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Re: Shutter Speed

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Leo Ticheli
Re: Shutter Speed
on Sep 22, 2002 at 10:14:34 pm

Jeff, Jeff, Jeff...

This is very basic stuff, hang on...

Your exposure is affected by the aperture (also referred to as the iris and f-stop or t-stop) and the duration of the shutter which is a function of the frame-rate and the shutter speed. The longer the shutter is open, the more light reaches the chip/film.

First the aperture. The bigger the hole in the lens, the more light goes through in a given amount of time. The larger the f number the smaller the hole (f3.5 lets in more light than f5.6). We use a large aperture to reduce depth of field and a small aperture to increase it.

Now the duration of the shutter. Some cameras have no separate shutter, so they are always 1/30 of a second (NTSC cameras). Cameras which have a separate shutter can reduce the duration of the shutter, but, of course, never make it longer than 1/30 of a second.

A camera with variable frame-rates can have the shutter open longer than 1/30 of a second by shooting at a slower frame rate. For example, the Panasonic Varicam HD camera can shoot as slow as 1/4 of a second when the 4 fps rate is selected.

May I suggest you locate a Cinematographer near you and ask them to explain these concepts to you and under which circumstances they are employed. It's much easier in person than in a brief post. Even a still photographer should understand these concepts.

I hope this helps.

Best regards,

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