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measuring focus for video


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#1 Mike Kaminski

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Posted 01 December 2005 - 01:31 AM

How exactly do you measure focus for video and where do you measure from? I remember being told once that measurements should be made from the tip of the lens barrel, but recently someone mentioned to me that it is in fact where the film plane would be in a normal film camera, just behind where the lens connects to the body. Just wondering what the correct method is, as the difference between these two distances can be quite severe, especially when using longer lenses.
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#2 Brad Grimmett

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Posted 01 December 2005 - 01:50 AM

You measure from the "chip" plane, which is roughly the same as the film plane. Most HD cameras have a mark for where to measure from.
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#3 Elhanan Matos

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Posted 01 December 2005 - 02:35 AM

Be really careful with this, some lenses are measured from the front element of the lens and some are marked for the imager... some (if not all) ENG style lenses are marked for the front element... while the Cine style lenses are marked for the imager (film plane).
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#4 Stephen Williams

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Posted 01 December 2005 - 03:18 AM

You measure from the "chip" plane, which is roughly the same as the film plane. Most HD cameras have a mark for where to measure from.



Hi,

If they are ENG Video lenses then you measure from the front element of the lens. Its very easy to test just set the lens to the min focus point!

Stephen
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