Understanding the relationship between ISO, shutter speed and aperture is key to effective, creative photography. If you can get a handle on how they interact, you will finally free yourself from your on-camera flash & AUTO setting.

Today's DSLR cameras have Manual settings to allow you to control these 3 ingredients of creative exposure. DSLR’s are more user friendly and you may have to dig a little through the menus of your point-n-shoot but they’re in there…

So why is there a picture of an eyeball above? Well, for the purposes of this tutorial your eye is the best, most efficient camera ever invented! And it has an ISO setting, aperture setting and shutter speed.  If you can understand your eye as a camera, you will be able to understand how these three elements effect your exposure.

For our analogy: ISO is your retina, your eyelids are the shutter and your iris is the aperture.

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First off, some definitions are in order to understand what each of these elements do to exposure…

ISO: This refers to “film speed” or sensitivity to light.. (this is your retina- the back wall of your eye where light lands after it passes through your pupil). It’s also referred to as ASA across the pond. No difference, same thing… If I refer to film in this discussion I’m referring to your digital camera’s sensor unless of course you are a film shooter and for that you get an extra point for effort! A low ISO, say 100, will give a lot of detail but needs a good amount of light. A high ISO, say 3200, needs a lot less light BUT you sacrifice detail and end up with grain and “noise”. So a good rule of thumb for ISO is to always shoot at the lowest possible ISO for optimum detail. How do you know what the lowest possible ISO setting is? Well, stay with me, we’re going to put it all together, I promise!… View the examples below to see how an image is affected by ISO settings:

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Shutter speed: This is how fast the camera’s shutter stays open during the exposure. (these are your eyelids). Try this: go outside in the sunshine and close your eyes. Now open and shut your eyes as fast as you can. Congratulations, you just took a picture with the most advanced camera known to man… Since it’s nice & bright outside I bet you saw a lot of the scene even though you blinked really fast. In other words, you didn’t need to have your eyes open for very long at all to let in a lot of light. (A very fast shutter speed will also freeze motion. Hence, sports photographers require a very fast shutter to freeze the motion of the athletes). Now go outside at night and do the same thing. I bet you didn’t see much detail in the scene. Now try it again, at night, but leave your eyes open for say, 10 seconds. With your eyes (shutter) open for this long, your retina (camera sensor) is able to absorb a lot more light and detail in the scene. However, with your shutter open for this long, anything moving will be blurred (can you say tripod?! with a long shutter exposure a STEADY camera is essential). With a steady camera and a long shutter exposure, you won’t have blur from camera shake but if anything in the picture your taking moves, it will blur.. We can use this to our creative advantage though, such as when taking photographs of moving water.

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Aperture: This is your iris. In photography we call this your “f-stop”. In bright sun, your pupils are very tiny, or constricted (a small aperture) and at night your pupils are dilated (large aperture) to let in the appropriate amount of light. If you dilated your pupils (aperture opening) in bright sun, way too much light would be hitting your retina (camera sensor) and your image would be too bright or “blown out”. Likewise, if your pupils were constricted at night, not enough light would be hitting your retina and your image would be too dark. So in dim light a large aperture is helpful in letting more light into your lens onto your sensor. Another function of aperture is “depth of field”, or how much of your scene is in focus. Did you ever see an image, say a portrait for example, where the persons face is in sharp focus but everything behind them is blurred out? This is because a large aperture was used, f/2.8 for example, giving a “shallow” depth of field. Or how about a landscape scene where everything is in focus from foreground to background? This is because a small aperture was used, say f/16 or f/22, giving a wide depth of field. See examples below to illustrate how the size of your aperture affects depth of field:

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OK, so how do we put this all together so you can turn off your flash, put your camera to Manual and start producing more creative images?. Well, we must discuss the all important relationship between these three factors and how one is dependent on the other. As you’ve probably surmised already, all of this has to do with AVAILABLE LIGHT. Remember, you have turned your flash OFF! Creativity begins with shutting off that on-camera flash that will wash out your image and make them scream, “snapshot!” We don’t want snapshots, we want more professional, creative images, right?! I will however mention that “fill flash” (yes you have that on your camera) can enhance, not over-power an image when your subject has a lot of light behind them like the sun.

Our camera needs light to capture an image. We have 3 controls to vary the amount of light that enters the lens. You guessed it, ISO, Aperture & Shutter speed. Changing the settings of any one of these will cause more or less light to enter your lens. To make things easier if you're new to all of this I’m going to have you choose a different setting on your camera other than Manual… If you check the settings on your camera you’ll see there is an “Aperture Priority” setting (Av or A) and a “Shutter Priority” setting (Tv or S). Put your camera to Aperture Priority mode and then TURN OFF YOUR FLASH. Most cameras have a flash button (lightning bolt symbol) that will toggle you through different flash settings, red eye flash, fill flash, etc. You want the one that shuts it off: usually the lightning bolt with a circle around it and a line through it. Also, set your ISO to 100.

