Exposure and Zebra Patterns
By Eric Huyton (Lacock Films Ltd)
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Getting the correct exposure for a video image is very much a matter of experience. But there are some tools to assist you and a few basic rules to follow which will help get your exposure spot on.
Zebra Pattern or Zebra Stripes
All professional and semi professional video cameras use an exposure guide known as 'Zebra Pattern'. These are black & white diagonal lines which appear in the viewfinder and are superimposed over areas that are at a predetermined exposure level.
Set your Zebra pattern trigger level
Most cameras allow you to decide the exposure level which will trigger the Zebra Pattern. This is a matter of personal choice. Some operators set the level to 70% which corresponds to mid tone grey. This is nice and easy to understand, but the downside is that you will nearly always have a large part of the image exposed at 70% so equally, a large part of the image will be obscured by Zebra Pattern and this can be a source of annoyance.
Some operators set the Zebra Pattern level to 95% or even 100% so that they know when parts of the image are just about to over expose and lose detail. The advantage is that you won't have Zebra Stripes covering most of your viewfinder image as in the 70% setup.
It is essential to know what level the zebra pattern has been set to in the camera you are using.
Zebra Pattern display level is adjusted in the menu as in this example screen shot from a Sony High Definition camera.
In this screen shot from the menu in a Sony Camera the Zebra 1 Detect Level is set to 95% and Zebra 2 to 100%.
Zebra 2 usually displays 'spots' over the areas exposed at the set level. These 'spots' are sometimes called 'Leopard Spots'
You can chose to display Zebra 1, Zebra 2 or both
How it looks in the viewfinder
Correct exposure:zebra 1 set to 70% Same exposure:zebra 1 set to 95%
In example 1 above, the sky is correctly exposed at 70% so the zebra stripes which are set to register at 70% appear over the sky. In example 2, the exposure is exactly the same and the iris setting has not been changed. The picture is still correctly exposed but this time the zebra detect level has been changed to register at 95% which corresponds to the bright part of the girl's face. Where you choose to set your zebra detect level is a matter of personal choice. Just make sure that you know what the detect level is set to and where this should appear in a correctly exposed picture.