Jump to content


Photo

ND vs Shutter speed


  • Please log in to reply
17 replies to this topic

#1 Murali Pallikonda

Murali Pallikonda
  • Basic Members
  • PipPip
  • 10 posts
  • Cinematographer

Posted 01 April 2009 - 07:34 AM

All,

I came across a DP who says usage of ND not only decreases light, but also increases contrast on actors's faces. He prefers to use ND .6/.9 and then closes shutter to bring down the exposure.

In case of shoot with Red One in 4K, does this pose any new issues ?
Would the footage look too much video, as there is no blur at all ?

Thanks in advance,
Murali
  • 0

#2 Adrian Sierkowski

Adrian Sierkowski
  • Sustaining Members
  • 7117 posts
  • Cinematographer
  • Los Angeles, Ca

Posted 01 April 2009 - 07:50 AM

simply put, ND controls exposure, shutter speed controls motion. While you could change shutter speed to change exposure you are also changing how motion appears on the camera. And I don't think ND will bring up exposure?
  • 0

#3 David Rakoczy

David Rakoczy
  • Basic Members
  • PipPipPipPip
  • 1579 posts
  • Cinematographer
  • USA

Posted 01 April 2009 - 08:19 AM

All,

I came across a DP who says usage of ND not only decreases light, but also increases contrast on actors's faces. He prefers to use ND .6/.9 and then closes shutter to bring down the exposure.

In case of shoot with Red One in 4K, does this pose any new issues ?
Would the footage look too much video, as there is no blur at all ?

Thanks in advance,
Murali




When using NDs you OPEN the Iris.. not close down.. NDs decrease the amount of light traveling through the Lens. They do not increase contrast as they are Neutral Density (ND). They are in effect, perfect sun glasses for your Camera. NDs are used to bring light levels down to an acceptable (or preferrable) level for your Film Stock and Lens choice. They are also used to lessen the Depth of Field.

FILM LIGHTING

PHOTOGRAPHER'S GUIDE TO USING FILTERS

Shutter Speed controls blur (or the lack of) for the most part .
  • 0

#4 Brian Drysdale

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

Posted 01 April 2009 - 08:49 AM

I've seen the contrast on a lenses improving (increasing) when it's stopped down, but not when you open the aperture as when using ND filters. The degree of this effect will vary from lenses to lenses and on high quality glass may not be that noticeable in practise.

With the RED you'll need the denser ND filters when shoot daytime exteriors.

As has been said, the shutter will effect the motion blurring and it can get quite stroby if the angle is deceased too much.
  • 0

#5 Murali Pallikonda

Murali Pallikonda
  • Basic Members
  • PipPip
  • 10 posts
  • Cinematographer

Posted 01 April 2009 - 09:07 AM

Thanks Adrian. I didn't mean to say ND increases exposure. Sorry if my post gave that impression.
Thanks David, Brian. I always use 1.2 ND with Red due to it's 320 ASA rating and some times more.
Based on the shutter angle calculations, halving the angle decreases exposure by one stop and hence going from 180 degrees to 45 degrees, exposure can be reduced by 2 stops. Is there a minimum angle below which image gets messed up ?
  • 0

#6 Brian Drysdale

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

Posted 01 April 2009 - 09:43 AM

Thanks Adrian. I didn't mean to say ND increases exposure. Sorry if my post gave that impression.
Thanks David, Brian. I always use 1.2 ND with Red due to it's 320 ASA rating and some times more.
Based on the shutter angle calculations, halving the angle decreases exposure by one stop and hence going from 180 degrees to 45 degrees, exposure can be reduced by 2 stops. Is there a minimum angle below which image gets messed up ?


Personally, I start to really notice the shutter effect beyond 90 degrees although even then you do notice it on any faster movement.

I seem to recall 45 degrees as the angle used on "Saving Private Ryan".
  • 0

#7 John Sprung

John Sprung
  • Sustaining Members
  • 4635 posts
  • Other

Posted 01 April 2009 - 10:18 AM

In case of shoot with Red One in 4K, does this pose any new issues ?


ND is definitely better. Closing down the shutter reduces motion blur, which destroys the illusion of motion. You can use that (hopefully rarely) as an effect if you want, but it's definitely not for general purpose shooting.

There's a specific issue using ND on the Red. Most ND filters are neutral only for visible light, but pass a lot of infra-red. The Red is unique among electronic cameras in that it has a lot of IR sensitivity. So, you need to get special ND's that also block IR. Tiffen and Formatt have them. Or, if you want another weird effect, hang as much conventional ND as you can, like maybe 3.6 or 4.8, and your Red is now an Infra-Red camera.




-- J.S.
  • 0

#8 Scott Fritzshall

Scott Fritzshall
  • Basic Members
  • PipPipPipPip
  • 584 posts
  • Other
  • Los Angeles

Posted 01 April 2009 - 10:31 AM

The image never really gets "messed up," you just progressively get less and less motion blur, and eventually you start cutting down light so much that you run out, even in bright sunlight. The smallest shutter I've seen was 11 degrees- the image itself still looks totally normal, but in motion it's very stuttery. This was for a music video, and the goal was to get something that looked intense, so it worked pretty well. But yeah, you probably don't want to shoot a dinner conversation scene like that.
  • 0

#9 John Sprung

John Sprung
  • Sustaining Members
  • 4635 posts
  • Other

Posted 01 April 2009 - 10:37 AM

The image never really gets "messed up," .....


