Egineers vs. camera people

[Marty Hamrick]

I've never really had much of a problem with exposure for video,though I think it's safe to say I've stretched it to it's limits and back.I still get puzzled from time to time when I'll set my iris for what zebras are reading (70 % IRE rule for highlights on caucasian skin)and the engineers back at the shop (if going live)or director/engineer(If multi cam)will tell me to iris up or down depending on what they're seeing on their scopes and monitors.I've seen camera monitors and zebras disagree with vectorscopes and monitors as much as 40%.Is this bad calibration?Lack of standardization?I've only noticed this recently (last 5 years or so).Before that,regardless of what camera I was using,if I set the iris by what my eye,veiwfinder and zebras read,95% there was no disagreement with the vectorscopes and monitors at misssion control.What could be happening here?

Marty

[David Mullen ASC]

They may be basing decisions on the overall signal and keeping a majority below 100 IRE while you may actually be basing the exposure on how you want the image to look.

[Marty Hamrick]

They may be basing decisions on the overall signal and keeping a majority below 100 IRE while you may actually be basing the exposure on how you want the image to look.

Could be,but what puzzles me sometimes is that I get "Talent's face looks hot".While I know my zebras are at 70 IRE in just a little of the highlights on the face.

Marty

[Mitch Gross]

Well personally I like to keep my faces closer to 50 IRE. I don't actually measure this when shooting as much as I choose to check off a monitor. When I then look at where the signal is landing on a waveform I find faces landing around 50 for brighter daytime and even lower for night scenes and some dramatic work.

 

The engineers, looking at properly tuned reference monitors and waveforms are working with vastly more information than you have in your B&W viewfinder with zebras.

[Alvin Pingol]

I don't follow the 70IRE "standard" for skin highlights either. If I do, they come out way overexposed.

 

But I agree with Mitch, I use a monitor to judge exposure, and use zebras only to see what's blowing out to white (95+IRE).

[Marty Hamrick]

I don't follow the 70IRE "standard" for skin highlights either. If I do, they come out way overexposed.

 

But I agree with Mitch, I use a monitor to judge exposure, and use zebras only to see what's blowing out to white (95+IRE).

I finally figured out how to put the two sets of zebras in the viewfinder.70 and 100 so I can keep the whites down to 100 and the highlights of the faces in the 50-70 range,70 being in the highlights.Of course much depends on the talent,dark skin vs.light skin.

Usually I'm dead on the money,just every now and then there's a discrepancy.Today I was doing a shot with the sat truck and could peek in and see the waveforms and scopes.I don't usually have that luxary.Thanks guys.

Marty

[Bob Hayes]

I like the Zebras set at 100 IRE. Then when I need to check exposure I have my talent hold a white card. And just barely roll the Zebra?s off of the white. If you really want to see what your camera is doing buy a chip chart and watch how the Zebras behave. I love using chip charts but they are expensive and fade after a couple of years.

[Michael Nash]

I shoot tons of Betacam and personally I have almost no use for 100 IRE zebras. If it's blown out, I can easily see that in the viewfinder. The knee function sometimes restores a little color to burnt out highlights that you can't see in the VF, but the signal is still up there at 100 IRE.

 

Personally I like zebras somewhere in the middle like 70 IRE as a reference for exposure. It is true that Caucasian skin comes up about 70 IRE on the key side when properly exposed, but I don't live and die by that number. Exposure of any shot is determined by the levels throughout the whole frame and not just the skin tones alone. And of course in dramatic lighting, you can put as much highlight and shadow as you want anywhere you want.

 

These days when shooting ENG (uncontrolled lighting and no monitor), I rely more and more on the viewfinder for exposure. The zebras are still there, but since skin tones are moving in and out of shadow the 70 IRE rule of thumb goes out the window. If the viewfinder is in good working order and calibrated for contrast and brightness to color bars, you can begin to trust what the image is telling you. Basically, if it looks good in the VF it won't look any WORSE in color and on a professional monitor. Sometimes you get stuck with an old camera with a crappy viewfinder, but I try to familiarize myself with the quirks of whatever camera I'm using before I roll anyway.

 

Regarding Marty's situation, it sounds like errors in the engineering might be responsible for the levels being different. But another thing I've noticed in the past few years as video cameras have included more and more internal signal processing, is that the gamma, black stretch, and knee of cameras can be wildly off from each other; far more so than in the old days when all you could adjust was white balance. IRE levels and exposure can vary between cameras, just as it would between say reversal film and low-contrast negative. The old rules of thumb for video don't always apply anymore.