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Old May 22nd, 2009, 08:16 PM   #1
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Join Date: Feb 2003
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How much ND to get Live Mode under control?

I have the Casio EX-F1 which -- like most other cameras -- offers almost no control when shooting video.

I've found that with a 6-stop reduction in light (two 3X ND filters) the shutter-speed in bright EV15-EV16 light can be forced to 1/50th which is correct for shooting p30.

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Even if your camera can set shutter-speed and gain -- unless the camera has built-in auto ND filters like a camcorder, you'll still need to add ND filters to keep the aperture to f4 to f5.6. Does the GH1 have these?

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Getting there was not EZ!

At Wide, the aperture is f2.7 and as it moves toward Tele the maximum decreases to about f4.6. So at Wide, maximum light enters for 1/50th at an ISO of 100. As one zooms, the T-stop is reduced and naturally the shutter-speed goes up. At 100mm, it is 1/100th and ISO has doubled to 200. (This indicates 2-stops less light--which seems too much.)

This suggests that 7-stops may be a better option because 1 less stop of light might force the Tele from 1/100th to 1/50th. And, at Wide, gain would go from 100 to 200.

Less light can cause AE to decrease the shutter-speed OR it can increase gain. At Wide, gain must increase. At Tele, shutter-speed is likely to be decreased from 1/100th to 1/50th.

In any case, an ideal balance will only occur at a single EV value. A super bright EV17 day will likely push-up shutter-speed. A cloudy day (EV14 or EV15) will cause gain to be added at Wide and cause shutter-speed to fall.

I suspect a circular polarizer plus a regular polarizer to adjust the light may be the ultimate, but very expensive, solution.

PS: Since I can shoot still pix while recording video I can check the Live View/Movie Program AE operation. The AE photo program is very different.
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Last edited by Steve Mullen; May 23rd, 2009 at 05:09 AM.
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Old May 24th, 2009, 01:25 PM   #2
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Join Date: Jan 2009
Location: Valencia Spain
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Thank you very much for share your research, it's very valuable info for us EX-F1 users ;)

A question:
I have a circular polarized, so... you think is better to buy (add) a regular polarized to decrease the shutter speed or should I buy two ND3 filters?
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