Nature Photography, LLC
May / June, 2014
Tying It All Together: Shutter Speed, Aperture, and ISO
Now that we have covered the three basic elements of exposure individually (ISO - November, 2012 newsletter; shutter speed – March, 2014 newsletter; and aperture – April, 2014 newsletter), let's look at how they work in combination to give a properly exposed image.
All three control how much light hits your camera's sensor (or film), and each has its own function. But how do they affect each other? To explain it, let's once again go back to our window analogy, but this time, we need to add an additional element. Instead of simply trying to get a certain amount of air into a room, let's put a tabletop windmill in front of the window. Our goal: to make the windmill complete a set number of revolutions (let's say 10) -- a proper exposure. We know that aperture is the equivalent of how far we open the window, while shutter speed is how long we leave it open. We can throw the window wide open, let in a lot of air all at once and reach those 10 revolutions quickly. This also requires that we close the window quickly, before we reach 11 revolutions (or the windmill gets overexposed). This scenario is the equivalent of a large aperture and a fast shutter speed. Conversely, we can open the window only a little, which requires that we leave it open longer to reach the same 10 revolutions. If we close the window too soon, we will not have reached the magic number of 10 (the windmill will be underexposed). This is the small aperture, long shutter speed scenario. But wait, you say, doesn't the speed of the air moving through the window also help determine how fast the windmill reaches 10 revolutions? Excellent catch! Indeed it does, and this is where aperture comes in.
In this analogy, the strength or speed of the air moving through the window is the equivalent of the strength, or brightness, of the light hitting the camera sensor. The ISO would be the equivalent of the resistance, or sensitivity, setting of the windmill. If there is a very strong wind (a very bright light), you would likely want the windmill's sensitivity to the air current to be low so that the windmill does not spin way too fast (again, an overexposure). But if the air current is weaker (the light is dimmer), you would want the windmill to be more sensitive to what little air movement there is, so that you can actually complete the 10 revolutions (otherwise, you end up with another underexposure). Thus, for a brighter light, you want a lower ISO number, meaning a lower sensitivity to light. For a dimmer light, a higher ISO with its greater sensitivity to light is generally required.
How do all of these pieces fit together? To maintain an equivalent exposure, if you manipulate one setting, you must manipulate another, though which one is up to you. Say your window is open halfway for ten seconds, with a given windmill sensitivity. You want to open the window all the way, doubling the amount of air coming in at once. To maintain a 10 revolution "proper exposure," you can cut the time the window is open in half, to five seconds, while maintaining the same windmill sensitivity. Or you can leave the time the window is open the same and reduce the windmill sensitivity by half. (You can also reduce the strength of the air current coming through the window, i.e. dim the light source, but that is a topic for another day.) As long as the overall total amount of light hitting the sensor is the same, the exposure will be equivalent. The images may be very different, with vastly different depths of field, etc., but the exposures will be the same. Just remember that to get a proper exposure, you need to hit ten revolutions of the windmill. How you do that is entirely up to you.
Does this mean that you will always want a perfectly exposed image, that exact series of ten revolutions, no more, no less? Not by a long shot. But once you understand how the elements of a proper exposure work, you can then work creatively to craft stunning images that do not fit the strict definition of being "properly exposed." Should you decide that any particular image would have a greater impact by being underexposed, you will understand how to manipulate the elements of our window to stop the windmill after only eight or nine revolutions. Similarly, if an overexposure would give your image that pop you are looking for, you will know how to make that windmill keep spinning right on past ten, not stopping until it reaches eleven or twelve (or seventeen…) revolutions. Mastering these three elements, shutter speed, aperture, and ISO, is truly the key to mastering exposure. And once you master exposure, those creative doors fly wide open. Suddenly you are able to construct amazing images intentionally, and not just chance upon them by accident with no hope of recreating them.
Test yourself. Play with the elements of our window and windmill and try to get equivalent exposures with different settings. Then see if you can create intentional under- and overexposures with multiple settings. Finally, and most importantly, have fun!
May / June Specials
Get 10% off of unframed, 8x12 prints of "Grace in Retreat – Mute Swans" and / or 10x20 prints of "Subtlety of a Sunset – St. Mary Lake" when you order from our specials page. As with all of our unframed prints, these prints are eligible for our No Hassle Returns.
First, the serious side: we are approaching that time of year when nature, when angry, shifts her focus from blizzards and mudslides to violent winds, drenching rains, and unbelievable flooding: hurricane season. Without fail, some of the most arresting photographs to be produced each summer and fall come from areas affected by hurricanes. While we cannot prevent hurricanes, we can prepare for them. The National Oceanic and Atmospheric Association (NOAA) has designated May 25th through May 31st as National Hurricane Preparedness Week. Go to http://www.nhc.noaa.gov/prepare for some great information on hurricanes and cyclones and how to prepare for them. (Perhaps their most poignant advice, especially for photographers, is simple: "The first and most important thing anyone should do when facing a hurricane threat is to use common sense." Sometimes we photographers let our common sense go out the window in our quest for great images. Remember, be safe. You can only create great images if you are alive and well.)
Now the fun side: ever wondered how tropical storms get their names?
* The practice of giving tropical storms women's names began in the late 19th century, became commonplace during World War II, and was made official in 1953.
* It was not until 1978 that men's names were included in the rotation.
* There are three major storm-naming regions in the U.S.: the Atlantic, the Eastern North Pacific, and the Central North Pacific. On the U.S. mainland, we are most familiar with the Atlantic region.
* You may know that a list is prepared prior to each storm season with names in alphabetical order, and as storms appear, they are given names in that order. Did you know, however, that the list is different for each region, that there are only six lists per region (or four, in the case of the Central North Pacific region), and that they are rotated through? In the Atlantic region, for example, the first named storm of 2016 will be "Alex." "Alex" was also the first storm of 2010, and assuming the 2016 version isn't damaging enough to have the name retired, "Alex" will also be the first storm of 2022.
* If a storm causes significant damage to life or property, its name can be retired, to be replaced by another beginning with the same letter. The most names retired in a single year: five, in 2005. Those names? Dennis, Katrina, Rita, Stan, and Wilma. The following year, no names were retired.
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