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Waveform Monitor w/ HD?


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#1 Marc Levy

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Posted 08 September 2006 - 02:23 PM

Another HD question:

Blain Brown, in his book Cinematography: Theory and Practice asserts that a waveform monitor "is your light meter" for hi-def, and that "lighting to the monitor can lead to disaster." Do you hi-def shooters find this to be true? Do you use a waveform monitor when shooting HD? I don't hear much talk about this procedure in practice, only in books.

Thanks,
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#2 Brian Dzyak

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Posted 08 September 2006 - 04:31 PM

Another HD question:

Blain Brown, in his book Cinematography: Theory and Practice asserts that a waveform monitor "is your light meter" for hi-def, and that "lighting to the monitor can lead to disaster." Do you hi-def shooters find this to be true? Do you use a waveform monitor when shooting HD? I don't hear much talk about this procedure in practice, only in books.

Thanks,



Lighting to any monitor isn't necessarily a good idea. It can get you in the ballpark, but because all monitors tend to "look" differently no matter how well they are set up, there is no definitive way to say that what you see on set will be what comes out on the other end at post.

That said, I personally don't use a waveform for the things I shoot and nobody has complained. :) More to the point, I can generally get the pictures I'm after (exposure, color balance) because of A) just plain experience and B ) I know how I've set up my camera. As long as I'm aware of the "baseline" settings that give me "X," then I'm free to start changing things a little bit here and there confident of what will happen. Of course if we want to do something really out of the ordinary, I wouldn't dare A) do it out in the field due to time constraints...I'd insist on a setup/testing day, and B ) I'd definitely have a waveform and a large monitor available.

The key to not needing a waveform or a large monitor is being confident in the initial setup of the camera. The same principle applies with old BetaCamSP cameras or even filmstocks. Once one has experience with a given medium, you don't have to rely so much on some "checks" that would confirm what you probably already know.

But heck, if you've got the time to put one up and it helps, then why not? :)
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#3 Bob Hayes

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Posted 08 September 2006 - 08:12 PM

I live by the waveform. It tells you what you are really getting. You monitor could be and often is totally off. The better and more informed I get the more I enjoy its presence. Now The vector scope is starting to look pretty good.
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#4 John Tipton

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Posted 18 September 2006 - 05:22 PM

I use the Panasonic LH-900p lcd monitor. I has a built in waveform feature which is REALLY useful. You can just pop it up whenever you want.

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#5 Marc Levy

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Posted 18 September 2006 - 05:40 PM

Any good guides on how to best use the WF monitor?

Thanks.
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#6 John Tipton

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Posted 19 September 2006 - 12:40 AM

Any good guides on how to best use the WF monitor?

Thanks.



It's not too complicated, but I'm not sure where a good refernce might be found.

anyone?

john
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#7 Kevin Zanit

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Posted 19 September 2006 - 01:00 AM

When I have a good DIT and good viewing conditions I use the monitor (assuming it is a good one) more than the waveform.

The waveform, at least for me, is good for checking for the extremes in the image, but the monitor allows me to get more subtle than I could from just a waveform alone.


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#8 Mitch Gross

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Posted 19 September 2006 - 11:00 PM

The waveform is a wonderful thing. Saying you don't need it is like saying you don't need a lightmeter. Now there are certainly times when I in fact do not need a lightmeter, and one's eye certainly does get attuned to a level of exposure and the performance of a monitor. But that doesn't mean that I'd throw away my tools. It is especially important to use a waveform when shooting dramatic or dark scenes. It is all too easy to lower the exposure into a bootom of the toe and loose all your information. I second the use of the Panasonic LCD screens with their built in waveforms. Very useful. I also like that Panasonic cameras (even the little DVX100!) have the "Y Get" function which is a spotmeter reading in IRE. That is an invalueable tool to me.
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#9 Eric Steelberg ASC

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Posted 19 September 2006 - 11:10 PM

I usually never take my meter out of its case when I'm shooting HD. A waveform tells you so much more. After a while, like film, you can light by eye once you set your key. Then a quick glance at the monitor can confirm everything.

The main reason I dont look at the monitor while I'm lighting:

Everyone else thinks they can do the same thing, then I get other people suggesting what I should do, how the light should be. If I don't pay attention to the monitor, people assume if it's not good enough for me, it's not good enough for them...and the waveform looks too cryptic to them. So I get less questions and comments. All psychological.


