Being able to shoot what’s known as ‘long exposure’ in essence is learning how to change and control your shutter speed. But what is Shutter Speed. Basically it’s the amount of time the camera’s shutter is open and is measured in seconds or fractions of seconds. A fast shutter speed like 1/1000 will freeze anything the camera captures while a long shutter speed 10 seconds captures anything that moves while your shutter is open. That’s why the water looks like silk and cars leave light trails in certain images.
For Long Exposure Photography a tripod is essential. Dealing with shutter speeds of many seconds, or even minutes, it’s simply impossible to take pictures handheld and get a sharp image. Always use a tripod when dealing with shutter speeds longer than 1\60 sec.
2. Shutter Release
Using a remote ensures that the camera stands still on your tripod and does not move. (Alternatively, you can use the self-timer function on your camera.)
You’re able to get a shutter speed longer than 30 seconds by using Bulb Mode in your camera.
Releases come in two forms; one that connects to your camera via a cable, and the other via infrared.
3. ND Filters/GND Filters
An ND Filters job is to limit the light coming into the lens and lets you shoot with extremely slow shutter speeds even in bright light.
These come in different sizes, namely 2 Stop, 6 Stop and 10 Stop.
The numbers are the different strengths of the filter.
Each ‘stop’ of an ND filter reduces the amount of light entering the camera by a factor of 2.
A fairly common 2-stop filter (ND4) reduces the amount of light hitting the sensor by a factor of 4. A 3-stop (ND8) filter by a factor of 8 and so on. A 10-stop filter reduces the light by a factor of 1024, meaning that the shutter needs to be open for over 1000x longer.
Cameras cannot expose the detail of extremely low light and dark scenes at the same time. That’s where Graduated Neutral Density filters come in. The reason you will want to use an ND grad filter is that there can be a substantial difference, light wise, between the sky and your foreground.
Setting up the shot – Compose and focus
The first thing that you should do is to set your focus point. Do this before you put a filter on. Switch to manual and focus about a third into the scene. Don’t switch to Auto!
Keep your ISO on 100, use an aperture between f8-f11 for a good depth of field.
There’s one more step left before you can begin using the filter: take a test shot. By taking a test image you ensure that the photo is sharp and you know what shutter speed is ideal without a filter. You want to remember this number as it will be important when we calculate the shutter speed with the filter.
Time to take the shot
Set Exposure with the filter
It’s time to add you filter! When just using a GND you should be able to adjust the shutter speed and see the exposure in live view.
When using a 10 stop filter, or a filter dark enough to require a shutter speed of more than 30 seconds, set your shutter speed to “Bulb”. Bulb mode keeps the shutter open as long as the trigger is pressed. This is why you want a shutter release.
At this point, you might begin to wonder how you’re supposed to calculate the shutter speed when the filter lets through less light.
Well you can either do the maths or use an App that helps you calculate your exposure time! There are plenty of good ones in the App stores. Eventually though, with practice, you should be able calculate the time from experience.
Remember to act fast because the scene and light changes quickly!