How I took this shot?
So how do you get those clouds to streak across the sky you ask? Well it’s by using a 10 stop neutral density (ND) filter. It’s like sunglasses for your camera. What a ND filter does is it slows down your shutter speed, which is the amount the aperture stays open, giving time for the clouds to move across the sensor of your camera. There are several ND filters that offer different “stops” of light. 3, 6, 10, 15 stops are the most common ones out there. They also come in round, screw in, or square. The round ones screw into the thread on the end of your lens. The square filter requires a filter holder. He’s a tip, if you do buy the round filters, go with the largest diameter of the lens you have. Then buy step down rings for the other lenses. If you’re good with math it’ll be easy to figure out, but we are in the age of technology so there’s an app for that.
Figuring out the right exposure
When trying to calculate the correct exposure with a ND filter, you have to figure out what the “proper” exposure is without the ND filter first. In the case of the image used, I got a proper exposure of 1/400th of a second at a F/Stop of f10. So if I use a 10 stop filter I would get an exposure of 2.5 seconds. Now I’ll be honest here, as an artist, I went with a longer exposure to really get those clouds moving across the sensor creating movement. I used a 30 second exposure. That’s 5 stops longer then what the filter is for. But since the day was overcast and showers were forecasted, I knew I can get away with a 30 second exposure and not “blow” out, most of the image will be overexposed, my image.
A ND filter can also be used on smoothing water movement making it nice and silky. One other important thing; Prior to you putting on the ND Filter, make sure your subject is in focus then turn off the autofocus on your lens. This will prevent the lens from trying to focus through that dark piece of glass.
So go out there and play around with ND filters and long exposures and let’s see what you get. As a fellow photographer says “hey, pixels are free.”
Location: Broad Street/ Meeting Street Charleston SC 03/30/18
Subject: St. Michael Church
Camera: Canon 6D
Focal length: 28mm Tamron 28-75 f2.8
Exposure: 30 second time exposure
10 Stop ND (neutral density)