25.06.2015

LONG EXPOSURES WITH NEUTRAL DENSITY FILTERS

25.06.2015

LONG EXPOSURES WITH NEUTRAL DENSITY FILTERS

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If I have to recommend a satisfying technique to a beginner photographer that will enable him or her to obtain good results right from the start, with images that are a pleasure to look at and to show, then I can only suggest long exposure.

WHAT IS IT?

Very simply, it involves exposures with a long (or slow) shutter speed, such that create a series of very unusual and interesting effects that we are not used to seeing with the naked eye. A “long exposure” is any photo with a shutter speed of 5-6 seconds or more.

WHAT METHODS CAN YOU USE?

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There are basically two methods for obtaining long exposures:

  1. taking photos in the evening, when the light is low and you can use long (or short) shutter speeds without difficulty;
  2. taking photos is the full light of day using a neutral density filter, which serves to obscure the light (the equivalent to putting sunglasses on your camera lens).

Obviously, in full daylight it is impossible to use a slow shutter speed without a neutral density filter, due to the light intensity.

WHAT DO YOU NEED?

With neutral density filters or without, you don’t need expensive or specialist photography equipment to take long exposure images. You need:

– a camera with manual or semi-automatic controls (Shutter/Aperture Priority);
– a good tripod (I recommend the Befree series, 190 or 055 by Manfrotto);
– a neutral density filter for long exposure shots taken in full daylight (optional).

THE IDEAL CHOICE OF SUBJECT

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Taking photos using the long exposure technique is very satisfying; however, the ideal subject must be chosen with care. It is not enough to take random pictures; there are some things that work well with this technique, and others less so. Here are some tips:

Waterfalls and rivers

These two elements are characterised by fast running or falling water. They are ideal subjects for trying out long exposures with neutral density filters. The movement of the water, captured with a long (or slow) shutter speed, allows you to obtain a very characteristic and striking veiled effect. Furthermore, as they are generally found in woodland or between wooded valleys, the light conditions are such as to enable you to take long exposure shots even without the use of a neutral density filter in full daylight.

Rough seas

Another ideal subject for this type of photography is a rough sea. As with waterfalls and rivers, the unpredictable and undulated movement of the water, captured using a long (or slow) shutter speed, gives you interesting and unique images with the sea taking on a visual effect similar to that of velvet. In these conditions too, in which the weather usually involves a cloudy or stormy sky, the low light conditions allow you to use long (or slow) shutter speeds in full daylight even without the use of neutral density filters.

After sundown

This third option is closely connected to the absence of light. As soon as the sun goes down, the light begins to fade progressively and this allows you to use long (or slow) shutter speeds without the need for filters. In this context, you can photograph practically anything; however, it makes non sense to take long exposure pictures of static objects. If you decide to take evening photos, you have to find scenes with elements in motion, such as an arterial road or a funfair. In these conditions, you will have every opportunity to take simple, long exposure pictures without the use of filters.

GUIDELINES

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Once you have outlined your subject, all that remains is to roll up your sleeves and get to work. Here are various things I recommend you do for using this photography technique:

  1. Set up your camera on the tripod and compose your scene according to your personal taste;
  2. Set your camera to APERTURE PRIORITY mode (indicated by the abbreviations Av or A, depending on the model). This gives you control over the aperture size (which regulates how much light reaches the sensor);
  3. Set the aperture at a value of f/16;
  4. Set the camera’s ISO level to the lowest value possible (usually ISO 100, but it could be 50 or 200, based on the model);

ANALYSIS

At this point, if there’s not too much light, the camera should suggest a long (or slow) shutter speed, with a value of 4-5 seconds or more. Indeed, using Aperture Priority, the camera will determine the ideal shutter speed on its own.

If the conditions suit the settings, then you can take the shot certain to obtain a long exposure photograph. In this case, I recommend using a remote shutter release cable or the self timer (the function that allows you to delay the shot by 2 or 10 seconds, which is usually used for self-portraits), in order to avoid any vibrations caused by touching the camera.

If the conditions do NOT suit the settings, that is to say the shutter speed is too fast, then it means there is too much light. To solve this problem, you can try one of the following:

– close the aperture by setting it to a value of f/22, with the risk of ending up with an unclear image;
– use a neutral density filter to reduce the amount of light that reaches the sensor;

WHICH NEUTRAL DENSITY FILTER?

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The filter you need for this type of photography is called an ND FILTER (Neutral Density).

There are a huge number on the market, with lots of different abbreviations and values used to indicate “how dark” they are. Obviously, the darker they are, the less light they let through.

Which should I choose from? I usually recommend the 10 STOP filter, the darkest of those easily found in the various online shops. This means that you have a much more versatile filter that allows you to obtain better results in many more situations.

The 10 STOP neutral density filter is identified by one of the following abbreviations:

– ND 3.0 FILTER
– ND 1000 FILTER

Both of these abbreviations (ND 3.0 or ND 1000) are used to identify the same type of filter; using one rather than the other is merely the choice of the producer.

Graduated neutral density filters are not the same and have other uses; don’t bother with them at all.

COMMON PROBLEMS AND HOW TO RESOLVE THEM

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As long as you don’t use neutral density filters, you won’t have any problems; if the shutter speed is too slow (or long), all you have to do is widen the aperture a bit, taking it to f/8 or f/5.6 to normalise everything, or increase the ISO value to 200 or 400.

However, when you use neutral density filters, you might come up against a few little problems. In certain cases, using neutral density filters causes problems with the camera’s autofocus, so you have to adjust the manual focus BEFORE placing the filter in front of the lens. In other cases, what could happen is that the camera, with such a dark filter, tends to use excessively slow shutter speeds (30 seconds or more). In such cases, do the same as suggested above: widen the aperture (f/8 or f/5.6) or increase the ISO value (200 or 400).

If the images, seen on the computer screen, appear blurry, it means that the camera isn’t stable during the shot (which can last for several seconds). In this case, make sure you didn’t touch the camera by mistake, that there is no strong wind that makes the camera or tripod shake, and that you are using a suitable tripod.

CONCLUSION

Long exposures, as you can see in the examples in this post, are very interesting and enable even the least experienced photographer to obtain striking results.

A long exposure is usually effective with shutter speeds of 4-5 seconds and 20-30 seconds. There is nothing to stop you taking photos with even slower shutter speeds (above 30 seconds you are forced to use Bulb -B- mode) but, for this type of photograph, you need to have a bit of knowledge and experience to best manage the scene.

Alessio Furlan

Freelance photographer, photography teacher, author and blogger.

website: www.alessiofurlan.com
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