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How to calculate the exposure in Panasonic HVX-202


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#1 Balu K Sharma

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Posted 27 July 2008 - 01:29 PM

Hi everybody...

am a student of BFA(photography) from India. Now am working with Panasonic HVX-202, I had a problem with exposure, how to calculate the exposure in HD cameras...
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#2 Adrian Sierkowski

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Posted 27 July 2008 - 01:39 PM

Strictly speaking video cameras don't have an exposure as film cameras do, but you can guestimate. The "proper" exposure of a video camera will depend on scene content as well as any settings messed with on the inside of the camera (looks on the HVX).
What I would do would be set the camera as you intend to shoot it and point it at an illuminated grey card, filling the frame, then set it to auto iris and take note of the reading it gives you. Should this fit what you want 18% grey to read as leave it be. If not, adjust the iris on your camera to suit your exposure want.
Then, using a spot meter, from the same position and axis of the camera, take a reading of the grey card (start by setting your meter to around 200ASA, which is where I normally find the HVX reading). If the F stop on your meter matched the camera, this is the ASA to use when guessing the exposure. If it does not, adjust the asa on your meter until such time as the F stop of the camera and the F stop on yout meter are identical or as close as can be.
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#3 Chris Keth

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Posted 27 July 2008 - 08:20 PM

Adrian has you on the right track. If you want to be really thorough, do that test in both high and low light. I find that most video cameras want to be treated a little different in bright light than they do in low light. It's also usually a little different in tungsten than in daylight.
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#4 Jonathan Bowerbank

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Posted 29 July 2008 - 06:14 PM

If one wanted to know the precise correct exposure for an 18% grey card (instead of just going by eye, as most viewfinders are different and perhaps even faulty), what do you think would be the ideal zebra level to judge that? 65% is a good skintone zebra level, so perhaps that would work. Instead of doing the auto-iris (which I've done before, but didn't care for the results) you could adjust exposure just so that 18% grey is on the brim of your 65% zebra setting.

65% is a loose guesstimation by the way, if anybody has a better suggestion from experience, do speak up :)
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#5 Adrian Sierkowski

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Posted 29 July 2008 - 06:21 PM

65% is a good place for your skintones, I normally try to keep mine just under 70, though I'd think that'd be slightly brighter than 18%. IIRC Caucasian skin should be zone VI as opposed to 18%'s zone V; maybe an IRE around 50~65%?
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#6 Tim O'Connor

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Posted 29 July 2008 - 06:52 PM

65% is a good place for your skintones, I normally try to keep mine just under 70, though I'd think that'd be slightly brighter than 18%. IIRC Caucasian skin should be zone VI as opposed to 18%'s zone V; maybe an IRE around 50~65%?




I use my light meter often with my HVX-200 but because determining a speed for the camera is going to be one that varies, because it's not linear and the same at 2.8 as it is at the other end such as you could consider the ASA of a film stock, I like to use footcandles. I find that 64 footcandles gets me a
2.8 with just about one slice of a 60-70 IRE zebra on the nose of a light caucasian face and I can work from there for tweaking for that stop or go elsewhere and quickly establish a reference that seems right rather than the way with film you could calculate the change in footcandles based on the change in stops just like in the charts.

Last year though using this method I had two caucasians next to each other. One seemed by eye to be slightly fairer skinned but his face (not sweaty or
shiny at all either) reflected a lot more light than the guy right next to him. Even when I put him further from the camera than the first guy I still threw a net up so that I could keep them looking as if they were in the same light (which they were.) At one point they were talking right next to each other, less than a foot apart, and the normal guy had the one slice of 70 IRE zebra on the noise that was my starting point for that shoot and Mr. Scotchlite next to him was all zebras.

I haven't been shooting a lot of non caucasian faces likely but I've been wanting to so that I can explore some variation in shooting skin tones.

I don't know why I have to go this far back but I remember reading in ASC magazine about when "Lethal Weapon" was shot how there were exteriors
in which Mel Gibson was in the sunlight and there was a 12K on Danny Glover, who was standing next to him, because the DP had to either bring one of them up or the other down.
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#7 Adrian Sierkowski

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Posted 29 July 2008 - 07:54 PM

I generally find there is a lot more variety in non-Caucasian skin tones then there is in Caucasians' and this stems out a lot into how they reflect light (warmly or cool). I find it best to try to start with them slightly under exposed with some CTB or CTO respectively and work from there. That's just me.
Oh, also, while not and HVX thing, I find on the Sony HDVs that I like my whites right around 85IRE so as not to clip.
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#8 Tim O'Connor

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Posted 29 July 2008 - 08:48 PM

I generally find there is a lot more variety in non-Caucasian skin tones then there is in Caucasians' and this stems out a lot into how they reflect light (warmly or cool). I find it best to try to start with them slightly under exposed with some CTB or CTO respectively and work from there. That's just me.
Oh, also, while not and HVX thing, I find on the Sony HDVs that I like my whites right around 85IRE so as not to clip.




Yeah, I agree about the spectrum. I've shot some people with really dark skin and at times there seems to be a blue tint in there or perhaps more that it seems to come out on the skin when reflecting light. It looks kind of cool.