Except that there's no way to fix it in post. Shoot with a short shutter, and you'll have to re-shoot to fix the problem.




-- J.S.
  • 0

#10 Murali Pallikonda

Murali Pallikonda
  • Basic Members
  • PipPip
  • 10 posts
  • Cinematographer

Posted 01 April 2009 - 11:14 AM

Thanks for the clarification, folks. Appreciate it very much.
I used Formatt 1.2 Hot Mirror ND filter with pretty good results so far (with 180 degree shutter).

Murali
  • 0

#11 Scott Fritzshall

Scott Fritzshall
  • Basic Members
  • PipPipPipPip
  • 584 posts
  • Other
  • Los Angeles

Posted 01 April 2009 - 01:57 PM

Except that there's no way to fix it in post. Shoot with a short shutter, and you'll have to re-shoot to fix the problem.

Well, I'm going under the assumption that if you shoot with an 11 degree shutter, you're doing it on purpose, and thus it's not a problem that needs fixing. Obviously if you want it to look anywhere close to "normal," then it's a problem.

And technically you probably could re-add a fairly accurate simulation of motion blur with an optical flow tool such as Kronos, as well as a ton of rotoscoping and a lot of processing time, but clearly that's kind of a silly solution when you could just shoot it the way you want to begin with.
  • 0

#12 John Sprung

John Sprung
  • Sustaining Members
  • 4635 posts
  • Other

Posted 01 April 2009 - 04:08 PM

Well, I'm going under the assumption that if you shoot with an 11 degree shutter, you're doing it on purpose, and thus it's not a problem that needs fixing.


Ah, but remember the original question. If somebody thinks that short shuttering is just a substitute for ND, they'll get themselves in a world of hurt where a re-shoot is the only real way out.





-- J.S.
  • 0

#13 Scott Fritzshall

Scott Fritzshall
  • Basic Members
  • PipPipPipPip
  • 584 posts
  • Other
  • Los Angeles

Posted 01 April 2009 - 04:17 PM

Well I suppose I'd hope that a DP would be aware of what effect changing the shutter had and would take that into account when making his decision, but I guess you never know...
  • 0

#14 John Sprung

John Sprung
  • Sustaining Members
  • 4635 posts
  • Other

Posted 01 April 2009 - 04:38 PM

.... but I guess you never know...


Yup, we get all kinds here. All the way from high school to the ASC.





-- J.S.
  • 0

#15 Murali Pallikonda

Murali Pallikonda
  • Basic Members
  • PipPip
  • 10 posts
  • Cinematographer

Posted 02 April 2009 - 02:35 AM

Personally, I'm not keen on going with shutter method for exposure reduction. We will be doing extensive tests before we think of going with that option. I wanted to be prepared regarding what I can expect from the testing.
As usual, your answers were very helpful, thanks much.

Murali
  • 0

#16 Keith Walters

Keith Walters
  • Sustaining Members
  • 2219 posts
  • Other
  • Sydney Australia

Posted 02 April 2009 - 04:21 AM

All,

I came across a DP who says usage of ND not only decreases light, but also increases contrast on actors's faces. He prefers to use ND .6/.9 and then closes shutter to bring down the exposure.

In case of shoot with Red One in 4K, does this pose any new issues ?
Would the footage look too much video, as there is no blur at all ?

Thanks in advance,
Murali

Well that's a coincidence. I couldn't work out where to put this thread because hardly anybody seems to visit the RED forum any more. It would have fitted nicely into this discussion. Anyway, it might give you some insight into the problems with filters designed before there were single-chip HD cameras.
  • 0

#17 Joe Giambrone

Joe Giambrone
  • Basic Members
  • PipPip
  • 98 posts
  • Director

Posted 05 April 2009 - 12:37 PM

If you use ND more than 1 stop, be sure to look into hot mirror reflective filters. Otherwise infrared radiation can turn your blacks purple. This effect can happen on other cameras, but the Red forums discuss the issue in several threads. Some filters are ND with mirror, in various densities.
  • 0

#18 John Sprung

John Sprung
  • Sustaining Members
  • 4635 posts
  • Other

Posted 06 April 2009 - 02:47 PM

Otherwise infrared radiation can turn your blacks purple.


Always test. Because you can't see IR, that's the only way to know what it'll do. Results from one setup may not match another. Fortunately, you can see stuff immediately with electronic cameras.




-- J.S.
  • 0


Rig Wheels Passport

Aerial Filmworks

Paralinx LLC

The Slider

CineLab

FJS International, LLC

Gamma Ray Digital Inc

Metropolis Post

Opal

Tai Audio

Abel Cine

Technodolly

Willys Widgets

Glidecam

rebotnix Technologies

Ritter Battery

CineTape

Broadcast Solutions Inc

Wooden Camera

Media Blackout - Custom Cables and AKS

Visual Products

Gamma Ray Digital Inc

rebotnix Technologies

Visual Products

Rig Wheels Passport

Abel Cine

Ritter Battery

Aerial Filmworks

Opal

Willys Widgets

Media Blackout - Custom Cables and AKS

CineTape

Wooden Camera

CineLab

Glidecam

FJS International, LLC

Metropolis Post

The Slider

Broadcast Solutions Inc

Technodolly

Paralinx LLC

Tai Audio