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Daytime long exposure photography

Tips & advice from photographer Stefan Lozinsky


Long exposure photography at night is not all that difficult. To achieve a similar effect (blurring motion) during the day is another matter.
Long exposure photography at night is not all that difficult. To achieve a similar effect (blurring motion) during the day is another matter.

This article was graciously contributed by Stefan Lozinsky, an accomplished photographer who resides in Vancouver, BC, Canada.

When someone thinks of a photograph, he or she typically envisions a single moment in time, often captured in a split second. Long exposure photography, however, captures many such single moments in sequence over several minutes or hours to achieve a look not possible with conventional hand-held shutter speeds. For example, we have all seen streams of vehicle lights in long exposure night-time street photographs. These photos are taken with any camera capable of manual exposure at slow shutter speeds, solidly supported (by a tripod usually) to avoid camera shake.

The slowest-possible shutter speed is governed by the smallest aperture of the lens, which usually results in an exposure of between 30 seconds to several minutes, depending on the camera, the amount of light falling on the scene and the ISO sensitivity you have set for your digital camera or the film speed of your conventional camera's film.

Clouds in a long exposure provide a look of action similar to the northern lights in an otherwise static scene.
Clouds in a long exposure provide a look of action similar to the northern lights in an otherwise static scene.

During the day, it is far too bright outdoors to achieve shutter speeds slow enough to severely blur motion. But, if you attach the right light-absorbing (neutral density) filters to your lens, long exposure is possible in bright daylight, and can result in stunning daytime photographs. Blurring motion is not the only objective, though, of daytime long exposure photography.

MAKING OBJECTS IN MOTION "DISAPPEAR" CAN BE ANOTHER OBJECTIVE

If a photographer wishes to capture architecture or scenery in a touristy or highly populated area without showing the presence of people in the image, this daytime long exposure technique can be successfully employed. When the people in the scene are more or less passing through, never stopping for more than a few moments in one spot, then a three-minute, ten-minute, half-hour or an hour-long exposure will result in only the static objects appearing in the final capture. It will look as if the people were not there at all.

BLURRING MOTION IS THE USUAL OBJECTIVE

Long exposures are generally used to blur motion, thus for the technique to be effective it's necessary that there is motion in the daylit scene you are photographing. Objects that move slowly are unlikely to be blurred when using a fast shutter speed. Slow down the shutter speed and their motion becomes apparent in the image. Think of clouds moving across the skyline. A very slow shutter speed will cause the clouds to look like streaks in the sky. Water moving on a pond becomes flat and void of any detail. The effect can be very impressive, producing unusually attractive pictures of scenes that we don't normally see that way.

To successfully achieve a daytime long exposure, three pieces of equipment are essential:

  • a camera with manual exposure capability,
  • a means of keeping the camera absolutely immobile during the long exposure, such as a good tripod, and
  • one or more neutral density filters
  • .

    THE ALL-IMPORTANT NEUTRAL DENSITY FILTER

    The purpose of a neutral density filter is to reduce the amount of light entering the lens without otherwise altering or affecting the image, allowing the photographer to drastically decrease the shutter speed and still achieve proper exposure.

    Neutral density filters are available in different strengths or grades, reducing the amount of light from 0.3 stops to 13 stops and even more. In order to obtain the slow shutter speeds described in explaining this technique, a 6-stop or a 10-stop filter works well for most daytime shooting situations. For images requiring an even slower shutter speed, you can choose a denser filter or stack the filters together. Typically, manufacturers create neutral density filters with threads on both front and back, permitting them to be snuggly screwed together on the front of the lens for any number of filter combinations.

    Neutral density filters are very dark. So dark in fact that, when placed in front of the lens, the camera's meter can't provide an accurate exposure of the scene. Actually, the camera can't even auto-focus properly.

    To remedy this, it's necessary to set up the camera on a tripod, minipod or some solid support to minimize camera shake, then to meter the scene and focus the camera (making sure to leave the focus on the lens set to manual and not automatic) before attaching the neutral density filter (making sure not to bump the focusing dial). Then, adjust the shutter speed dial to the BULB setting (provided that the required exposure is longer than your camera's maximum shutter speed setting. 30 seconds is my camera's maximum shutter speed, and maybe yours, too).