I find that people who poo-poo them don't understand them or how to use them, which in many ways are easier to read than a meter.
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#10 Guy Jackson

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Posted 11 December 2006 - 10:55 PM

[quote name='Eric Steelberg' date='Sep 19 2006, 11:10 PM' post='128493']
I usually never take my meter out of its case when I'm shooting HD. A waveform tells you so much more. After a while, like film, you can light by eye once you set your key. Then a quick glance at the monitor can confirm everything.

Totally agree Eric
There is really no need to use the light meter while shooting HD unless you are trying to impress somebody :-).
Once you know your ballpark between the highlights and blacks you just play with it.
Personally I hate Zebra so it’s always off in my VF and once in a while I’ll look at the waveform just to get an idea that I’m still where I want to be.
Speaking about VF I really wish the Varicam gave us the option to move some of the info on the top of the frame (shutter angle etc…) to the bottom, I always find it as an “too much information” scenario in the worst place ever.
Anyone at Panasonic hear us?

Edited by Guy Jackson, 11 December 2006 - 10:55 PM.

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#11 Phil Rhodes

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Posted 12 December 2006 - 08:07 AM

Hi,

Having "grown up" with zebra stripes I find I'm lost without them. Habitually have a 95% zebra on, not so much because I have any particular idea that it's the useful place to have it for anyone other than me, more that I just have it baked into my brain where everything else should fall.

Whatever you do, waveform or zebras, what you're doing is giving your eye an absolute reference.

Phil
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#12 william koon

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Posted 16 December 2006 - 05:10 AM

Hi,

Having "grown up" with zebra stripes I find I'm lost without them. Habitually have a 95% zebra on, not so much because I have any particular idea that it's the useful place to have it for anyone other than me, more that I just have it baked into my brain where everything else should fall.

Whatever you do, waveform or zebras, what you're doing is giving your eye an absolute reference.

Phil


Can somebody suggest how to read the waveform ? If I dont have the waveform monitor, can I depend on the zebra set to 100%? If I dont have the lightmeter, how do I set the contrast ratio? Please help.
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#13 Oliver Temmler

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Posted 09 January 2007 - 05:46 AM

Can somebody suggest how to read the waveform ? If I dont have the waveform monitor, can I depend on the zebra set to 100%? If I dont have the lightmeter, how do I set the contrast ratio? Please help.


Reading the Waveform
The luminance levels in a scene are represented as amplitude levels in a recorded video signal. More exposure outputs higher signal levels. Overexposure results in white clipping, i.e. big image areas having 100% level showing nothing but white a.k.a blown out. In analogue video, the signal amplitude is expressed as voltage or IRE units. In digital video, a set of discrete code values is used to represent the continuous luminance range. The signal range defines upper and lower limit of the video signal representing the luminance values of black and pure white (see attachment):
  • Normal range (also called legal/safe range) signals use code values between 64 and 940.
  • Extended range (also called full range) signals use code values between 4 and 1019.
Normal range is most commonly used for HD video with 4:2:2 chroma sub-sampling. Using extended range with a 4:2:2 HD format is rather unusual. Same goes for 4:2:0 or 3:1:1 formats like HD or HDV. The use of extended range mostly affects the quality of black level reproduction. Depending on the technical requirements of the production, 4:4:4 HD formats use either normal or extended range.

Using the Zebra should work just fine as well. Depending on the display size, a very small highlight blowing out might not be visible, but tiny spots of blown out highlights usually don't matter. As soon as bigger areas blow out they can be clearly seen using the zebra. If you set the Zebra to 95%, you'll see image areas that are about to blow out. If you use the Zebra before the take to check your lighting, you can set it to 99% as well I guess. I'm not a Zebra specialist, though.

Setting the contrast ratio... I don't know if I understand that question. You can either use a flat or steep gamma curve to decrease or increase contrast, or you can set your lighting to achieve the desired contrast ratio.

Hope this helps.

Attached Images

  • waveform_01.png

Edited by Oliver Temmler, 09 January 2007 - 05:49 AM.

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#14 John Lawrence

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Posted 17 January 2007 - 11:00 AM

Another HD question:

Blain Brown, in his book Cinematography: Theory and Practice asserts that a waveform monitor "is your light meter" for hi-def, and that "lighting to the monitor can lead to disaster." Do you hi-def shooters find this to be true? Do you use a waveform monitor when shooting HD? I don't hear much talk about this procedure in practice, only in books.

