ONLINE DIGITAL PHOTOGRAPHY COURSE

LESSON 2 - Camera Tutorial, Part 3
(Shutter Speed and Freezing/Showing Motion)
Article by Stephen J. Kristof
© 2010, all rights reserved

The Shutter

What is this magical device inside every camera that holds the secret to both showing and freezing a moving subject?  The shutter controls the LENGTH OF TIME light is allowed to enter the camera.  This is very important, because longer exposures will allow more light into the camera, while shorter exposures will allow less light in.  The shutter speed also has a lot to do with ‘speed clarity’.  In other words, faster shutter speeds will allow you to get clear pictures of faster moving subjects, while slower shutter speeds may blur moving objects of people (called motion blur or smudge). ).

The numbers listed below are actually fractions of a second:

            "30" is 1/30th of a second               "60" is 1/60th of a second  
     "125" is 1/125th of a second         "4000" is 1/4000 of a second

Shutter Speeds on the common camera
 (all are fractions of 1 second)
4000 - 2000 - 1000 - 500 - 250 - 125 - 60 - 30 - 15 - 8 - 4 - 2 - 1 - B
very fast                           moderate                   very slow      


"B" stands for "Bulb" and it allows the user to keep the shutter open indefinitely (for as long as
the user wants).  DSLR cameras have exclusivity when it comes to this feature.
(Most DSLR cameras will allow incremental pre-programmed long exposures beyond 1 second;
generally being: 1, 2, 5, 10, 15 and possibly 30 seconds each.  However, if you want more specific
control over exposure length or want to hold the shutter open in excess of 15 or 30 seconds,
you will need to use this BULB feature.  You will also need to get a digital bulb cable
or use the wireless remote control that comes
with your camera.)



REMEMBER...
The higher the number, the SHORTER the exposure time.
The lower the number, the LONGER the exposure time.
 


A short shutter speed will allow light in for a very small fraction of a second,
which is fast enough to stop or freeze the MOTION of a very fast moving object.

The visual helper below demonstrates how a galloping horse takes-up a certain amount of horizontal space in a given amount of time.  What happens when the shutter is open for longer periods of time?  The horse and jockey will occupy more of the vertical space.  With increasingly long shutter speeds, it will appear more and more like a semi-transparent blur.   (ie. 1/500 of a second is a very short amount of time compared to 1/30 of a second.  Although 1/30 of a second sounds like a very short amount of time, it is relatively long in photographic terms.)

See below:

As the amount of time that the shutter is open increases, the horse occupies more of the frame and, consequently, appears blurred and semi-transparent.

Confused?  Relax, you're not alone, and it's not that difficult to understand.  You probably just need another example to get your head around this concept!

First of all, understand that a camera's ability to "freeze" the motion of a fast moving object so that it appears crystal clear in a photograph, is relative to the amount of time for which the shutter is open.  You may not have ever considered that a moving object will look increasingly blurry with increasingly long shutter exposures.  Then again, why would anyone consider this relationship unless their hobby or profession were photography?

THE WATERMELON DROP...Think of it this way; imagine that your friend drops a watermelon from the top of a 10-story building.  Science tells us that an object without undue resistance will hit the ground in about 3 seconds as it travels this 100-foot length drop.  Technically speaking, the object will accelerate as time progresses, but for the purpose of more easily understanding this concept, suffice it to say that it is traveling at a constant speed of 33.3 feet per second (400 inches per second).  Therefore, if the camera's shutter is open for 1 full second and the camera is perfectly still on a tripod, the resulting image will depict a perfectly clear building with a long vertical 400-inch greenish semi-transparent blur in the physical space in which the watermelon travels during that 1 second exposure.

With all things remaining constant, the camera's shutter speed is next set to 1/2 second; the blurry vertical streak in the image will now be half as long, at 200 inches along the side of the building.  At 1/4 second, the streak will be shorter, at 100 inches, but still extremely stretched and blurry.  Even the "standard" shutter speed of 1/60 of a second, the watermelon will appear quite blurry, taking-up 6.7 inches of vertical space greater than that of the watermelon itself.  In order for the watermelon to appear truly clear, the shutter speed would need to be in the range of 1/2000 of a second.  At that speed, the watermelon will take up its own space, plus a mere .2" spread - not enough to show blur from the shooting distance.  (In fact, the falling melon might also appear acceptably clear at longer shutter speeds of, for instance, 1/800 of a second.)

See below for a visual illustration of this watermelon drop discussion:

See how the watermelon takes-up more vertical space and blurs with longer exposure times.

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---

Still need more of an explanation?  Imagine how far a person can walk in one second. Look at the visual example below for a representation of the distance that person travels from point "A" to point "B".  In reality, this scale may represent about 1 yard (apx. 1 meter) if they walked at a normal pace.

"A"------------------------------------------------------------------------------------------------------------------------"B"
    The yellow dashes represent a distance of 1 yard walked in 1 second.

    If the shutter speed was set to 1 full second, the walking person would appear as a long blurry, semi-
    transparent streak from point "A" through to "B".


Now, if the shutter speed is set at "60" (meaning 1/60 of a second), it will open for 1/60 of a second. That would capture this much movement shown in the yellow part of the dashes shown below:

"A"------------------------------------------------------------------------------------------------------------------------"B"
(A to B distance traveled is 1 yard in 1 second)

That's right - there are 120 dashes in the light blue line above.  Therefore the 2 yellow dashes represent 1/60 of the entire line.  If it takes 1 second for a person to walk from point "A" to point "B", then the distance he or she would cover in 1/60 of a second would be equal to the 2 yellow dashes (in real terms, if they walked 1 yard/meter in the full second, they would have traveled about 0.6 inches or 1.5 cm in that time).   If the subject was shot at a shutter speed of 60, it would appear a bit blurred, as about 0.6 inches of movement would be recorded in one frame.