In Aperture Priority mode, you set the aperture and the camera will automatically select the shutter speed that will give you a proper exposure (not too bright, not too dark). Here’s a good rule of thumb for choosing the right settings: When hand-holding your camera, you want your shutter speed to be faster than the focal length of the lens.  In other words, if your lens has a 50mm focal length, you would want your shutter speed set to 1/60th of a second. This will help avoid blurry images due to camera shake. Chances are, you won't be able to set the shutter speed exact due to your cameras settings.  Just make sure it's set to a faster setting than the focal length of your lens. So, if we’re in Aperture Priority mode and we control the aperture setting, how do we know what setting to choose? Good question! Here’s the answer: It depends on how much of your image you want to be in focus, or how much “depth of field” you want. See the aperture examples above again. If you want only the object you are focusing on to be in focus and everything in front of and behind it to be blurred out, you’ll want to choose a wide or large aperture, say f/2.8. This is a great effect for portraits! Now, if you are taking a picture of a scene that you want more “depth-of-field” or more of the foreground and background to remain in focus, you’ll want to choose a smaller aperture, say f/16.

Remember I stressed the importance of the relationship of our 3 elements of exposure earlier? Well here is where it starts to matter.. As you DECREASE the size of your aperture (a smaller & smaller hole for the light to get through), the LONGER the shutter will need to remain open to get a proper exposure.

Here’s a scenario: You’re standing on the edge of a beautiful lake with a bright red canoe on the shore in front of you. You think, “great photo op” and pull out your camera. Now if your camera is on AUTO, your image will look like anyone else’s so you decide to get creative and put your camera into Av mode. You want everything in focus from the canoe in front of you all the way into the distant edge of the lake to get that beautiful fall foliage in, so you choose an aperture of f/16 for a wide depth of field. However, the sun’s going down and there’s not a lot of available light so the camera is choosing a very slow shutter speed, 1/5 sec for example, to let enough light into the lens for proper exposure… You just happened to be walking by and didn’t bring your tripod so you’re going to hand-hold your camera. Also, you just had a lot of coffee and your hands are kind of shaky.. As we learned earlier, a shutter speed this slow while hand-holding your camera will surely produce camera shake and blur your image.

What to do, what to do? Well we have a couple of options.. You could put your camera on a tripod. Oh, that’s right, you don’t have one.. Then is there a rock, stump, dock, etc. that you can place your camera on so it doesn’t move during the exposure? Can you lean against a tree and stay rock solid while taking the image? That’s one way to solve the camera shake issue.. By the way if you are going to do this, put your camera on its self-timer setting so you don’t jar the camera while pressing the shutter button! There’s another way to solve this… What about that other element of exposure, ISO!? Your camera’s sensor will get more and more sensitive to light as you raise the ISO number. So by going from ISO 100 to ISO 800 the camera will choose a faster shutter speed and make it easier to hand-hold your camera. Be careful though! As we learned, the higher you go with your ISO the more noise and grain your image will have! (yuck)

What else could you do? You could change your mind about the depth of field and choose a very shallow depth of field so the red canoe is in focus and the distant Fall foliage will be blurry but still add some nice color to the image. In my opinion, this would be a more artistic way to go and make better use of the low ambient light. So you decide to do this and change your aperture to f/2.8 (or as low as your camera will go) and now with much more light coming in through that big hole of an aperture, the camera is going to choose a faster shutter speed allowing you to hand-hold that camera and get a crisp shot! No AUTO setting!!! No Flash!!! You just created an artistic exposure! Doesn’t that feel good! Wait till your friends see this one…

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In Summary: If you got through all of that I’m proud of you! It means you’re hungry to learn and now you have a new understanding of how to control light and depth of field!

3 ways to control available light that are all dependent on one another:

• ISO: by increasing the ISO setting, your camera’s sensor gets more sensitive to light allowing you to shoot in dim or dark places without a flash. The trade off is noise & grain in your image as the ISO goes up. Remember the rule of thumb: Always shoot at the lowest possible ISO for maximum clarity and detail. Rather, adjust your aperture and/or shutter speed and keep the ISO low! More expensive DSLR cameras will handle high ISO settings very well with minimal noise. Point-n-shoot cameras are not so forgiving… You get what you pay for!

