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F-Stop, T-Stop???


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#1 Damien Andre

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Posted 09 September 2010 - 07:25 PM

why do zeiss lenses label the f-stops with a T instead?
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#2 David Mullen ASC

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Posted 09 September 2010 - 07:44 PM

why do zeiss lenses label the f-stops with a T instead?


Zeiss cine lenses should be marked in T-stops other than older models. Are the still camera Zeiss lenses marked in f-stops?
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#3 Adrian Sierkowski

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Posted 09 September 2010 - 08:44 PM

A "T" stop or Transmission Stop (or as I call them True Stops) is a measure of how much light is actually getting to the film (taking into account light loss due to the glass elements of the lens) whereas an "F" stop is determined by the size of the iris opening and the size of the lens. Now, for most intents and purposes they will be "the same," or too close to make a difference, but in reality you would set your exposure via a "t" stop and determine your Depth of Field via an "f" stop. Like I said most of the time it's nearly a non-issue as you may have a T3 lens which is an F2.8 in reality.
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