    NOTE
    Your camera's slowest shutter speed may be 15 seconds, 30 seconds or possibly even one minute depending on its make and model. And it may or may not have a B or "BULB" setting, which permits the shutter to remain open as long as the shutter button is depressed, and is essential to make a very long exposure.
    Also, many digital cameras that have a B setting may restrict the amount of time the shutter can remain open to a couple of minutes.
    Check your manual to find out about your camera's shutter capabilities.

    Since it is not possible to pre-set an exposure of longer than 30 seconds on my camera, I set the shutter speed to BULB mode and use a rather sophisticated shutter release that indicates a running timer on its LCD display. I simply wait for the timer to reach the desired exposure duration and then manually close the shutter by releasing the shutter release trigger. You don't really need such a timing device, although it's a nice accessory. You can simply use your watch to count off the exposure time.

    Here are example photographs, followed below by a calculation showing how I determine the correct slow shutter speed and aperture for proper exposure when using neutral density filtration for my daytime long exposure photography of the sky and its clouds:

    The image on the left shows a traditional view of clouds. The others are daytime long exposures, showing clouds as streaks. The black and white image deftly avoids the problem of color shift due to an excess of infrared light.
    The image on the left shows a traditional view of clouds. The others are daytime long exposures, showing clouds as streaks. The black and white image deftly avoids the problem of color shift due to an excess of infrared light.

    DETERMINING WHAT SHUTTER SPEED, APERTURE AND ND FILTRATION TO USE FOR PROPER EXPOSURE

    • After observing the speed with which the clouds are moving (fairly slowly), I estimate that in order to capture their motion as streaks in the sky, I will need an exposure of at least 15 minutes. It’s just guesswork, really. But it works. I can see approximately how much distance the clouds move in, say 30 seconds, permitting me to estimate the amount of time it will take for them to travel sufficiently across the sky to appear as streaks.
    • Using my camera's built-in light meter, I take an exposure reading of the scene in manual mode at an ISO setting of 100 to match the sensitivy I've selected for my camera.
    • The meter indicates a shutter speed of 1/500 second at f/8.0 for correct exposure of the scene.
    • 15 minutes contain 900 seconds. So I need to figure out what density or strength of neutral density filter to employ for proper exposure at f/8 when I change my shutter speed from 1/500 sec to 900 seconds.
    • So, I count the number of stops between a shutter speed of 1/500 sec and one of approximately 900 seconds, and find there are nineteen. Here is the progression: 1/500, 1/250, 1/125, 1/64, 1/32, 1/15, 1/8, 1/4, 1/2, 1, 2, 4, 8, 16, 32, 64, 124, 248, 496, 992.
    • Neutral density filters are numbered to designate their degree of density, and therefore the amount of light they transmit. By referring to the ND Filter Grade table here, you can see that it would require three filters stacked in combination - one graded ND 4,0 (13 1/3 stops), one graded ND 0,8 (2 2/3 stops) and one graded ND 0,9 (3 stops) - to reduce exposure by 19-stops.

    I don’t have those particular filters, and would be reluctant to stack more than two filters at a time, to avoid vignetting, blocking light at the edges of the frame. I usually carry two neutral density filters - a 6-stop and a 10-stop filter - in my camera bag. They generally satisfy most of my daytime long exposure photography needs. How do I know which one to use, or whether I will need both?

    • The 10-stop neutral density filter will allow me to decrease my shutter speed by, not surprisingly, 10-stops and still achieve proper exposure.
    • It has a filter factor of 1024. Decreasing the shutter speed of 1/500 sec by a factor of 1024 [1024 divided by 500] results in a new shutter speed of 2.048 sec. This is unfortunately not slow enough to capture the motion of the clouds.
    • In order to slow the shutter speed further, I could reduce my aperture by a few stops, or I could stack another neutral density filter. Because I don’t need much depth of field in the image, I've elected to stack my 6-stop filter on the 10-stop filter. The factor for the 6-stop filter is 64, which results in a new shutter speed of 131 seconds, which is still too fast.
    • With no stronger filters to use, reducing the size of the aperture is my only option. Closing down the aperture from f/8.0 to f/22 allows me to decrease my shutter speed by 3 more stops (or a factor of 8) giving a final shutter speed of 1048 seconds or 17 minutes and 28 seconds, which is close enough.

