THE SHUTTER

Between your lens and the light sensitive sensor of your camera is a door known as the shutter. The shutter is attached to a timed mechanism allowing it to open for a predetermined amount of time exposing the sensor to light and then close again.

If too much light strikes the sensor, your image will be too light. If too little light strikes the sensor, your image will be too dark.

The shutter is one of three adjustable variables that work together to create a proper exposure. The other two are your aperture discussed in the previous post, and ISO which will be addressed in the next post.

For typical photography, the amount of time the shutter remains open, in normal terms, is quite short, typically in the hundredths of seconds.

The primary purpose of the shutter, is of course, to ensure the correct amount of light strikes the sensor. However, during the time the shutter is open, a lot can happen. Even when that amount of time seems to be incredibly short.

Your image is being created while the shutter is open so any movement of your subject or your camera will be recorded. Sometimes, movement during the exposure is desirable. For example, longer shutter speeds are intentionally used for photographing flowing water in order to get a silky look.

1.5 second exposure, f22 ISO 100

By leaving the shutter open 1.5 seconds, the fast moving water had an opportunity to blur enough to get the look I was attempting to achieve but the rocks and foliage, which weren't moving, remain sharp. In order to prevent over exposing the image, you'll notice I've shot at f22, a tiny opening, and have lowered my ISO setting to 100. More about that in the next post.

Another application for using long shutter speeds is shooting fireworks. Many photographers struggle with fireworks for a couple reasons. Firework displays happen at night when its dark and so we get fooled into believing the settings required should be for dark situations. Which is correct, kinda. You see, the exploding fireworks themselves are incredibly bright. The explosions can light up the area quite nicely but only momentarily. More importantly however, is the fact that fireworks are actually moving subjects. They are a series of burning bits of various chemicals being thrown from a centralized airborne explosion. If you want good fireworks images you absolutely must leave the shutter open long enough for the explosions and the travel of the burning embers to create the streaks we see.

17 seconds, f11, ISO 200

You can see that my aperture is set at f11. That's a really small aperture to be using when its dark outside. But its necessary for proper exposure of the very bright fireworks. If a larger aperture was used, the fireworks would be totally overexposed because of their intensity. During the 17 second exposure the reflecting pool and other darker parts of the image had a chance to be properly exposed using this small aperture. Since the fireworks, while incredibly bright, are only in the image for a few seconds and then gone, the long exposure combined with small aperture allows everything to be properly exposed. 

Sometimes you might just want to show motion in your picture to illustrate movement.

1 second, f11, ISO 100

With all three examples shown above the camera was on a tripod because otherwise even the stationary things would be blurry. Even with image stabilized lenses and camera bodies, its not realistic to hand hold a camera for exposures as long as these. 

Remember, while the shutter is open, either the subject can more OR the camera can move. Or both, of course. One of the leading causes of unsharp images is actually camera movement. 

Much shorter shutter speeds are typical for average shooting, especially during daylight hours. Speeds in the hundredths of seconds are normal. In fact, I recommend never trying to hand hold a camera if the shutter speed is less than 1/100th of a second. 

When I teach beginners I reinforce the concept that shutter speeds like 1/125th or 1/250th of a second might seem incredibly fast but its quite possible to get camera movement at these shutter speeds. Its often subtle and only apparent when the images are magnified so on the back of the camera things might look fine but...

1/250, f11 camera held steady

1/250, f11 camera moved during exposure

As you can clearly see, the bottom image has lost its sharpness due to movement during the exposure - a 1/250th of a second long exposure! 

In my basics classes I demonstrate exactly how to properly hold a camera, and how to slow down their breathing, gently squeezing the shutter button as they exhale, etc. These skills are crucial for sharp images. 

Additionally, I always encourage photographers, especially those just developing their skills, to consider using supports for their cameras whenever practical. Tripods are the best but there are many things you can consider. Is there something you can lean against or brace the camera with? I've used just about everything from sandbags to doorstops and even my wallet to assist in stabilizing my cameras.

If you are using longer focal length lenses, the magnification they're providing for your subject will exacerbate the camera movement problem so this all becomes even more important. 

Even with decades of experience I'm not immune from camera movement. I carry a monopod with each of my camera bags. And, of course, there are definitely times I carry a tripod as well. 

If you're unfamiliar with the concept of a monopod, as its name would suggest, its only got one leg. Unlike a tripod, you can't just put your camera on it and walk away, although I don't really suggest doing that with a tripod either. However, monopods definitely provide additional stability because gravity is working for you rather than against you. 

As you'll see in this photograph of one of my monopods, I have mine equipped with quick release ball heads. The quick release encourages me to use it more than I would if attaching and removing the camera were cumbersome, and the ball head allows me to tilt the camera and yet retain stability.  

So back to shutter speed...

We've established that things move while the shutter is open. What if want to stop them? Frankly, for most of our photography that's probably the case. 

For typical photography with normal focal length lenses, shutter speeds between 1/125 and 1/1000 are probably the most practical. 

As shutter speed increases, movement begins to stop. In the higher hundredths you'll begin to stop your own movement as well as slower moving objects like this dragonfly. 

The dragonfly was relatively stationary although his wings remained a bit busy. However, in this case, the location forced a less than ideal shooting posture. I picked a shutter speed of 1/500 to stop any movement from either the dragonfly or my camera. I captured a good image and managed to avoid falling into the water below so win-win.

1/500, f6.3 ISO 800

As the speed of your subject increases, your shutter speed must do so as well. Here I wanted to have that frozen water look. 

1/1000, f3.5 ISO 200

But falling water isn't moving all that fast. What about something faster? Albeit a smaller RC copter at a local park, the rotors of this helicopter were moving fast enough it took a 1/2000th to capture them without blur. 

1/2000, f 11, ISO 2000

But if you get really fast moving subjects even 1/2000th may not be enough. To stop the movement of this drag racer moving close to 200 mph enough to see the wrinkles of the tire required 1/4000.

1/4000, f 7.1, ISO 1600

Most of us will rarely shoot anything that requires a shutter speed much faster than 1/4000, or even 1/2000. However, I had a challenge. I've been involved with drag racing almost as long as I've been involved with photography. I've told many people that by the time Top Fuel dragster crosses the finish line at around 330 mph, their tires are totally deformed and no longer round. Few people believe me. I mean, after all, how is possible that a tire traveling at those speeds can be anything but perfectly round? 

The answer is a combination of stress factors, aerodynamics and the 12,000 lbs of  downforce created by the rear spoiler wing. Here after more failed attempts than I care to admit to capture a close up of one of these rockets crossing the finish line, is the proof.  Look at those tires! An award winning photograph this is not. But it fully captures exactly what I needed it to and at a slower shutter speed it would be nothing but blur.

By the way, if you think that deformity is wild, you should see what happens during the 6g deceleration caused by the twin chutes that were being deployed at the very moment this image was captured! 

1/8000, f5.0, ISO 1600

As you can see, along with controlling the amount of light reaching the sensor, your shutter can have a huge impact on the images you create. 

Your shutter speed, aperture and ISO all work together to properly expose your image. Since all three work to increase or decrease our exposure, we can juggle our settings as needed. One, or occasionally two, will always take priority. For me, shutter speed is the setting that finds top billing most often. 

Most of our cameras have two semi-auto modes, aperture priority and shutter speed priority. With each of these modes, the user chooses the setting they want to prioritize, allowing the camera to adjust the opposite automatically. Its incredible to me how many photographers I hear about shooting in aperture priority vs shutter speed priority. Since shutter speed can have such an impact on my images I usually want to keep a very close eye on it.

Next up... ISO