HDR is an increasingly familiar term in photography. We've all…
I’ve had a few questions about how I took this photograph of Trwyn Du lighthouse on Anglesey. The technique is simple: long exposure using a neutral density (ND) filter. This tutorial will explain how to do it.
This post is split into six sections:
- The theory
- Get your kit together
- Choose a time and location
- Set your kit up
- Take the shot
I’ll take you through the steps one by one…
1. The theory
The unique characteristic of this photograph is the motion effect in the water and the clouds. You get this by taking a long exposure – anything from a few seconds to several minutes. In a normal photograph with a shutter speed of a fraction of a second, everything is frozen in position at the exact moment you release the shutter. With a long exposure, the photograph shows the position of the water and clouds (and anything else that moves) over a much longer period, which gives you a blurred effect and the impression of motion.
For this tutorial, we’re going to concentrate on the effect shown in this photograph. But the same process can be used in other situations. I used a one second exposure to show the motion of people in this shot, and with a much longer exposure you can even remove people from street scenes entirely. It’s a very simple yet powerful technique – give it a try and see.
Before we proceed, a brief recap of the exposure triangle. To take a properly-exposed photograph, the right amount of light needs to reach the sensor. Too little, and the image will look too dark (under-exposed). Too much, and it will look washed out (over-exposed). Achieving this requires the correct combination of aperture, shutter speed and ISO, together known as the Exposure Value (EV). You can read more about the exposure triangle on fstoppers.
A change in EV of double or half is referred to as a ‘stop’. Going from ISO 100 to ISO 200 doubles the sensor sensitivity, meaning an increase in EV of a stop. Changing the shutter speed from 1/100 second to 1/200 second will halve the time the shutter is open, halving the amount of light reaching the sensor, and so decreasing EV by a stop. If you make both those changes together, the overall EV will stay the same – one compensates for the other.
Back to the photograph. For this image, I used a shutter speed of 30 seconds – far longer than normal. As we discussed above, this means much more light reaches the sensor. Compared to a typical shutter speed of 1/30 seconds, 900 times more light will reach the sensor, equivalent to just under 10 stops of EV. (If you’re still working that out… if you double 1/30 ten times, you get 1024/30, or around 34 seconds – a little more than the exposure I used.)
To compensate for this, you need to reduce the EV by around 10 stops in another way. However, reducing ISO or aperture by 10 stops will not be possible on the average camera and lens – it’s too extreme. You therefore need another way to reduce the exposure – and this is where an ND filter comes in.
An ND filter is essentially a dark piece of glass that reduces the amount of light that gets through to the camera. For this shot, I’ve used a 10-stop ND filter which roughly matches the numbers above. The ND filter compensates for the long exposure, and you can then fine tune with small aperture and ISO adjustments as you normally would.
That’s the theory over with… now for the action!
2. Get your kit together
This is the equipment I used:
- Canon 7D camera body with Canon 17-55mm lens
- Giottos YTL 8354 tripod with Giottos MH5011 tripod head
- B+W 10-stop ND Filter
- Remote shutter release
- Adobe Lightroom CC for post-processing
But really, the main requirements for daylight long exposure photography are a camera that allows you to set the shutter speed manually, a tripod and an ND filter (ideally 10-stop) that all attach together. The tripod needs to hold the camera absolutely still for the full exposure, so choose carefully. The remote shutter release is to avoid camera shake as you press the button – but you could set up a two second delay (if your camera has that function) and use the normal shutter release button instead.
3. Chose a time and location
The long exposure photograph above is of Trwyn Du Lighthouse at Penmon Point in Anglesey in the UK. The rocky shore, the striking lighthouse and the sweeping sky make for a great long exposure. But most scenes with water or clouds will show a cool effect.
With water, there will almost always be movement which will give you interesting results with long exposures. With the sky, it’s worth experimenting with different levels of cloud – if there’s too little or too much, you won’t notice the effect.
As for the time of day, the standard considerations apply. I took this photograph in the early evening, shortly before sunset, which helped achieve the warmth in the image.
4. Set your kit up
I won’t go into general composition rules as that’s beyond the scope of this tutorial. The key requirement for a long exposure is keeping the camera rock steady. Any movement whatsoever will result in the whole image being blurred, so a decent tripod is key. Here I set my tripod up in a wide stance to adequately brace the camera on the rocks, I wrapped the camera strap around the tripod to avoid it being caught by the wind, and I attached some weight to the tripod to keep it steady. (I also kept a watchful eye on the incoming tide to prevent getting cut off!)
5. Take the shot
How you compose the shot will depend on the type of camera you have. Trial and error is key: experiment with shutter speeds from a few seconds to a few minutes, if conditions allow. The longer the exposure, the stronger the motion effect. I took around 30 different shots before I got the image I wanted.
Most cameras allow you to set a shutter speed of up to 30 seconds. If you need a longer exposure, or you need one that doesn’t match the options available in your camera, see if there is a ‘bulb’ mode. This allows you to control precisely the exposure length – the shutter opens when you press the button, and closes when you release it. It helps to have a timer to hand if your camera doesn’t display the elapsed time.
I always shoot in raw format because it’s more forgiving and allows you to regain more detail in post-processing if you don’t get the settings quite right. And remember that once you release the shutter the camera needs to stay perfectly still for the duration of the exposure.
(If your DSLR has a Live View mode, you can opt to enable that and follow the mirrorless instructions below instead.)
You’ll likely not be able to see much in the viewfinder once the ND filter is in place – it will be too dark. So instead, take a photograph without the filter on at a normal shutter speed – you can do this on the fully automatic setting if you want to. Once you’re happy with the exposure, make a note of the settings. Then, without changing the camera position or the focal length or focus of the lens, change the camera to manual mode and manual focus and put the ND filter on. Now keep all the settings the same, but increase the shutter speed by the number of stops equivalent to your ND filter. There are lots of free calculator apps that will work this out for you, but if you’re using a 10-stop ND filter, multiply your shutter speed by 1024. (If you don’t have a calculator, 1000 will do.)
You often won’t be able to select the exact shutter speed you calculate. In the example above, 1/30 times 1024 is 34.1 seconds. The closest shutter speed setting available is probably 30 seconds (which is what I used) – so try this and see how it comes out or use ‘bulb’ mode and time the exposure exactly. But it doesn’t have to be exact – there’s always an element of trial and error. When you’ve reviewed the first shot, make adjustments to shutter speed, aperture and ISO in the normal way until you get the result you’re looking for. You can always fine-tune the exposure in post-processing.
With a mirrorless camera (or a DSLR on Live View mode), it’s a lot easier: you can compose and focus the shot in the normal way using the electronic viewfinder or the LCD screen. Put the camera onto shutter priority mode, choose the shutter speed you want (e.g. 30 seconds) and the camera will do the rest. (If for some reason this doesn’t work, you can follow the DSLR instructions above.)
This is the long exposure image I got straight out of the camera (it’s actually a jpeg exported in Lightroom from the unedited raw file, with the default amount of sharpening applied):
It’s not a bad photo, but it’s a little underexposed and flat looking. I also think the position of the lighthouse isn’t ideal – the image doesn’t feel balanced.
I decided to crop it to make a portrait image with a greater focus on the lighthouse. Then I applied the settings below in Lightroom CC’s develop module to lighten the image, add some contrast and vibrance, and bring out the light catching on the rocks. I also added a small amount of vignetting to draw the viewer’s eye into the centre of the image.
And that gives us the final long exposure photograph…
I hope you found this tutorial useful. It’s the first one I’ve published, so I’d love to hear what you think. And if you have any of your own tips and tricks, please share them in the comments below.