Yesterday I received my B+W 10 stop ND filter, which as you can guess, reduces the amount of light getting to the sensor by 10 stops, making it perfect for taking long exposure shots in pretty much any light! Handy!
The weather wasn’t terribly nice last night at Wick’s South Head, but that made for a nice big swell in the sea, and the white, frothy water being thrown up onto the flat sedimentary rock produced the following shot:
I took this shot at ISO 100 – f/8 for 30 seconds, the base exposure (metering the shot without the 10 stop filter attached) was 1/30th of a second.
Let me explain the procedure I used to take this in steps:
The only complicated thing is calculating the new shutter speed, but even that’s not too difficult.
If you like mathematics, the formula for calculating shutter speed with a neutral density filter is quite simple:
T(n) = t x 2 ^ n
n = Stop value of your ND filter (10 stops for my ND filter)
t = Base shutter speed (without filter attached) in seconds (1/30th of a second for my shot)
T(n) = Final exposure time
So, for the above shot we calculate:
So, about 34 seconds (Yep, I slightly underexposed my shot).
If you’re not very keen on doing the above calculation every time you want to take a long exposure shot there are smartphone apps available to do it for you. The one I use on my iPhone is called LongTime Exposure Calculator, and it’s free!
There is also a free app for Android smartphones called Exposure Calculator, and although I’ve never used it, it looks like a good one.
Just because long exposures of moving water and sky are cool, don’t forget that moving water and sky also look pretty cool when they are frozen with fast shutter speeds:
So, take both types of shot when the opportunity arises!
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© All text and images copyright 2013 Gordon Mackay. All Rights Reserved.