>I don't recall the exact number but I think he ended up with a daylight
>exposure of about 45 seconds. I understand the use of the variable ND
>filter to reduce the brightness of the sky but I don't understand the
>use of a 10 stop ND filter. Clearly the 10 stop ND filter is
>responsible for the very long shutter speed but why so long. It seemed
>to me that the clouds were moving fairly briskly and that such a long
>shutter speed wouldn't be required to simply blur the clouds.
>It there some other reason for using that 10 stop ND filter that I don't
It's very likely that the photographer wanted precise control over the ND
filtering, and at the 10-stop position of the variable ND filter fine
adjustment can be very difficult. By using the ND10 filter first he has
bracketed the lower end of the range he's interested in and then has fine
control over his desired setting.
When the going gets weird, the weird turn pro
- Hunter S. Thompson
Themed Olympus Photo Exhibition: http://www.tope.nl/