I've been amazed at how well I've made out with some shots in the past year when I underexposed to play it safe (with the HVX-200) and then
was able to pull it back up in Final Cut Pro and they looked really nice.
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#9 Adrian Sierkowski

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Posted 29 July 2008 - 09:19 PM

You know, I've always had problems with the HVX in low light; but then again, I havn't used her enough to really know the right in-camera settings to maximize dynamic range. Normally when I have her out, it's just for a sit-down interview. Most of my Low/no Indie films have still (despite my misgivings) opted for miniDV, or HDV (which I don't mind as much) or seem to jump in for S16mm (probably because I give them a break on the camera). Sad, really; the HVX is a nice camera and changed the game a bit for indie in terms of quality-v-cost (including long term). Looks like the Sony Exs might/ought continue that.
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#10 Tim O'Connor

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Posted 29 July 2008 - 11:01 PM

You know, I've always had problems with the HVX in low light; but then again, I havn't used her enough to really know the right in-camera settings to maximize dynamic range. Normally when I have her out, it's just for a sit-down interview. Most of my Low/no Indie films have still (despite my misgivings) opted for miniDV, or HDV (which I don't mind as much) or seem to jump in for S16mm (probably because I give them a break on the camera). Sad, really; the HVX is a nice camera and changed the game a bit for indie in terms of quality-v-cost (including long term). Looks like the Sony Exs might/ought continue that.



I think that I've made out better with the camera in low light than a lot of people because I don't look to fight it too hard.
Say I'm shooting a conversation on the street at night. With a couple of small lights, I can get light in people's eyes and a couple of
good solid exposures in the frame, maybe a slash of fifty-five foot candles on one side of a face a bit lower amount of fill and the background reads
like a city background at night with rich colors from neon signs and red lights and I've got enough points in the frame so that I tend to avoid
getting a lot of noise like some people.

I've thought many hours about what it's like to sit in five footcandles of light at a bar having a deep conversation or standing on a sidewalk under an old streetlight and how hard it is to reproduce that feeling and how artificial it can look, particularly with the slower film stocks used in older movies and especially dramatic television shows that didn't take any chances and so you see a burglar in the bushes in what is supposed to be the dark but there must be 250 or more footcandles on him and that just doesn't look convincing.

Thus, I've found that some scenes are shot in I way that I admire tremendously, in barely any light, with fast stocks and yet I've come to feel that it is often necessary to use more light than I want to but that if done right it may well come closer to setting the scene effectively than in the gutsy nine and a half footcandle scene that ultimately doesn't work. I think that using a fast stock and shooting at a key of 25 footcandles on a sidewalk that would have
12 footcandles in reality is okay. Yes, it's double the amount of light but in a realm where doubling the light works and doesn't lose the background.

I was checking out the Sony today. It seems great in a lot of ways, enough so that I was backing off on my usual aversion to GOP recordings, but I was
surprised to read that it's 4:2:0. I guess somehow it was sounding so good that I was expecting 4:2:2.

Anyway, you have a girlfriend who studies painting in Italy and you think maybe you should have an HVX-200 too? Dude, that just wouldn't be fair.
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#11 Andrew Koch

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Posted 30 July 2008 - 04:21 AM

In terms of accurately finding the ASA, a waveform monitor and an 18% Greycard are very useful. There are several threads on this forum for this procedure. Make sure you have a good field monitor that is properly calibrated. This makes judging exposure much easier as well. I find the viewfinder pretty unreliable, especially outdoors. If you don't have a waveform, the zebras work ok. I did a quick test with a waveform and a chip chart to see how the zebra percentages correlate to IRE. I found that they were fairly close, but I could be wrong since the test was pretty rushed. If you can, test it for yourself.
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#12 Tim O'Connor

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Posted 30 July 2008 - 06:56 AM

In terms of accurately finding the ASA, a waveform monitor and an 18% Greycard are very useful. There are several threads on this forum for this procedure. Make sure you have a good field monitor that is properly calibrated. This makes judging exposure much easier as well. I find the viewfinder pretty unreliable, especially outdoors. If you don't have a waveform, the zebras work ok. I did a quick test with a waveform and a chip chart to see how the zebra percentages correlate to IRE. I found that they were fairly close, but I could be wrong since the test was pretty rushed. If you can, test it for yourself.




Hi Andrew. Do you find it worth it though to find and determine an ASA for a camera in this situation when the virtual ASA is going to change
depending on light levels? A lot of people rate the HVX-200 (at certain settings) at 320 but then it's more like 160 at the open end of the lens, for
example. It seems to me that since that means that you'll have to do so much extra checking of what your meter is saying if you think that you're in
that area in which your virtual ASA is responding differently, why not just avoid that altogether and find another workflow?
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#13 Adrian Sierkowski

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Posted 30 July 2008 - 09:13 AM

Tim,
As for the EX1, I was a little worried about the 4:2:0 but having seen some green screen tests of it, I'm alright with that. Plus the HDMI output can give 4:2:2 out if needed, or so I've been told.
You'd think having a painter as a girlfriend is great. . . until that one day YOU become the painting. . . But that's another story for a less public place.

As for the HVX and variable ASA meters etc, for myself I'll only be using my meter to rough in lighting. Once I get the camera up I'll be checking it against the monitors/waveform (if we have them) and doing the little tweaks. I normally like to rate her at 200/250 for this as it's not a far cry from the 160/320 you mentioned.

P.s. Anyone hear anything of the new HVX170?
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