Thanks,




I've heard this quote before: "waveform is your lightmeter for HD/video" and I've always found it a flawed comparison. The reason is that these are tools that work in very different ways. A waveform monitor shows you luminance levels within your frame, whereas a light meter (incident) will tell you how much light is falling in a particular area of the set/location. You don't need a camera, waveform, or monitor to check your light levels with a meter. The most valuable resource you have is your eyes, and you should never light "to" your meter, but still it can be a valuable tool.

there seems to be a discussion about which is "better" to use for HD field production:
1. monitor
2. waveform
3. light meter

The truth is that all three of these tools work differently and can be very useful depending on the situation, or application. This goes for video, HD, or Film for that matter.

I learned long ago that every job is not ideal. I don't always have the luxury of staring at a monitor and waveform with my gaffer, calling it our light meter.

Consider the location where you will be shooting a round table discussion of 8-10 people at a table. Let's say the room has dark, walls. And, it's just you and a sound person. Big surprise is that they haven't hired 8-10 people to be stand-ins and they pretty much want to roll fairly quickly after "talent" arrives. Without people sitting in your frame, a waveform doesn't do you any good and the time it takes to have your sound person sit in every chair to check the lighting consistency is prohibitive.

Perfect time to pull out an incident light meter and check that an even amount of light is falling in each position. I rate most HD and Video cameras I work with around 320 ASA just as a base. I'm not using the meter to expose, because I have zeebras for that, and I have correctly set up my viewfinder so I'll have a reliable way to choose exposure. I'm just using my meter as a guide to keep my lighting even when I don't have any stand-ins to look at.

I might not pull my meter out for a few months of shooting HD, but I would pull it out in that application. In that situation, I also would not take the time to set up a waveform monitor unless I had more time and more crew.

I recently did a large green screen shoot in a studio and relied on my monitor and waveform, which my DIT had on a cart. In this situation I did not use a meter, as my waveform gave me all the luminance info I needed, and my monitor gave me a very accurate representation of color and contrast, as it was set up correctly in a controlled environment.
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#15 Thomas Cousin

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Posted 18 January 2007 - 12:08 PM

I recently did a large green screen shoot in a studio and relied on my monitor and waveform, which my DIT had on a cart. In this situation I did not use a meter, as my waveform gave me all the luminance info I needed
[/quote]


hello,

according to the waveform, where are you trying to "put" the straight line of the luminance of the green screen ?
for a given stop, when you look at your waveform and monitor, what is the best reading to obtain an efficient green screen; a screen that the fx team could use without any problems.
do you think an average , 300mV , 350mW, would give a good saturated screen. or maybe a little over, 400, 450 mV ?

it seems to me that going too high in HD may result in flaring the lens too much with green reflections, and losing the saturation.

what are you doing ?

thomas
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#16 John Lawrence

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Posted 19 January 2007 - 09:52 AM

I recently did a large green screen shoot in a studio and relied on my monitor and waveform, which my DIT had on a cart. In this situation I did not use a meter, as my waveform gave me all the luminance info I needed
hello,

according to the waveform, where are you trying to "put" the straight line of the luminance of the green screen ?
for a given stop, when you look at your waveform and monitor, what is the best reading to obtain an efficient green screen; a screen that the fx team could use without any problems.
do you think an average , 300mV , 350mW, would give a good saturated screen. or maybe a little over, 400, 450 mV ?

it seems to me that going too high in HD may result in flaring the lens too much with green reflections, and losing the saturation.

what are you doing ?

thomas


For HD, I generally try to run the green screen 1/2 stop to 1 stop below my key light (for a normal set up). I've worked with lots of editors and engineers and have found that if you are anywhere between 50 and 60 IRE on your green, you are fine. I've found you need less light on a green screen than on a blue screen, which tends to suck up more light.

I've always been a stickler to keep the green even throughout, though I have learned that this really doesn't matter as much any more. I tend to be careful in shadow areas of the green (from a full body standing on green) but have learned that if there is at least 40 IRE there, you are fine (there could even be less, but I don't push it). The truth is, if it looks green, they can key it.

The main things beyond that (and in many ways, more important): watch for green reflections in glasses, watch out for green clothing, and be careful of fly away hairs. I try to avoid using diffusion on the lens for green screen, and I make sure that I have enough stop so that I don't have part of what I'm shooting go soft.

Hope that's helpful.
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