Zebra Bars ? How Do They Work at DVinfo.net

Barrie M. Yacher · February 4th, 2003, 11:23 PM

I just bought a GL2 and set the Zebra Bars. It looks like the default setting was 90. The Bars or stripes did appear in certain places as I started taping, probably in the areas where there was white. What did the Bars or stripes tell me? I am ignorant. Can someone enlighten me?

Chris Hurd · February 4th, 2003, 11:43 PM

Hi Barrie,

I think the best short explanation is the one found on page 85 of the GL2 manual: "The zebra pattern is a series of diagonal stripes that appear in the viewfinder to highlight areas of overexposure. Use it as a guide to set the aperture (iris) and shutter speed. You can also select the pattern appearance level from 80, 85, 90, 95, and 100%."

Basically, when the zebra pattern appears, you know you're a bit overexposed, and you can take a number of steps to correct this overexposure: a). make the aperture smaller by increasing the f/stop number on the iris control wheel; b.) increase the shutter speed; c.) decrease the electronic gain, if any. Hope this helps,

Don Palomaki · February 5th, 2003, 05:35 AM

The max legal video singal is 100 IRE, anythign above 100 is likely to cause problems in a broadcast signal (e.g., spatter into the sound space). Also, as you get close to 100 (maximum brightness) you start to lose highlight detail - it all washed out. Go a bit above 100 and the camcorder starts to clip the signal. In film terms - that portion of the image is overexposed. Bit haveing part of the image overexposed may not be all bad - if it is a part you are not especially interested in - such as a bright light source refection from a metal surface or the view from a window in an interior shot.

The zebra provides a visual indication/warning of this in the viewfinder, and the operator can adjust exposure accordingly to obtain the desire effect. Allowing diffent settings for the zebra threshold allows the shooter to match the camcorde to his/her preference.

One way to use zebra is set it to 95 and then shoot with the brightest highlight in which you want image detail on the verge of showing zebra.

Ken Tanaka · February 5th, 2003, 11:03 PM

Hey Barrie,

Good to see another fellow Chicagoan on DVInfo! I grew up in your neighborhood.

Welcome to the DVInfo community!

Barrie M. Yacher · February 5th, 2003, 11:06 PM

I want to thank Chris Hurd and Don Palomaki for responding to my question about zebra bars. I will reread your answers 100 times.

Robert Knecht Schmidt · February 5th, 2003, 11:10 PM

Does anyone know what the spatial resolution of the zebra patterns are? How many adjacent pixels have to be supraliminal (above the exposure threshold) for them to be zebra'd?

(And is the zebra resolution different for the XL1S?)

Jeff Donald · February 5th, 2003, 11:22 PM

The last figure I seem to recall was a 90+% accuracy. This was for a pro B & W view finder, maybe 8 to 10 years ago. Not really extremely accurate. Thats why waveform monitors are used when you have to know about your exposure. I try to see if I have any more information on it or how it is measured.

I would think a LCD screen would have much less accuracy than a CRT also. I think that's why we are all erring on the side of caution. You can always bump your levels a little in post. but once your highlights are gone, it's all over.

February 4th, 2003, 11:23 PM	#1
Barrie M. Yacher New Boot Join Date: Feb 2002 Location: Chicago, Illinois, 3 blocks from Wrigley Field Posts: 14	Zebra Bars ? How Do They Work I just bought a GL2 and set the Zebra Bars. It looks like the default setting was 90. The Bars or stripes did appear in certain places as I started taping, probably in the areas where there was white. What did the Bars or stripes tell me? I am ignorant. Can someone enlighten me?

February 4th, 2003, 11:43 PM	#2
Chris Hurd Obstreperous Rex Join Date: Jan 2001 Location: San Marcos, TX Posts: 27,368 Images: 513	Hi Barrie, I think the best short explanation is the one found on page 85 of the GL2 manual: "The zebra pattern is a series of diagonal stripes that appear in the viewfinder to highlight areas of overexposure. Use it as a guide to set the aperture (iris) and shutter speed. You can also select the pattern appearance level from 80, 85, 90, 95, and 100%." Basically, when the zebra pattern appears, you know you're a bit overexposed, and you can take a number of steps to correct this overexposure: a). make the aperture smaller by increasing the f/stop number on the iris control wheel; b.) increase the shutter speed; c.) decrease the electronic gain, if any. Hope this helps, __________________ CH Search DV Info Net \| 20 years of DVi \| ...Tuesday is Soylent Green Day!

February 5th, 2003, 11:03 PM	#4
Ken Tanaka Retired DV Info Net Almunus Join Date: Dec 2001 Location: Chicago, IL Posts: 6,943	Hey Barrie, Good to see another fellow Chicagoan on DVInfo! I grew up in your neighborhood. Welcome to the DVInfo community! __________________ Lady X Films: A lady with a boring wardrobe...and a global mission. Hey, you don't have enough stuff! Buy with confidence from our sponsors. Hand-picked as the best in the business...Really! See some of my work one frame at a time: www.KenTanaka.com

February 5th, 2003, 11:10 PM	#6
Robert Knecht Schmidt Wrangler Join Date: Feb 2002 Location: Cleveland, Ohio Posts: 1,933	Does anyone know what the spatial resolution of the zebra patterns are? How many adjacent pixels have to be supraliminal (above the exposure threshold) for them to be zebra'd? (And is the zebra resolution different for the XL1S?) __________________ All the best, Robert K S Search DVinfo.net for quick answers \| The best in the business: DVinfo.net sponsors

February 5th, 2003, 11:22 PM	#7
Jeff Donald Warden Join Date: Mar 2002 Location: Clearwater, FL Posts: 8,287	The last figure I seem to recall was a 90+% accuracy. This was for a pro B & W view finder, maybe 8 to 10 years ago. Not really extremely accurate. Thats why waveform monitors are used when you have to know about your exposure. I try to see if I have any more information on it or how it is measured. I would think a LCD screen would have much less accuracy than a CRT also. I think that's why we are all erring on the side of caution. You can always bump your levels a little in post. but once your highlights are gone, it's all over. __________________ Jeff Donald Carpe Diem Search DVinfo.net for quick answers \| Where to Buy? From the best in the business: DVinfo.net sponsors

February 5th, 2003, 05:35 AM	#3
Don Palomaki Wrangler Join Date: Sep 2001 Location: Northern VA Posts: 4,489	The max legal video singal is 100 IRE, anythign above 100 is likely to cause problems in a broadcast signal (e.g., spatter into the sound space). Also, as you get close to 100 (maximum brightness) you start to lose highlight detail - it all washed out. Go a bit above 100 and the camcorder starts to clip the signal. In film terms - that portion of the image is overexposed. Bit haveing part of the image overexposed may not be all bad - if it is a part you are not especially interested in - such as a bright light source refection from a metal surface or the view from a window in an interior shot. The zebra provides a visual indication/warning of this in the viewfinder, and the operator can adjust exposure accordingly to obtain the desire effect. Allowing diffent settings for the zebra threshold allows the shooter to match the camcorde to his/her preference. One way to use zebra is set it to 95 and then shoot with the brightest highlight in which you want image detail on the verge of showing zebra.

February 5th, 2003, 11:06 PM	#5
Barrie M. Yacher New Boot Join Date: Feb 2002 Location: Chicago, Illinois, 3 blocks from Wrigley Field Posts: 14	I want to thank Chris Hurd and Don Palomaki for responding to my question about zebra bars. I will reread your answers 100 times.