Jump to content


Photo

Light meter settings for video


  • Please log in to reply
10 replies to this topic

#1 Brandon151

Brandon151

    New

  • Basic Members
  • Pip
  • 4 posts
  • Cinematographer

Posted 27 February 2007 - 01:57 PM

In metering for video, what are my lightmeter settings as far as ISO, and shutter speed. I'm using the variCam, shooting 24p at 1/48 - 1/60 shutter. Do I need to set the FPS setting on my Sekonic Cine Light Meter, as I am shooting the 24p mode?
  • 0

#2 Michael Nash

Michael Nash
  • Sustaining Members
  • 3330 posts
  • Cinematographer
  • Pasadena, CA

Posted 27 February 2007 - 06:23 PM

The proper "setting" for your meter when shooting video is back in its case. ;)

You determine exposure with a monitor, a waveform monitor (if you have one), and the zebra stripes. You'll drive yourself crazy, chasing your tail if you try to use your meter to determine exposure, since video exposure is dependent upon more things than a fixed ASA and frame rate. Use your meter for lighting if you like, but then it doesn't matter what ASA it's set to because it won't always correspond to the lens anyway.

Video cameras can be set up any number of ways, giving different sensitivities as well. Check here for some rough ASA shutterspeed equivalents.
  • 0

#3 Daniel Carruthers

Daniel Carruthers
  • Basic Members
  • PipPipPipPip
  • 334 posts
  • Cinematographer
  • Canada

Posted 27 February 2007 - 11:15 PM

I agree for the most part. You should have a monitor and wave forms on set. But I like using my meter.
I work on small indie productions, where im usually away from the camera helping set up the lights, and I love being able to take a reading and know the ratio from all my key lights to fill, before i even look into the camera.
Ive never worked with the varycam, so i cant give you the asa. But i own a sekonic meter myself,and i keep the framerate at 24. And yes for the most part its not very accurate,but the more you use your meter and the more familiar you are with the camera, you'll know what asa to keep your meter at.
  • 0

#4 Melatur Sundaresan

Melatur Sundaresan

    New

  • Basic Members
  • Pip
  • 2 posts
  • Cinematographer

Posted 28 February 2007 - 02:12 AM

In metering for video, what are my lightmeter settings as far as ISO, and shutter speed. I'm using the variCam, shooting 24p at 1/48 - 1/60 shutter. Do I need to set the FPS setting on my Sekonic Cine Light Meter, as I am shooting the 24p mode?

Hello Brandon,
From a technically correct perspective, the sensitivity of a video camera is defined as the amount of LUX required from a 3200K source at a given Fstop (Tstop?) at which a 89% reflectance white card produces 100 IRE (Or 1V) on a Wave form Monitor. So, using an incident light meter in video involves:
A) Reading only in Lux Units( 10.76 Lux=1F.C)
B) Using the flat Disk on your meter.
Take a Chip Chart, light it up evenly, White Balance camera to a perfect 3200k, connect it to Wave form, see where the white touches 100 ire on it. You may zoom in to only the whites if you want. The aperture setting at which that happens is the sensitivity. So if a 1000 LUX gives F-4, then your quasi-ISO rating would be 200ASA(ISO)for 3200k. Working with the Sony D-790 or D-50, I try to get around 500 LUX. That way i end up shooting at F4 or 5.6 whatever the grey tone of the subject is.
A much simpler way would be to download the camera manuals from the company's website to find out the sensitivity is, knock about 15% off it & assume that is the sensitivity!
  • 0

#5 Michael Nash

Michael Nash
  • Sustaining Members
  • 3330 posts
  • Cinematographer
  • Pasadena, CA

Posted 28 February 2007 - 04:04 AM

From a technically correct perspective, the sensitivity of a video camera is defined as the amount of LUX required from a 3200K source at a given Fstop (Tstop?) at which a 89% reflectance white card produces 100 IRE (Or 1V) on a Wave form Monitor. So, using an incident light meter in video involves:
A) Reading only in Lux Units( 10.76 Lux=1F.C)
B) Using the flat Disk on your meter.
Take a Chip Chart, light it up evenly, White Balance camera to a perfect 3200k, connect it to Wave form, see where the white touches 100 ire on it. You may zoom in to only the whites if you want. The aperture setting at which that happens is the sensitivity.


