5 Things You Should know about Long Exposure Photography

Long exposure photography is extremely popular, yet also one of the photography techniques people find most challenging. I wanted to discus the things you should know about long exposures to help you get great results every time. I like to venture out at dusk or dawn to shoot long exposures, and I simply love the effect you get in the images. I get often asked how I do them, so I hope these tips will be of use to you.

5 Things You should know about Long Exposure Photography

1. How Long Should the Exposure be? 

Long exposures are usually shots that are taken with exposure times equal to or longer than a second. At this point, provided it is activated, a camera’s long exposure noise reduction system usually cuts in. Most cameras allow you to set exposures up to 30 seconds in length, but if you need an exposure longer than this you’ll have to switch to Bulb or Time mode. In Bulb mode the camera’s shutter opens when the shutter release is pressed (as normal) and it stays open for as long as the button is held down. In most cases this would be done using a remote release. In Time mode the shutter opens with a press of the release, but the button doesn’t need to be held down and the shutter is closed with a second press of the release. Bulb and Time mode can usually be used to make exposures of up to 30 minutes. Your camera’s manual will explain the maximum duration possible.

2. Long Exposure and Noise Reduction

Even though you may use a low sensitivity setting, long exposure images often suffer from noise. This noise is the result of inconsistencies in the sensitivity of individual pixels and the occasional ‘hot pixel’ and it therefore has a regular pattern that is specific to a particular camera. A camera’s long exposure noise reduction system works by capturing and analysing a ‘dark-frame’ which has the same noise pattern as photographic image and then extracting the interference from image. In order for this to work well the exposure of the dark frame has to have the same duration as the photographic image and when the long exposure noise reduction system is activated, it is captured automatically immediately after the ‘normal’ shot. This means that every image takes twice as long to create when the long exposure noise reduction system is used, but it’s worth it because the results are usually very good.

3. Essential tools for Long Exposure Photography

A remote release is essential for shooting long exposures because it allows you to open and close the shutter without touching the camera and making it wobble on the tripod (a tripod is also a must). Any wobble, especially at the start of the exposure, could cause slight blurring or loss of sharpness in your image. Cable or wired releases tend to be more affordable than wireless releases, but there’s a chance that any movement of the cable, perhaps caused by vibration created by wind, could introduce some blurring. Wireless releases allow you to stand further away from your camera and you don’t have a physical connection between you and it.

4. Battery Life and moving objects

Long exposures drain battery power quickly, so makes sure you have a spare or two if you’re planning to take lots of shots. One other thing is that during the long exposure time some elements in the scene which appear still, also move. The moon is a great example, it may appear stationary in the night sky, but it moves and it will be rendered as a cylinder shape in images created with exposures longer than a few seconds.

5. Neutral Density Filter for Long Exposures

Neutral density (ND) filters are often used to enable long exposures to be taken in quite bright light. A one stop filter reduces the amount of light entering a lens by ½ and extends exposure by 2x so it is often referred to as an ND2. Each additional stop of filter strength further halves the amount of light and extends exposure by two times. Hence a two stop filter extends exposure by 4x and is known as an ND4. This continues as follows: 3 stops = ND8; 4 stops = ND16; 10 stops = ND1024

I hope these points could help you to shed some light on the subject and I also hope you'll have a go at it. If you have any other questions, let me know in the comments below.

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