David Hayden Photography
All in Due Time!
The first article in this series introduced you to the light / exposure triangle. The second article discussed aperture. This article is going to delve into another aspect of the exposure triangle, time.
If you read the first article, https://www.davidhaydenphoto.com/post/did-the-illuminati-foretell-modern-photography, you know photographic exposure is a blend of aperture, time and sensitivity of the photographic medium. In the world of digital photography, sensitivity is referred to ISO.
A recap of the Exposure Triangle
Another useful simile for the light triangle is one that involves volume. Not in the rock and roll sense of crank up the volume, but practical sense of measurement.
Imagine for a moment you want to fill a tray full of glasses with water. You could:
Use a large aperture method and pour a bucket of water over the tray, this would require a short amount of time.
You could use a hose, a smaller aperture, but still fast and somewhat slower than the bucket.
You might use a bottle and carefully fill each glass; this would work well but take more time.
And, you might want to be very precise using a teaspoon.
Using any of the above methods, you will fill the glasses, the only difference is the amount of time.
Digital sensors are like the glasses of water in that you can think of them is tiny vessels in which the camera catches photons. On a very bright sunny day, the source of photons is very large and like the bucket fills our sensor very quickly. So, we use very fast shutter speeds to reduce the volume of light hitting the sensor.
Of course, the opposite is true in a dark environment, it takes more time to collect enough photons to achieve the exposure we want.
Just as there are no absolutes in composition, there are no absolutes in shutter speed. The proper shutter speed is the one that captures your intent as an artist. In the image above, the assignment was to capture liquid pouring into a shot glass for a fictional magazine cover. I chose to freeze the action.
Freezing action takes a shutter speed that is faster than the movement taking place. In the case of the image above the camera was set at 1/250 of a second, but the light source was a speed light that gives a strong burst of light in 1/1000 of a second or less. The exposure time was determined by the light source, not by the shutter speed. The shutter speed was chosen because it synced well with the speedlight.
When you have less control of the light and want to freeze action, you must depend on shutter speed. In the following picture to freeze the splash in the evening sun, I used a shutter speed of 1/640 per second. There was enough light that I could use a smaller aperture F/10 to have the depth of field I wanted while maintaining a low ISO (100). If you look close enough you will see there is still some motion blur even at 1/640/s.
Speed is relative
The shutter speed you choose, as mentioned above, is determined by the effect you want, the motion in the scene, your focal length, and of course the available light. Look at the two images below. Both are of the stars but the focal length of the lens was dramatically different and therefore the shutter speeds had to match accordingly.
This first image is a highly cropped image of M42, the Orion Nebula. It was shot at a focal length of 560mm, with a shutter speed of 2 seconds, and if you look closely, there is some perceptible motion blur.
The following image of the Milky Way is only slightly cropped but was shot with a wide angle 20mm lens with an exposure time of 20 seconds. 10 times the exposure time but much less perceptible motion blur.
Like most things in photography, there are many variables that can be coordinated to render our artistic intent.
Try this experiment. Using your longest focal length, handhold the camera and take a picture of something very close at the slowest possible shutter speed.
Then, still handholding the camera, use your widest-angle focal length, and take a picture of something very far away using the same shutter speed as before.
Is there a noticeable difference in motion blur?
Slow down cowboy!
Motion blur is neither good nor bad, it is just another aspect of photography that can be used to our advantage. There are a couple of ways to use motion blur to soften an image, create a sense of motion.
Depending on your vision you may want to shoot a brook or stream and freeze the motion of the water splashing off the rocks as in the image above (F/13, 0.8 seconds, ISO 50.
Or you may want a softer look that still implies motion but has a more serene affect as in this picture.
You know the water has ripples and texture but “dragging the shutter” for 25 seconds allowed me to achieve a very soft appearance to the water. The result, in my opinion, is an image that evokes the calmness of a late evening.
It’s a good idea to mix things up a bit.
We’ve all seen the pictures of a car or motorcycle racing in front of the camera. The subject is pretty sharp but the background has a lot of motion. This effect gives us a real sense of motion.
The technique for achieving this result is called panning. In theory, you follow the moving object as closely as possible using a slower shutter speed. By following the subject, its motion is frozen while the panning across the background gives it a lot of motion blur.
In this image taken with a 100mm lens at 1/240 per second shows a bit of what I’m describing. By following the rider to minimize their motion, the background picks up the motion blur and gives the image a sense of action and excitement.
It’s funny. In searching my images for some panning shots, I realized I had very few. It appears, at least as of now, my predominate style is to stop action. I’m going to have to work on that.