This technique may provide a standard of reference for comparing cameras, but doesn't mean much for determining a working ASA (exposure needed for proper midtones). As soon as you change the knee settings, dynamic range, or gamma preset all that goes out the window, as it changes the relationship between highlights and midtones.
  • 0

#6 Melatur Sundaresan

Melatur Sundaresan

    New

  • Basic Members
  • Pip
  • 2 posts
  • Cinematographer

Posted 28 February 2007 - 08:27 AM

This technique may provide a standard of reference for comparing cameras, but doesn't mean much for determining a working ASA (exposure needed for proper midtones). As soon as you change the knee settings, dynamic range, or gamma preset all that goes out the window, as it changes the relationship between highlights and midtones.

Hello Michael,
When working on Video, One does not need(cannot have) a "working ASA" which is why I said that it gives a "Quasi ASA". Working with a flat disk, you are using the light meter as an incident light meter (as opposed to using it as an exposure meter) & there is no harm in knowing the amount of LUX/F.Cs (and hence the probable aperture one will be working at) before setting up camera. I have found it to be useful when shooting interviews in available light indoors & when doing multicamera jobs i have used meters to set Key/Fill ratios "in the ball-park". All this can be done when cameras are being cabled up to waveforms & monitors (when not working in readymade studios). Also, doesn't one change Knee settings, gamma & Blacks after setting a base aperture?
Ofcourse, all of the above does not in any way change either the relevance or correctness of what you have said.
One mistake I have made in my earlier post is that the required change is not 15% but 33% or a third of a stop.
  • 0

#7 Michael Nash

Michael Nash
  • Sustaining Members
  • 3330 posts
  • Cinematographer
  • Pasadena, CA

Posted 28 February 2007 - 06:42 PM

Also, doesn't one change Knee settings, gamma & Blacks after setting a base aperture?


Not necessarily. Usually when shooting dramatic work you'll program a "look" into the camera that you'll use throughout most of the shoot, just as you might select a certain filmstock when shooting film. In the case of the Varicam, changing the gamma preset and dynamic range can change the exposure of the image dramatically. You generally shape your overall gamma curve first and expose for that, making adjustments to fine-tune the image afterward. You may then fine-tune exposure again, but by this time the relationship between a camera's native sensitivity and proper exposure can be off by one stop or more.


Working with a flat disk, you are using the light meter as an incident light meter (as opposed to using it as an exposure meter) & there is no harm in knowing the amount of LUX/F.Cs (and hence the probable aperture one will be working at) before setting up camera.


That's my point; the "probable aperture" can vary dramatically depending on the camera's programming. Your technique for determining a camera's native sensitivity is not wrong -- I'm just trying to point out that the range between 100% white and 50% can vary, and if you want to estimate a shooting stop relative to the rendering of midtones (as you do when using a light meter), then using the camera's sensitivity at 100% white could cause your estimate to be off by one or more stops.

Again, there's nothing wrong with knowing the ballpark sensitivity of the camera (and programming) you're using, for the purpose of roughing in your lighting with a light meter. I do it from time to time, especially when I have to pre-light away from the camera. But it's based on how the camera renders midtones at that light level, not how it renders white. Setting the actual camera aperture of course is a different matter.
  • 0

#8 Sam Kim

Sam Kim
  • Basic Members
  • PipPip
  • 97 posts
  • Student

Posted 07 March 2007 - 10:43 PM

Setting the actual camera aperture of course is a different matter.



I'm new to digital and I've used my light meter a whole bunch for film but digital is a different beast. At this time, I don't have a waveform monitor. Two questions:

1) Can I use a waveform with a laptop, final cut pro and my camera firewired in while shooting?