• Shutter speed: The faster the shutter speed, the less light that comes into the camera. You’ll compensate by using a wider aperture or raising your ISO. A fast shutter speed is needed to freeze motion, like sports. If shooting moving subjects like sports your shutter speed should be at least 1/125 sec or preferably higher if you really want to freeze the action. A slow shutter speed will allow more light into the camera but your image will be affected by camera shake and anything moving in the frame will be blurry… With your camera on a tripod and a slow shutter speed, you can capture artistic shots like a smooth waterfall or a city/street scene with colored, snaking lines from headlights & taillights…

• Aperture: The smaller the aperture (larger the f-stop number), the less light it allows into the camera. You’ll compensate by using a slower shutter speed or raising your ISO. Also, the smaller the aperture, the more depth of field you will have.

So when taking your image, you’ll need to decide first what is most important for the shot. Are you shooting a portrait? Fast action/sports? A city scene at night? A bride & groom walking down the aisle in a dimly lit church that does not allow flash? If you are taking a portrait and want a wide aperture so just your subject is in focus, you should go with Aperture Priority, choose a wide aperture and let the camera set the shutter speed. If the shutter speed is too slow you could raise your ISO, for example. If you are shooting fast action, you should go with Shutter Priority, set a shutter speed of at least 1/125 sec and let the camera set the aperture. If the aperture is too wide (say the camera sets it at f/2.8 but you want more depth of field than that, you could decrease the shutter speed a little or raise the ISO.

Another setting on your camera that will help you in the beginning is P Mode, or “Program AE Mode”. AE stands for auto exposure. In P Mode the camera will automatically set the Aperture and Shutter speed. You can still adjust your ISO but using this setting can still produce artistic images, you just don’t have as much control.. It is different from Auto setting in that it allows you to control your ISO and will not automatically fire the flash. If you’ve learned anything here, stay away from AUTO for creative images!

For ultimate control, choose M, or Manual setting. On Manual, you control everything and the camera just obeys! This will give you the most amount of creative control and once you master it you won’t go back!

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So here’s a final example (albeit a very simple example) of how to get creative with basically anything.. While typing this I turned around to look for something to shoot and saw my guitar. To give you an idea of using a different setting other than AUTO, I shot the neck of the guitar in front of my lighted globe.

The first image shows what AUTO setting will produce. Very “snap-shotty” and not very creative… I then put my camera to Aperture Priority Mode and set my aperture at a very wide f/1.8 because I wanted to isolate the neck in focus and have a very shallow depth of field. When I did this, my camera chose a shutter speed of 1/8 sec- (the lighting was pretty dim in my room). That’s too slow, and I could get easily get camera shake. I wanted to get the shutter speed up to at least 1/60 sec but I really wanted to keep my wide aperture of f/1.8… So I raised my ISO from 100 to 800 and Voila! my shutter speed read 1/60 sec. Perfect! The second image shows a more artistic or creative version of the scene without the harsh light of the flash and the shadow it cast. The blurred out, nondescript  background and ambient light (no flash) in the second image brings  more attention to the subject and makes for a more creative shot.

Now it’s time for you to grab your camera and start getting creative! Digital photography requires no film!!! Shoot away, once you’ve paid for your camera, it’s free!!! Enjoy yourself and good luck with your artistic images!!

On a side note, in order to help you determine initial settings, the following rule can be used.  It's called the "Sunny 16 Rule".  The Sunny 16 Rule establishes relative camera settings.

If your camera is set to an ISO of 100, set your shutter speed to 1/100 sec.  If the ISO is set to 200, set your shutter speed to 1/200 sec. (most cameras do not have a 1/200 second shutter speed setting; you must use the next closest one which is probably 1/250 sec.).  Then use the following chart:

Once you have the initial settings for proper exposure, you can adjust your shutter speed or aperture to achieve the desired affect for your photograph.  Keep in mind that once you have your settings, any adjustment to one setting will require an adjustment to the other.  For example, you have your camera set to f/16 and your shutter speed set to 1/100.  You decide that you want to stop the motion of the subject so you change your shutter speed setting to 1/500.  Since you've changed to shutter speed setting two stops (1/100 to 1/250 to 1/500), you must also change your aperture two stops.  Keep in mind how the change has affected the camera.  Since you sped up the shutter speed, you're letting in less light.  You must now adjust your aperture setting to let in more light so you would change it from f/16 to f/8 (f/16 to f/11 to f/8).  It's a good idea to memorize the f/stop differences but keep in mind that they may be listed or set in your camera as full-stops, 1/2-stops, or 1/3-stops.

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