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t-stops


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#1 Gabriela Castanon

Gabriela Castanon
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Posted 17 March 2008 - 07:25 AM

Hi there guys,

Please can you remind me what a t-stop is, and also when you use it.

I have been working as a stuudio camera operator for about a year, and need to refresh my memory! :)

Please can tyou also send me any links where I can find a depth of field calculator.

Thanks!

Regards,

Andrea
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#2 Dominic Case

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Posted 17 March 2008 - 05:51 PM

It wouldn't take much searching (either this site or Google) to find the answer yourself.

Here is one thread on this site, or here is what Wikipedia has to say. Or search Google for "t-stop lens aperture" or something.

Since you're here, an f/stop is a the ratio of the lens diameter divided by its focal length. It turns out that - in theory - any lens with the same f/stop will produce an image of the same brightness, and therefore requiring the same exposure. In practice, all lenses absorb or reflect a little light - they are less than 100% efficient. The T/stop of a lens is the actual measured effective f/stop.

Whereas f/stop is the correct number to use to find the depth of field of the lens, it is slightly inaccurate in calculating exposure (typically we are talking about a fraction of a stop, so don't sweat on the difference too much!). T/stop is the stop to use for exposure settings.

But DO look at the other references - there is already a wealth of information on this site and others, ready for the picking.
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