2) I guess I'm confusing myself by making digital overly hard. When would one change the f/stop?
  • 0

#9 Michael Nash

Michael Nash
  • Sustaining Members
  • 3330 posts
  • Cinematographer
  • Pasadena, CA

Posted 07 March 2007 - 10:57 PM

1) Can I use a waveform with a laptop, final cut pro and my camera firewired in while shooting?


Never tried it, but if you can get a live image to read on FCP's waveform, then theoretically yes.

2) I guess I'm confusing myself by making digital overly hard. When would one change the f/stop?


Uh, when you want to make the image brighter or darker? :P Not sure what you're asking...
  • 0

#10 Sam Kim

Sam Kim
  • Basic Members
  • PipPip
  • 97 posts
  • Student

Posted 08 March 2007 - 12:13 AM

Never tried it, but if you can get a live image to read on FCP's waveform, then theoretically yes.
Uh, when you want to make the image brighter or darker? :P Not sure what you're asking...


-_- me neither necessarily. here's how I do it in film. after setting up my lights the way i want, making sure i have the ratio i want, i take a reading and get my f/stop. i'll adjust the lens for that and shoot with that for the scene. i guess what i'm asking, is it the same for digital. thinking about it now for the umptienth i don't see why not. -_-

anyway. when shooting digital is it better to shoot at a higher f stop? i'm wondering if i shoot lower on the dynamic curve of digtial i'll get more noise and pixelation. from what i tried, crushing blacks in digital is definitely not the same process as reversal. tips?
  • 0

#11 Michael Nash

Michael Nash
  • Sustaining Members
  • 3330 posts
  • Cinematographer
  • Pasadena, CA

Posted 08 March 2007 - 03:57 AM

-_- me neither necessarily. here's how I do it in film. after setting up my lights the way i want, making sure i have the ratio i want, i take a reading and get my f/stop. i'll adjust the lens for that and shoot with that for the scene. i guess what i'm asking, is it the same for digital. thinking about it now for the umptienth i don't see why not. -_-

anyway. when shooting digital is it better to shoot at a higher f stop? i'm wondering if i shoot lower on the dynamic curve of digtial i'll get more noise and pixelation. from what i tried, crushing blacks in digital is definitely not the same process as reversal. tips?


With digital (AKA "video") you do it the same way as film, except that you don't set the lens exposure by a light meter. In both cases you're lighting for the particular range of the imager (film or chip), and then selecting an exposure that's going to give you the brightnesses you want. It's the same principle.

Digital cameras don't produce any more noise in the shadow region than anywhere else in the range, as a rule. You'll only get added noise if you underexpose the image and then try to bring it back up in post. It's no different than film in that regard; underexpose and "print up" and you get noise or grain.

The shooting stop has nothing to do with noise. This seems to be a common misconception, and I'm not sure where it comes from. F-stop controls exposure. Gain controls amplification (and therefore noise). If the gain is set to zero db, you won't have any more noise at f/2 than you would at f/22, just a different exposure. If anything, with smaller-chipped digital cameras you usually try to shoot at the widest aperture possible to minimize depth of field. But with 1/3" or 1/4" chips, there's only so much you can expect.

Reversal film is more contrasty throughout its entire range, not just in the blacks. If you want to emulate a reversal film look with DV footage, you need to play with both the highlights and shadows, as well as the color saturation.
  • 0


The Slider

Opal

Technodolly

Tai Audio

Rig Wheels Passport

Visual Products

Aerial Filmworks

FJS International, LLC

Metropolis Post

Broadcast Solutions Inc

Paralinx LLC

rebotnix Technologies

Ritter Battery

Willys Widgets

Abel Cine

Wooden Camera

Gamma Ray Digital Inc

Media Blackout - Custom Cables and AKS

Glidecam

CineLab

CineTape

Gamma Ray Digital Inc

Visual Products

Ritter Battery

Metropolis Post

Aerial Filmworks

Glidecam

Paralinx LLC

Media Blackout - Custom Cables and AKS

Willys Widgets

Wooden Camera

Broadcast Solutions Inc

CineLab

The Slider

Rig Wheels Passport

Technodolly

CineTape

Abel Cine

Opal

Tai Audio

rebotnix Technologies

FJS International, LLC