Exposure practises

gunleik

gunleik

Well-known member
Finally I have it, and I'm starting to play around.
Fun.
But I'm also running into the same problems as it looks like most people do.
I've been playing around with exposures and zebra settings a little bit, and wonder how much light you guys let this little charm get.

At 80% zebra I find the images generally noisy, but I might be wrong, (still in early testing stages) I'm viewing on the Panny 17" through SDI from Decklink in Final Cut Pro. But then again - the 17" is a world of its own for me to grasp, too.

So question is:
What Scene files/exposure practises have you guys developed for HD?

Gunleik
 
gunleik said:
[...] What Scene files/exposure practises have you guys developed for HD? [...]
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The exposure practice I use with HD is the same as any other video camera, except the DVX, HVX and Varicam have one very special feature that most cameras do not which makes exact exposures easier: the spot meter. When you turn the marker feature on (you toggle through it using the Zebra button) the little square inside the big square in the middle of the viewfinder is the area that is being measured by the spot meter with the "exposure" values (actually video lumniance levels) indicated in the lower-left side of the viewfinder, from 0% to 99^%.

So you now have a way to determine exactly where in the tonal scale from black with no textural detail (0) to dark grey (15-25) to middle grey (45-55) to light grey (66-75) to complete white with no textural detail (99^) any particular part of the scene is. If you want to create an image with the minimal of noise, make sure you have gain set to 0 and at least some areas of the scene in pure black. In terms of scene file settings, I like to set the master pedestal down a bit (like -4 to -6 or so, it's a "salt to taste" kind of thing), to assure your blacks are really black, so I bring the master pedestal down until pure black (lens cap on) reads 0%. This avoids murky blacks in the image.

Now you can use the spot meter to place your shadows in the 10 to 30 IRE range, your mid tones (18% grey if you have a photo background) around 45 to 55 IRE, your highlights with textural detail in the 70-80 range, and you can determine easily than anything over 90 is pure white. This allows you to tweak your lighting to suite your needs.

In situations like the following where you don't have control of the lighting:



The spot meter is especially handy, as you can accurately determine the exposure checking various points in the scene and see where they lie in the range. The spot meter is almost as good as having a waveform monitor with you, a critical component for getting perfect exposure in video. The above image was shot with an HVX200 with Cine Gamma and Cine color matrix and I placed the spot meter on the silver platter close to the window, than should show some textural detail, and I adjusted the iris so the brightest highlights on the platter were right at 100. Then I checked my shadow areas, and fine tuned a little, bring the exposure up a notch, allowing a small portion of the platter to be at the 99^ reading. Had I been doing lighting, I could have used the spot meter to accurately determine how much light I needed to bring something out of the shadow, but not be murky, by placing it around 15 to 25.

The marker is one of the most amazing features of the HVX and DVX, anyone who studied the Zone System in a photo class will really take to this. The problem with Zebras is that they are "high water markers" but don't tell you important information about your shadows. Having some solid black in the frame helps reduce the perception of noise in the shadows. But at the same time you want to make sure that elements that are critical to see are sufficiently lit to clearly see details, above 15 or so. The zebras in the HVX are better than most, allowing you to choose anything from 50 up to 100, so you can use them as an indicator of highlights without detail (100) and mid-tones of the scene (50), most other cameras don't let you bring a zebra so low. While I use the zebras a lot, if I have the option, it's nice to use a Sony PVM series field monitor (properly calibrated to bars and re-calibrated every time the ambient light situation around the monitor changes) and a waveform monitor for even more precise exposure determination. The LCD on the camera, as far as I'm concerned, is good for three things: (1) framing the shot, (2) focusing ith the focus assist, and (3) using the spot meeter. For accurate, perfect, exposure, in spot meter I trust.

Note: if you want to see the original DVCPRO HD frame that the above image was made from, here's a two frame QuickTime movie: http://www.kino-eye.com/wp-content/uploads/2006/02/HVX200-First-Look.mov (472 KB, DVCPRO HD codec) with the above frame and a related frame (a close up of the power supply voltage meter).
 
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Thank you SOOOO much for your time and detailed answer!

I can hardly say how much this apprechiated!

Gunleik
 
Damn David, that has to be one of the most informative posts I have read here in a long time.

Thank you.

Jim
 
That is an amazing answer and really great info! Also, based upon Barry's run and gun scenerio... I set my zebras to 105 percent and when it hits the zebras just a bit then I know I have pushed the exposure to the limit and everything looks well exposed and not too dark or noisy...


