Monday, January 4, 2010

Night Photography: Pushing the Limits, Understanding the Obstacles

Las Vegas at NightPhotography at night has plenty of obstacles, but is also full of rewards for travel photographers.

Many locations have interesting sights and looks during the day, and a whole host of different sights and looks, and another atmosphere in the evening. Las Vegas many interesting photographic opportunities during the day, but it seems as though it’s at night that Las Vegas really comes alive. The night photography opportunities in Las Vegas are almost limitless.

Paris at night: view from the Eiffel TowerAnother location with great night photography opportunities is the “La Ville-Lumière” (The City of Light). While Paris, France, was originally given that nickname due to its fame as a center of education and thought during the Age of Enlightenment (eighteenth century), its early adoption of street lighting (In 1828, Paris began lighting the Champs De Elysées with gas lamps. It was the first city in Europe to do so.), and its use of electric light beginning in the 19th century for street lighting and later to illuminate monuments established the nickname forever.

The goal of many travelers when taking night photographs is to capture that great evening look, as they find it, when exploring a destination after sunset comes and darkness falls. But nightfall also brings with it opportunities to capture motion in photographs via streaks of light from moving vehicles, etc. Streaks of color showing motion can bring real life to a night photograph.

Philadelphia at night: The Schuylkill ExpresswayNight photography pushes any camera's limits of shutter speed and aperture, and digital cameras’ limits on its sensor qualities. Night photos are often highly technical, and can push the photographer’s technical and creative limitations “to the max,” as well.

Historically, film photographers had great difficulties capturing night scenes because they require very long exposures to maintain reasonable depth of field, and if more sensitive film was used, it produced so much grain in the photographs that they were never printed.  Film unfortunately has something called reciprocity failure. That means that as the exposure time increases more and more light must expose the film. The law of diminishing returns rules.

With Digital cameras, both DSLRs and Point and Shoot units, the limits imposed by reciprocity failure no longer plague photographers, however, digital cameras are not without limitations and obstacles. The biggest problem is the trade-off between exposure time and image noise. Even with great advances in digital sensor technology, the longer the exposure the greater the digital noise, and unfortunately the noise is most evident in the black areas of night photographs where it’s most noticeable.

Boat House Row in PhiladelphiaWith the low light conditions of night, the challenges don’t stop with exposure, and noise. Focusing in low light conditions is difficult. If you’re taking a photo of a building well illuminated at night focusing isn’t generally an issue, but if your scene is less well lighted, your camera’s auto-focus system may not be able to lock on to the subject. Moreover, if you’re manually focusing, you may not even have enough light entering your viewfinder to properly focus the camera.

Sharp focusing is crucial at night because the margin for focus error is generally very small.

Understanding depth of field is critical at night because is can save the photographer from small mistakes in focus. Generally small apertures which give the greatest depth of field are unavailable to the night photographer when the exposure decision balancing ISO (sensor sensitivity), shutter speed, and aperture is made. The lower the ISO the less tendency for noise. The higher the shutter speed, the less any camera/lens movement can affect the photograph.

Often photographers need to set the focus by estimating distance and use the lens’ depth of field to keep the focus sharp. Often photographers make the mistake of setting their focus to infinity, but that is a poor use of depth of field, as you only get limited extra focus in the foreground, not the background. Focus is one of the crucial areas the night photographer must be technically aware.

For SLRs or DSLRs, the movement of the mirror can negatively affect the sharpness of the photograph by causing a slight movement of the camera via mirror-slap. Many DSLRs can use mirror lock to eliminate the problem.

San Francisco's Bay BridgeFor determining exposure photographers must reconcile the fact that most in-camera exposure meters loose their accuracy or max out at a shutter speed of about 30 seconds. Determining longer exposures requires the night photographer to understand the mathematical relationship between the three exposure parameters of ISO, shutter speed and aperture. Manually adjusting these three exposure controls may be necessary.

Night scenes, more often than not, have a decidedly low key histogram. When they don’t, it generally means the photograph will have blown highlights. When metering, in order to avoid blown highlights to the extent possible, yet avoid underexposing the image to the point the desired details blend into the darkness, exactly what portion of the scene is metered and the metering method becomes critical.

Getting the look of the photograph “right” is part of the art and creativity the photographer brings to each night shot. For example, underexposing the photo can produce a dark look of night but may loose important detail, or using a more normal exposure will show a histogram filled along the entire tonal range like a daytime shot.

Now that we understand the basic problems and obstacles facing travel photographers taking night images, next week I will discuss how to overcome them, to produce wonderful night images which help tell one’s travel stories.


amit said...

hey the oakland Bay Bridge picture is jus fabulous..nice capture..

Ned S. Levi said...

Thanks very much.



Mark said...

Can't wait for next week Ned. I'm sure it will be a good one.


Romantic bed and breakfasts said...

Night photography has its own charm and excitement.The photography at night is more unique and wonderful and gives a strange and amazing look.

Steven said...

Ned, I've pushed my ISO all the way to 1000 to capture indoor shots hand holding my camera with almost no ill effects. You write that in night photography noise is a problem for night shots. Can you explain? Why would I have a problem?

Ned S. Levi said...

Hi Steven,

With night photography new parameters come into play. Sensors that are virtually noise free at high ISOs at 1/30 sec are not necessarily noise free at 3-5 sec exposures. Plus significant portions of black and other dark areas in an image, will show up noise far worse that lighter areas of an image.

You mentioned you've had no problems with high ISO when hand holding your camera for various photos. That means you've probably used shutter speeds for those photos at 1/30 second or shorter. At those shutter speeds you are balancing the ISO with regard to noise, so you haven't seen noise in those photos. You probably have a "newer" sensor which has better noise characteristics than older ones, but, under the "right" circumstances, even with it, noise can be a problem.

The longer the shutter speed, and the more areas of the photo which are dark the more likely noise will be evident at high ISO settings.

Personally, I prefer to keep my ISO at 400 or lower, and actually try to keep it at 100 if at all possible.

montreal florist said...

Night photo with lights is fantastic mood. Great shot!

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