How much ND to get Live Mode under control? at

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HD from Nikon D90, other still photo cams (except EOS 5D Mk. II, LUMIX GH1).

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Old May 22nd, 2009, 07:16 PM   #1
HDV Cinema
Join Date: Feb 2003
Location: Las Vegas
Posts: 4,003
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.


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?


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 04:09 AM.
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Old May 24th, 2009, 12:25 PM   #2
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Join Date: Jan 2009
Location: Valencia Spain
Posts: 8
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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