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Photography technique – Long exposures

In a recent post covering top tips for photographing waterfalls I referenced a technique known as long exposures. There is no clear cut definition on how long your shutter should remain open in order to be classed as a long exposure however I typically consider this as shots that last for one second or longer.

For waterfalls, long exposures are commonly used to smooth the surface of the water in order to create a beautiful, silky effect while the rest of the scene is sharp and in focus. However, this is only one of a number of applications for this technique. From capturing seascapes and landscapes to motion blur, light trails, star trails, the Milky Way or the Northern Lights, long exposures can turn average images into amazing images.

What’s more, this technique is easy to learn so read on to find out how.

First things first

Before I start it is important to quickly touch upon the basics of how most cameras work and how they interact with light. Light is essentially the fundamental principle of photography and impacts not just how the image looks but how it is captured. When you understand how to control it your images can make a dramatic improvement.

In very simple terms (as this varies slightly depending on the type of camera), light reflects off the subject you are photographing and enters the camera’s lens. It bounces off the mirror and prism into the viewfinder you are looking through. When the shutter is pressed, the mirror lifts so that the light is directed onto the camera’s sensor and the image is recorded.

Pre-shutter press

Pre Shutter press. Photo: Ilford Photo

On Shutter press

On Shutter press. Photo: Ilford Photo

How that image appears is dependent on just how much light there is. For this tutorial I’ll use the example of capturing cityscapes in low light.

Cityscape in low light

Cityscape in low light

The 3 pillars of photography

If you have ever tried to shoot in a city at night your images may appear very dark with little or no detail. They may also be blurry or full of an unpleasant speckled effect known as ‘noise’.

These things occur because the camera is trying to compensate for the lack of available light the best way it knows. The amount of light let into the camera can be controlled by several factors – all of which you can manage yourself to achieve better shots. These are the “3 pillars of photography” and are common terms you will encounter:

ISO Shutter Aperture Photo: Imgur.com

ISO Shutter Aperture. Photo: Imgur.com

  1. Aperture – the hole in the lens that controls how much light is let in. This is measured in f numbers or stops which you will see written as f/2.8, f/8, f/20 and so on. You may notice these written on your lens for example. The thing to remember is the smaller the f/ number, the wider the aperture. In other words to let more light in you need a bigger hole so you choose a smaller number. f/2.8 = big hole = more light while f/22 = small hole = less light.
  2. Shutter Speed – this controls how long the shutter remains open. The longer it stays open the more light is let in – hence the term ‘long exposures’. This is measured in seconds or fractions of a second.
  3. ISO – ISO is the level of sensitivity to available light. The lower the ISO the less sensitive it is, the higher the ISO the more sensitive it is. Each digital camera will have a base ISO, usually 100 or 200 and this can expand to well over 25,600 on many modern cameras (although these images aren’t always great). The quality of the camera’s sensor will determine how the image is recorded with the base ISO typically recording clean images while at higher ISOs you increase the risk of image noise.

Available light

Cityscape after sunset

Cityscape after sunset

So with a basic awareness of those 3 pillars we turn our attention to ‘available light’. In other words, the amount of light (either artificial or natural) entering your camera. Depending on the effect you are trying to achieve, along with available light, will determine how the above elements are used.

Using our cityscape example again. After sunset, and once the sun has dipped far enough below the horizon, the sky starts to take on a blue hue. This gets deeper and darker the further the sun sinks below the horizon. This is often referred to as the ‘blue hour’ (the period of twilight after sunset). Often street, vehicle and building lights will come on in cities (or become more noticeable). This is the perfect time to shoot long exposures to get the cleanest images.

This is because as available light decreases you need to compensate for this in the camera. One option is to widen your aperture but for cityscapes you ideally want to use a narrow aperture to keep as much of the scene in focus. You can also increase your ISO but in doing so you will add more noise to the image. This effectively leaves exposure time. A longer shutter speed will let more light into your camera while maintaining clean images (providing your camera is stable).

What you need to do

For long exposures it is essential to stabilise the camera (ideally on a tripod) in order to avoid any movement and then use a combination of all three variables (ISO, aperture and shutter speed) to achieve the optimum image quality.

A good way to get started is to fix the lowest native ISO (typically 100), select a narrow aperture (somewhere between f/11 and f/16) and then adjust the exposure based on the scene, the available light and what you are trying to achieve from the shot. This could range from a few seconds to a few minutes.

All the variables can be tweaked or adjusted to get your desired output. For example, as natural light decreases, or if you find the length of the exposure to be unpractical, simply increase the ISO slightly or widen the aperture. Both of which can reduce the length of exposure needed to let in a similar amount of light.

Now compare your long exposure to a handheld shot of the same scene. Not only is your long exposure sharper with better focus, it should have a lot less noise and be better exposed across the whole scene. With less available light the benefits and differences become even more pronounced.

Note: If it is daytime, for example shooting waterfalls, landscapes or seascapes, then a long exposure can blow out part or your entire image making it too bright and losing the detail in the highlights. You can combat this using an ND filter which is a dark piece of glass you place over the end of your lens reducing the amount of light that enters.

Equipment

With the above things in mind it is now time to take control of your camera and try some long exposures yourself. There are a few things you will need to get started.

  1. Camera – You will need a camera that gives you manual functions to control ISO, aperture and shutter speed. All DSLRs, CSCs and most bridge cameras will have this capability as well as a lot of compact cameras and even some phone cameras.
  2. Tripod – The most important accessory you will need is a tripod. Your camera must be kept perfectly still while the shutter is open or the image will be blurred. While you can rest your camera on a wall or other stable object, a tripod will offer considerably more flexibility when composing your shot. The process of using a tripod also makes you slow down and think carefully about the image you are creating, both compositionally and technically.
  3. Remote Shutter Release – These are not essential however a simple remote shutter release will remove the risk of camera movement caused by pressing the camera’s shutter. They also give you better control over the timing of shots in Bulb mode.

10 simple steps to capture stunning low light cityscapes using long exposures

  1. Use a tripod
    Avoids any camera movement that can cause blur and allows you to do long exposures.
  2. Shoot raw
    If possible set your camera to shoot raw. This way you can then improve noise, exposure, shadows and highlights and more in applications such as Adobe Lightroom.
  3. Set a low ISO
    Keeps your image as clean as possible and sets the level on which to base your exposure time and aperture.
  4. Shoot in Manual or Bulb* mode
    Allows you and not the camera to dictate the image parameters. *Use Bulb mode if you are shooting light trails or need an exposure time over 30 seconds.
  5. Use Live View
    Auto focus can struggle in low light so if necessary manually focus (using the live view magnifier or focus peaking).
  6. Switch lens to Manual
    Fix your focus then switch to Manual on the lens to lock this focal point. This avoids the camera hunting for Auto focus once you click the shutter.
  7. Turn off any lens Image Stabilisation
    Lens based stabilisation is not needed and can cause minor degradation of the image when the camera is on a tripod.
  8. Mirror Lock Up
    In DSLRs use the Mirror Lock Up function to avoid the minor vibration that they can cause when the image is taken.
    Camera 2
  9. Remote shutter
    Use a remote release to avoid any camera shake caused by pressing the shutter. Great for Bulb mode shooting too.
  10. Setting aperture and exposure
    Start with a narrow aperture (between f/11 to f/16) and adjust the exposure time depending on the amount of available light (both natural and artificial) and what you are shooting.

 

All images copyright Matt Parry unless otherwise indicated.

We would love to see these tips put into practice! Don’t forget to enter your images into our monthly Moment of the Month competition.