Shooting Long Exposures: Tips For Revealing The Invisible In Your Images

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Time is that elusive element that we all chase every day; that element we never seem to have enough of. That element we cannot see, but which rules our lives. Imagine we could see it - or rather the cumulative passage of it. Well...we can do this by using a camera, and very long exposures. By using long exposures, anything from half a second, to several minutes, or even hours - we can show what happens in our world over time.

Imagine

Obviously, you need to find a scene that lends itself to this type of photograph. Then you need to see, in your mind’s eye, what you hope the end product will be. Such an image will work best with a combination of still and moving subjects, so think of scenes such as the night sky moving around a fixed point on Earth, clouds drifting above you, water flowing in a stream or traffic gliding along a freeway. These are some of the classic long exposure shots.

Set up your camera

Compose the image in your viewfinder, and make sure your tripod is standing on a firm and stable surface with the legs extended, the center column retracted and the strap put away so it does not catch the wind. The last thing you need is for your camera to wobble while undertaking a long exposure, as that will create blur or ruin the photo completely.

This type of photograph works best with a deep depth of field, so look at using f/stops from f/11 to f/22. Check your exposure using a meter.

Neutral Density Filters

Neutral Density Filters are just that; they are filters that block out light while not interfering with the color of the image. Another way of looking at them is to think of them as sunglasses for your camera. 

ND filters come in several types. Fixed ND filters are rated according to a specific number of density stops. Variable ND filters will rotate and allow an increased or decreased level of density. Graduated, or split, ND filters is where the density is set over half of the filter, while the other half is clear.

Variable ND filters are best for newcomers to this type of photography, as they allow you to vary the degree of density without having to carry many different filters. Also, you can manage the density should weather conditions change during your exposure.

These filters are graded in ‘stops’, and each stop will reduce the amount of light passing through the aperture by a factor of 2. For example, ND2 or 1 stop reduces the light by 2, ND8 or 3 stops (2 X 2 X 2 each stops reduces by a factor of 2) will reduce the quantity of light by 8. The largest factor is 10-stops, which reduces the light by a factor of 1024, meaning your shutter needs to stay open over 1000 times longer than normal.

These filters are the reason you get the brushed effect of water running in a stream, or the soft drape of clouds moving across the sky. The downside is that you need to ensure that your camera is stable, and you calculate your workflow correctly. It will take some practice in using these to get your desired effect.

Focus

With the density of the filter, you may well find your autofocus will not function properly unless the conditions are incredibly bright. For best results, make sure you compose your shot precisely and allow the camera to focus before fitting the filter. Switch your setting to manual focus and very carefully attach the filter. Your camera will not hunt for a focus when you open the shutter.

Calculate your exposure time

The math around this is quite simple. For example, if you would expose this shot (without the ND filter) at 0.25 seconds and you are using a 4-stop ND filter, you need 0.25 seconds X 16 = 4 seconds. If you completed this same exposure with a 10-stop filter, then your calculation would be 0.25 (original exposure) X 1000 = 250 seconds, or 4 minutes. An exposure without the filter is ¼ s, when using a 10-stop filter it becomes 0.25 s x ~1000 = 250 s, 250 s / 60 = ~4 minutes. 

Assuming the light will remain constant, this technique is fine. In shifting light conditions, an app can be a handy tool to have. Look for NDTimer on iPhone, or NDCalc for Android. They will save you time and frustration in trying to get the lighting right.

Shoot as a RAW image

If your ND filter tends to leave a slight color cast on your image, try shooting as a RAW image and use post-processing to try and correct the cast. One way to prevent this slight color cast is to fit your viewfinder cap before starting your exposure. By doing it this way, you will prevent any stray light from entering and spoiling your image.

ISO

Take your ISO setting off auto, and set it to the lowest setting you have on your camera. For bright daylight, this should be around 100. Part of your testing will be to determine the correct ISO settings for your location and conditions. If you are getting dark images, then notch this up a little to compensate. Over time, you will become familiar with what ISO is needed and when.

Last settings

One of the last things you should look at using is the “BULB” setting on the camera if you intend to expose for longer than 60 seconds. Using this does mean you should use a remote shutter release cable. This ensures you can lock the shutter open for your calculated amount of time. Also, it is impossible to keep your finger on the button for this long and not have it affect your image. A timer on your phone will help to count down and notify you when the time is up. Lastly, if your camera has a mirror lock function, use it. Locking the mirror out of the way before capturing the image will negate any tiny amount of movement that can cause a blur on a carefully arranged image.

Things you cannot control

Even with the best planning, things are bound to go wrong at some stage. Sometimes the wind dies down or the clouds part, and your image does not turn out as you were hoping. These things happen to the most experienced of photographers and are not a reason to give up on this form of art. Photographs such as these are the best blend of art and design, and allow the photographer to explore a different type of their craft, one that relies on your imagination to try and foresee what an image will look like after a few minutes exposure.

You do not have to travel far to find inspirational elements to photograph. They do not rely on exotic locations. Clouds, water, and stars are available to just about everybody in the world, and those images of velvet water or softly draped clouds will bring you immense pleasure.

Challenge yourself to discard the idea that photography must freeze the action. Rather, take the time to capture the moving action in an inspired and compelling manner. Mastering this form of photography will bring you overwhelming satisfaction, and pleasure to your audience as well.

Have you tried long exposures with your camera? We would love to hear your experiences and tips. Leave us a comment to share your thoughts!

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Gönderildi 8 Ağustos, 2017

TomCoulter

Designer // Writer // Creative

Tom is a Design Correspondent for Freelancer.com. He is currently based in Melbourne and spends most of his non-work moments trying to find the best coffee.

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