Tuesday, August 21, 2012

GBTimelapse - How To Calibrate a 9-Stop ND Filter

Simplify ND filters by using only one

Lately I've been using a single 9-stop filter to capture time-lapse during sunsets. By using a single 9-stop, I only need to make one filter change while the sun is setting. Previously, I used a stack of three 3-stop filters. But the filter stack added to vignetting, and using just one is much simpler.

The easy way to calibrate your ND filter

When using GBTimelapse AutoRamp in bulb mode with neutral density filters, it's best to know the exact value of each filter. Even though a filter may be rated at 9 stops, it may not be exactly 9 stops.
I have found filters that are more than ten percent different from their rating.

To avoid a change in image brightness when adding or removing a filter, AutoRamp needs to know the exact number of stops of the filter. There's an easy way to calibrate a filter using AutoRamp itself. This video shows you how:

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