    Water that is in motion - even ocean waves - can appear flat in an image exposed for a long time. The effect can be somewhat dreamy and unnatural, blurry or milky in some cases and as if the surface had frozen in others.
    Water that is in motion - even ocean waves - can appear flat in an image exposed for a long time. The effect can be somewhat dreamy and unnatural, blurry or milky in some cases and as if the surface had frozen in others.

    DAYTIME LONG EXPOSURE WITH A DIGITAL CAMERA
    Problems to be aware of.

    Many photographers feel that traditional film cameras are better suited for ultra long exposures, although you can expect some color shift and underexposure through reciprocity failure. Digital cameras have their own problems with long exposures.

    Electronic noise

    • Very long exposures with a digital camera will often produce excessive noise.
    • Noise (or electronic noise) refers to the grainy look you find in a digital image caused by image artifacts, often appearing as specks of color sporadically throughout an image. It is usually noticeable in shadow areas, and generally produced when shooting in low light. Noise is almost always unwanted and unattractive. To minimize it, you can select "Noise reduction" from your camera's menu, if available with your model.
    • The 15 minute exposure that I estimated in the example above prohibited me from using my entry level Canon EOS Rebel XSi digital camera, which (although it has a long exposure noise reduction option) is not as sophisticated as my new Canon EOS-5D Mark II D-SLR. When using the Xsi for a very long exposure, I’ve found that a maximum five-minute shutter speed is the limit for producing images with an acceptable level of noise. But, a 15-minute exposure with the EOS-5D is very doable.
    • You will need to experiment with your own model of camera to see whether you should limit your daytime long exposure photography as I do, and to what degree. If a fifteen-minute exposure is very noisy, try shutter speeds of six, seven or ten minutes.

    When my pictures display noise, I've found that the problem can be mitigated by converting from RGB (color) mode to Grayscale mode when I am editing the image on the computer, so the image appears as a black and white picture. An advantage of doing this is that many daytime long exposures seem to be more dramatic in black and white.

    The effect of infrared light

    Color shift is another problem associated with long exposures, due to infrared light building up on the camera's sensor. The ND filter does a good job of blocking out visible light rays. However, it does not effectively block infrared light, thus a longer exposure has an excess of this part of the light spectrum which caused the orange/red color shift in the example cloud streaks photo above (the middle picture). A solution can be found by using an IR Cut Off filter, which blocks the transmission of infrared light to image sensors, resulting in accurate color.

    Stacking three filters on a wide-angle lens caused the vignetting that is apparent in this photograph.
    Stacking three filters on a wide-angle lens caused the vignetting that is apparent in this photograph.

    The photo above is an example of a long exposure photograph taken at Vancouver's famous Kitsilano Beach. This picture was shot after a tremendous windstorm had beached several of the less than well-anchored sailboats moored in the bay. It was exposed for 10 minutes and is a good example for several reasons. The water is void of any noticeable ripples or waves. The clouds seen on the edges of the frame are somewhat streaky (although not as pronounced as I'd have liked).

    While I took this photo, the boat's owner and several other people were walking around in front of my lens, inspecting the beached craft. However, they remain unseen in my picture since they were moving, and their movement as they walked normally, without having to be hurried along, was too quick to be captured in the long exposure.

    This shot also illustrates a problem caused by stacking too many filters in front of a wide-angle lens. Significant vignetting can be seen in the top two corners (less so in the bottom two). This is the result of my placing three filters on the lens - a UV filter, which I usually keep on all my lenses, and two neutral density filters (a 10-stop and a 6-stop). The end result, though, could be a matter of preference. I find the vignetting actually adds to the look of this particular image, encircling the subject in what I think is an attractive way. In other circumstances, the effect might be undesirable, and could be reduced or eliminated by removing the UV filter, using one ND filter that is as dense as the two I employed, or switching to a longer lens.

    Having an element in motion is important to a good long exposure image, but don't overlook the greater importance of an interesting subject.
    Having an element in motion is important to a good long exposure image, but don't overlook the greater importance of an interesting subject.

     
    Further information...
    Infrared light's effect on digital photography
    Night photography
    Evening photography
    Infrared digital photography
    Exposure meter
    Shutter speed guide
    Shutter speed/aperture combinations
    Slow shutter speed
    Related topics...

    Neutral density filter

    Reciprocity failure

    Shoot the moon

    Slow shutter hand-holding

    Star trails

    Fireworks