedded. This has the effect of reducing the appearance of grain.

This is akin to what used to be done in the audio industry with "recording in the red". You wanted to saturate the tape with the recording so that the recording was so loud it drowned out the inherent tape hiss.

Overexposing film similarly gives enough exposure to hide the larger, faster grains in the film, by exposing more of the slower grains than if you were exposing at box speed.


Have we answered your question?
  • 0

#8 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 19761 posts
  • Cinematographer
  • Los Angeles

Posted 12 October 2008 - 12:21 PM

The reasons a denser negative make a better contact print is that:

#1 You get less visible graininess because you've exposed the smaller grains inbetween the faster larger ones
#2 You get better blacks from printing down, and thus better color saturation and more contrast ("snap").

Now when doing a D.I., you still get the benefits of #1, but black level in a digital realm is really a matter of how you set the color-correction, so you can make the blacks perfectly black ("0" let's say, or whatever the digital system considers pure black) even with grossly underexposed footage. Same goes for contrast and chroma levels, these can be set digitally. So there is less reason to overexpose negative for #2 if you are doing a D.I.

However, taking slightly overexposed images, even in digital color-correction, and bringing them down to normal still seems to work nicely for getting good blacks and a clean image because you have more shadow information to work with and then "bury" to some degree by pushing the blacks down, especially compared to working with slightly underexposed information.

Now you could say "just expose perfectly and it should work fine" but who exposes perfectly? You're almost always hovering within a 1/3-stop area of correction up or down even if you exposed at the normal rating and were very good (and didn't change your mind in post about how the scene should look - which of course never happens, you always have new thoughts about the look of the scene).

Which brings up another point, is that it is not unusual for studios, directors, producers, to end up wanting to brighten a scene compared to how the cinematographer shot them -- we cinematographers just have a taste for moodier images than most people I guess -- so if you had exposed normally, now your negative would be technically underexposed if the final look becomes brighter. So overexposing gives you more leeway for people changing their minds in post. So often I've been thankful that I went for a dense negative when the director starts brightening everything in post. I'm not one of those people who feel that underexposing forces the producers and director to keep the footage dark -- instead, most of the time they will lighten it anyway and live with a lot of noise/grain.
  • 0

#9 Delorme Jean-Marie

Delorme Jean-Marie
  • Basic Members
  • PipPipPipPip
  • 513 posts
  • Cinematographer
  • paris, france

Posted 12 October 2008 - 01:34 PM

thanks gentlemen sometime it's better asking yourself simple questions rather than staying in the dark
  • 0


Visual Products

Rig Wheels Passport

Media Blackout - Custom Cables and AKS

Aerial Filmworks

Wooden Camera

Abel Cine

Gamma Ray Digital Inc

CineLab

Opal

FJS International, LLC

Paralinx LLC

CineTape

Willys Widgets

The Slider

Broadcast Solutions Inc

rebotnix Technologies

Ritter Battery

Glidecam

Metropolis Post

Technodolly

Tai Audio

Gamma Ray Digital Inc

Wooden Camera

Visual Products

Tai Audio

CineTape

The Slider

Technodolly

FJS International, LLC

Willys Widgets

Media Blackout - Custom Cables and AKS

Paralinx LLC

Abel Cine

Aerial Filmworks

Opal

Ritter Battery

Broadcast Solutions Inc

CineLab

rebotnix Technologies

Glidecam

Metropolis Post

Rig Wheels Passport