Now let's see what happens to the yellow portion if the shutter speed is set to "125" is used:
 
"A"------------------------------------------------------------------------------------------------------------------------"B"
(A to B distance traveled is 1 yard in 1 second)

This new shutter speed exposes the digital chip for only 1/125 of a second. That would capture only 1 dash on the blue  line. The actual distance recorded during that short shutter opening would be about 0.25 inch (0.6 cm). This is too little of a distance to create any motion blur. The subject shot from a reasonable distance, would appear very clear without motion blur.



Next, if a shutter speed of "4" is used it will be open for 1/4 of a second. That would capture the following distance shown in yellow below:

"A"------------------------------------------------------------------------------------------------------------------------"B"
(A to B distance traveled is 1 yard in 1 second)

The actual distance recorded during a "4" (or 1/4 of a second) shutter speed opening would be about 9 inches (23 cm). This is a long distance that would definitely result in major motion blur.

What shutter speed should I use to photograph very fast moving things?
Consider shooting a fast moving car at a car race, athletes at a ball game or some other fast moving subject. What shutter speed would you choose to freeze this very fast moving motion? (At least 1/1000 of a second.)


What's the most common shutter speed?
The most common shutter speed for most non-action purposes (a sort of default shutter speed) is 1/60th of a second. It is fast enough to get a clear image of landscapes, objects and people who are not moving (as long as you keep your camera very still when shooting the frame). As your subject matter (or as the photographer) begins to move increasingly faster, you will need to use increasingly faster shutter speeds in order to end-up with clear rather than blurred images. If you try to photograph generally stationary subjects and you do not have a tripod, a shutter speed of 60 is about the slowest most photographers would recommend. Even though your subject is still, hand-holding the camera creates enough movement to show a motion blur at speeds of 1/30 or slower. This explains why your camera will tend to blur indoor photos on the automatic exposure settings when you shoot without a flash. The camera recognizes that there is little light available in the indoor venue and compensates by having the shutter open for a longer time which is another way of allowing more light into the camera. The result is a properly exposed image that unfortunately has smudge or motion blur.


What shutter speed was required to freeze the motion of the following subjects? (see below:)

Note how the water droplets (in the photo above left) are frozen and clear, as if they are individual droplets floating in space. The high/fast shutter speed of 1/1000 of a second ("1000 in photographers' terms) is fast enough to freeze the splash and spray of the water. The photo of the yacht to the top right was shot at half that speed; 1/500 of a second. Because the yacht is not traveling at a high rate of speed the lower shutter speed is more than adequate to freeze it in place and preserve perfect focus.

The photo to the left was shot at 1/500 of a second, which is too slow to capture the high rate of speeds at which these acrobatic jets are flying. The result is called "smudge" or motion blur. The lens was pre-focused on the jet path, yet the speed was too much for a shutter speed of 500. Interestingly, 500 is a very fast shutter speed, but no match for this motion; particularly when zoomed-in to a tight relative proximity as was this shot. Note how the clouds in the background are clear and show no motion blur, as the shutter speed is far more than adequate to freeze any cloud movement or minor camera movement that might be caused when the shutter is depressed.

The subject in this photo to the right is a similarly fast acrobatic aircraft, but note how the extremely fast shutter speed of 1/4000 of a second perfectly freezes not only the fusilage of the plane, but the propeller as well.

Did you know that in order to get high quality, high-speed photos like the one to the right, you need to "graduate" to a digital single lens reflex (DSLR) camera, like the pro's use?  FreePhotoCourse.com is your first and last stop for today's top-selling, high quality DSLR cameras and gear, powered by Amazon's low, low prices and fast service!  Click the image below to get to our camera and gear store, where you'll find our DSLR selection chosen specifically for our photo learners!

 

LUCK or SKILL? The soccer photo above is fantastic, because a slower shutter speed was used experimentally with a stunning result. A tripod was used to eliminate any motion blur of stationary elements in the image.  The soccer player's leg had just kicked the ball, but then lingered in mid-air for a few seconds after making contact with the ball. The legs and feet are therefore perfectly clear as they are relatively motionless. But that shutter speed of 125 is too slow for the accelerating ball which shows fantastic motion. Best of both worlds!

The Blackhawk helicopter above on the right was traveling at a speed that required a shutter speed of 1250 in order to show the fusilage as clear but with a motion blur in the propellers. However pushing that shutter speed to 2500 freezes the propellers as well.

 

The photo of the F-18 fighter jet above left requires an extremely fast shutter speed. With the subject traveling at a speed close to Mach 1 and using a 400mm lens zoomed-in close to that subject, these are factors that represent a photographic challenge ; the 1/4000 shutter speed is a necessity.

The photo above to the right is a night-time rocket launch of NASA's Mars Phoenix project. You might think that a rocket would require a shutter speed even faster than would be used for the jet, but in reality, this initial stage of lift-off is not yet "rocket fast" and 1/500 is definitely adequate as you can see in the clear shot above. Adding to this is the fact that in the night sky, a shutter speed shorter than 1/500 may not have allowed light in the camera long enough for an adequate exposure.

THINK ABOUT THIS...

You should now understand that we need a very fast shutter speed to freeze the motion of very fast moving objects and the reasons behind this.

You should also now know that the default shutter speed for everyday photography of relatively still subjects is 1/60.

Why, then, are there shutter speeds slower than 1/60 on a camera with manual controls?  (Keep in mind that some shutter speeds are far slower than fractions of a second and are open for multiple seconds.)


Click HERE for the answer!
(This will take you to the Camera Tutorial, Part 4.)

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