Maybe David should have a seperate thread about this with some photos and pics explaining it all.. Really does look so valuable for controlled stuff. I woud also recommend the 105 percent zebras when you have no time and just have to run and go... Has been very reliable so far.
 
wow!

wow!

Wow, been using the dvx for a long time and foolishly never have taken advantage of the marker (never knew how to use it - never mind finding the damn thing). Haven't been happy with the lack of expose metering/control on the dvx compared to my other cameras - well, now I know why. Thank you for the enlightenment.
 
why do they only allow you to set zebra's at 50 for the lowest? If you could set it lower, seems like their could be some beneficial uses for checking shadows. id like to know how dark parts of the image may be in certain circumstances.
 
I nominate David's post as post of the year. That was really great. Thanks a lot!

The other thing I've noticed is that this camera is great at holding the highlights. So, Barry's comment about the 105 zebra setting is right on. I've actually been able to pull data out of a blown out portion of video using the color corrector in FCP. It blew my mind! Anyone else have a similar experience? Or is my HVX special?
 
Don't forget to set FCP to super white so your highlights don't get clipped. The HVX will record nice info up there but your editor is just as happy to cut it right off. Note that some quicktime formats don't go past 100 so you may have to bring your highlights down before outputting your movie.
cheers,
Sam
 
baquajim said:
Damn David, that has to be one of the most informative posts I have read here in a long time [...]
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darwinandpaine said:
I nominate David's post as post of the year. That was really great. Thanks a lot! [...]
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*blush* I appreciate your comments :dankk2: I love this place too... I've learned so much...
 
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darwinandpaine said:
[...] I've noticed is that this camera is great at holding the highlights. So, Barry's comment about the 105 zebra setting is right on. I've actually been able to pull data out of a blown out portion of video using the color corrector in FCP. It blew my mind! Anyone else have a similar experience? [...]
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Yup, the camera gives you a little bit extra at the top, nice to have a bit of margin of error, reminds me of that scene in This Spinal Tap, "it goes up to 11..."
 
ggdelarge said:
why do they only allow you to set zebra's at 50 for the lowest? If you could set it lower, seems like their could be some beneficial uses for checking shadows. id like to know how dark parts of the image may be in certain circumstances.
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I think this is historic, typically Zebras have been used in ENG (news gathering) settings and remember that professional video cameras have mostly catered to the broadcasters, where you're in a rush and all that counts is to make sure that the faces of your subjects are OK and highlights are not excessively blown out, thus the "high water mark" thinking, and if you compare it to photography, exposing video is much like exposing reversal film... you try to avoid excessive overexposure. Now DV Rack has a cool feature, "Black Zebras" for just that purpose... lettting you know your "low water mark" in the shadows, but since historically people using video in controlled settings have simply used a Waveform monitor, there's not been much demand for spot meters and wider range Zebras, but starting the the Varicam (the first video camera I ever used that I actually liked) it seems like Panasonic has been listening to camerapeople... so we got things like variable frame rates, film record mode, cine gamma, cine color matrix, spot meter, etc years ago in the Varicam (how many 5 year old video cameras continue to perform at the top of their class like the Varicam does?) and now we're getting all this trickle down technology in the HVX, the righteous son (or daughter, take your pick) of the Varicam...
 
cinemakinoeye said:
Having some solid black in the frame helps reduce the perception of noise in the shadows.
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That's an interesting concept. Could you elaborate any on that? ...and thanks for the excellent post!
 
Cine...'s most has pretty much everything covered. I also find the mark setting absolutly fantastic especially with the HVX200 since I have to be more careful of noise.

If noise is a big deal you are also going to want to lower the detail and up the detail coring (though it will give you a softer image).

Barry is also right about the 105%. Panasonic really does give you a little extra and this is important to know. My last film I shot on a DVX100A I wanted the windows to totally blow out so I could easily key them out in Combustion. I initally set the strips on 105% but, at the last minute, got nervous and set them back down to 100%. When I pulled up my footage sure enough there was still detail in the windows and it made keying a pain. The moral? Barry knows all.
 
Just a quick question, if I were spot metering caucasian skin, would I want to be around the 55 IRE Zone? And for dark skin, the lower part of the range, 45 IRE?
 
R Gale said:
That's an interesting concept. Could you elaborate any on that? ...and thanks for the excellent post!
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Without getting into the details of human visual perception, imagine a milky frame with no black reference... you notice the noise in the shadow areas more... but if there are significant areas in the frame that a solid black, then those areas that do have noise constitute a smaller percentage of the frame and you're not using those areas as your black reference. This is not a correct scientific explantion, if there are any Physiological Psychology experts out there, I'd love to hear the scientific version...
 
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