A beginner’s guide to shutter speed.
What is shutter speed?
When the photographer aims the camera at something and takes a picture, he or she is making an exposure. An exposure is the net result of a combination of several mechanical, chemical or electronic factors working together in unison.
An exposure fixes an image in time, and can be considered “proper”, “under-“ (meaning too dark), or “over-“ (meaning too bright).
Aperture, shutter speed and ISO are the three primary adjustments that affect exposure. In a proper exposure, a change to any single one of these will necessitate an equal and opposite change in at least one of the others. This truth is known as equivalency.
The simplest definition of shutter speed is that it is the length of time that light is allowed to enter into a light-tight box (known as a camera) in order to produce an exposure.
A shutter is a physical device, a door if you will, that literally opens and closes to start and stop an exposure. Shutter speed is the duration that the door remains open. While aperture controls the amount of light entering the camera, in the sense that a larger opening will let in more light, a longer shutter speed will enable photosites on the digital sensor or the chemistry on film to react more intensely to the quantity of light received, this is why a larger aperture (smaller f-number) and a longer shutter speed will each produce a brighter exposure.
In most modern DSLRs the shutter mechanism consists of two metal curtains positioned in front of the focal plane (as opposed to inside the rear of the lens) that open and close vertically or diagonally, instead of horizontally. This is because a vertical/diagonal action reduces the distance that the curtains have to travel, enabling both longer exposures and expanded flash synchronization. Being in-camera (thus better protected), focal-plane shutters have the benefit of being more reliable, long term, than in-lens shutter options, and modern versions rated between 100,000-300,000 actuations are far better than what existed even a few decades ago.
Only at slower speeds is the entire focal plane exposed. At faster shutter speeds, the second shutter curtain begins to close before the first one has fully traveled across the focal plane (think of windshield wipers). The fastest speed that the entire focal plane remains exposed is generally the camera’s maximum flash synchronization speed; if flash is used at a shutter speed faster than this, the resulting image may feature a blackened out portion in the final image, which is a shadow cast by the second curtain as it is closing.
Some cameras utilize what is known as an “electronic shutter”, which uses scans of the digital sensor to increase shutter speed beyond the camera’s mechanical capabilities. Electronic shutters have the potential to increase max flash sync speeds, but the technology is not exactly there yet. In the interest of the beginner, I will leave a more in-depth explanation out of this posting.
What does shutter speed do?
We have already established that shutter speeds control the duration of an exposure, and the best way to observe this is with regard to motion. The longer that a shutter is open the easier it is to record the physical movement of a subject being photographed. Conversely, a very short shutter speed has the ability to “freeze” even very fast motion. More on this later…
Shutter speed dial on my Bronica ETRSi.
Similar to aperture, shutters speeds are measured according to a sequence of stops (a geometric formula equating to one-half or twice the duration of light, depending on which direction one moves on the sequence). The most common sequence encountered in modern cameras ranges from 30 seconds to 1/4000 of a second, and looks something like: 30, 15, 8, 4, 2, 1 (second), then goes the reciprocals, 2 (1/2), 4 (1/4), 8 (1/8), etc. Some cameras allow mechanical speeds ranging from bulb (set by user up to a maximum time) to 1/8000 of a second. The stops between shutter speeds have a direct and equivalent relationship to the stops between apertures (and those between ISO values).
How should the beginner use shutter speed?
Most photographers see aperture as the most creative of the three core adjustments affecting exposure (aperture, shutter speed and ISO), but shutter speed, because it can actually show time passing or freeze it altogether, offers some really intriguing photographic affects, if you are willing to work for them.
Creatively, shutter speed can be used to define movement of a subject in your work. Want to freeze the action of that runner as he/she slides into homeplate? Shutter speed can do that for you. Want to emphasize the velocity of the pitcher’s arm as they launch a 90 mph fastball? Shutter speed can do that too. Likewise, shutter speed can be used to heighten tension, suggest grace, illustrate the earth’s rotation, solve bets (see Muybridge below), etc.
In 1878, Edward Muybridge solved a bet between two businessmen about whether all four of a horses legs ever leave the ground at once by using shutter speed (and some clever flash triggers). This sequence of images helped lead to the development of motion pictures.
A couple of the techniques open to the beginner to explore using shutter speed include dragging the shutter and panning.
Dragging the shutter is a technique often used in wedding and event photography, especially when combined with flash. Dragging the shutter simply means shooting a scene at below the minimum shutter speed needed to prevent motion blur and/or camera shake. Combined with a flash, the slow shutter speed will increase ambient light, but the flash will freeze the primary subject (even at speeds that typically could not do that); with some careful application, the resulting photograph can have a very natural light quality that using flash and a fast shutter speed would not necessarily achieve. If you want to experiment with this, I recommend using rear-curtain or second curtain sync as your flash mode (set on-camera).
Dragging the shutter blurs the taillights of cars on the road, and allows increased ambient light.
Panning is a way to suggest that something is moving fast.
Panning is accomplished by locking focus on a fast-moving subject, and “following” them with your camera. The resulting effect is that the subject will be frozen in action while the background will be a blur.
Below are some rules of thumb to consider, regarding shutter speed.
- To achieve maximum image sharpness and minimize camera shake (blur that you cause through handheld camera operation), you should understand that the faster your shutter speed, the less of a factor motion and vibration are. As for camera shake, it is a general rule of thumb to shoot the reciprocal of your focal length as a minimum shutter speed (ie. 200mm lens = 1/200th second shutter speed) in order to eliminate camera shake. Note: Using crop sensor cameras and/or high megapixel cameras can have a negative impact on this rule. If you are in that boat, definitely experiment to see what works for you.
- Minimum shutter speeds to freeze common activities include: Speech (1/60th-1/125th), Human Walking (1/125th-1/250th), Human Running (1/500th-1/1000th), Sports and Wildlife (1/500th-1/2000th), Race Cars (1/1000th-1/8000th).
- To minimize camera shake when a tripod or monopod is unavailable and you must shoot at speeds below the rule outlined above, brace yourself against a wall, ledge, counter, etc.- snap the picture as you exhale. To shoot vertically, position the camera so that the shutter button is below the lens (rather than above it with your elbow out), and keep both arms close to your body.
My son demonstrating pretty good camera holding.
- Use Shutter Priority when you absolutely cannot shoot below a certain speed, and the shot is more important than depth of field. Note: Exposure compensation (EV or AV) is available in this mode.
- Lenses that have a smaller constant f-number setting (ie. f/1.4, f/1.8, or even f/2.8) are considered “fast” because they allow the photographer to use faster shutter speeds in order to freeze action, especially in lower light scenarios. Though faster lenses are usually more expensive when compared to their slower counterparts, exceptions exist. For instance, Canon and Nikon’s 50mmf/1.8 lenses are among the best bargains in photography.
However you choose to use the information provided above, most important to your development as a photographer is to get out and make photographs. Every moment you spend snapping pictures is a step toward lessening the barrier between the photograph you envision and the one you actually take.
More lessons on photography here.