Shoot Anything with 3 Steps - Shutter, Aperture, and ISO (2)

September 09, 2019  •  Leave a Comment

How to Use Shutter, Aperture, and ISO to Get Great Photos.

Today's cameras have made taking great looking photos available to everyone. When my grandson was only two, he was able to hold a pocket camera, set to the automatic mode and capture delightful shots from his perspective. The reason it all works so well, is the tiny computer built into today’s cameras.

In automatic mode, we turn over the technical side of photography to the computer. This lets us concentrate on the people, places, and ambiance of the moment. I always recommend using the automatic mode when the conditions are suitable. But often the camera’s computer lets me down. The subject or the entire scene is blurred. Have you ever tried to take a photograph of a high school basketball game only to leave with a series of streaks where the players should be?


How do I know when I need to take more control? And what settings need changing?

If you want to learn when and how to take control when the auto mode lets you down, first understand a few simple facts about the camera and how it works. With the exception of a few artistic photographers that want to step outside the lines, all photos need to be correctly exposed. This simply means that for each shot, there is only one correct amount of light that should reach the sensor. It doesn't matter if it is early morning with its subtle dim colors, high noon with bright skies overhead, or indoors at your cousin's wedding. Get the correct amount of light to hit the sensor and the photo will look fine.

In the past, photographers had to use hand-held exposure meters to read the light and then set the camera to achieve the correct exposure. Our cameras have the light meter built in and the internal computer will adjust the settings for us. So why do some of our photos look fine while others resemble a Jackson Pollock abstract painting? It all about the way the camera settings are made.

It's all about the settings.

Although there is only one correct exposure, the way that the camera is set will affect how the photo will look. This is because there is not just one device, but three that all work together to adjust the end result. Shutters can be set to fast or slow. Apertures can be wide or narrow. And the ISO can change the sensitivity of the sensor to the light that records the image.

Think of it like trying to fill a child's inflatable wading pool by carrying water from the kitchen sink. You make choices that can affect how the job gets done. The pool, full of water is like the photo having the correct exposure. The size of the bucket is like the sensor's ISO setting, the larger the bucket, the fewer trips you need to make. The higher the ISO, the more sensitive the sensor is to the light and so the less time it needs to be exposed to it. Simply put, a high ISO equals a big bucket and the job gets done faster. If the ISO is set low, more time will be needed to get enough light onto the sensor. Just as if a small bucket is used, it will take more time to get enough water to the pool. But we're not done yet.

At the kitchen sink we have other choices. We could turn the faucet just a bit and a thin trickle of water would fall into the bucket. Or with the faucet wide open, the water flow would be far greater and the bucket would fill much faster. This is like the camera’s aperture. Like the iris in our eye that opens or closes as we look at scenes with different brightness, the camera has an iris inside the lens. If it is set to a small opening, or aperture, a little light gets through. At a large aperture, much more light heads for the sensor.

The last choice we can make at the sink is how long to keep the faucet open. If we let it run for a minute, the bucket will fill to the top. But if we prefer to carry less water and stop after twenty seconds, the bucket is less than half full. Less water means more trips. Our camera has a way to time the amount of light getting to the sensor; just as we can control how long to keep the faucet open. It is the shutter, a set of curtains in front of the sensor that open for whatever length of time we wish. A long opening means that more light gets through. Set the shutter to a short or fast setting and we restrict the light. Just like timing how long the faucet is open.

By now you have probably noticed that each of these choices affects each other. If we use a large bucket but only fill it for fifteen seconds, it is the same as using a small bucket. If we only open the faucet half way, we can still fill the bucket but we must wait longer. If we want to get the pool full as fast as possible, we will use the largest bucket, open the faucet wide, and keep it open until the bucket is full. We will make fewer trips, but have to carry more water each time. If our back pain is of more concern, we could use a smaller bucket and make more trips with less water each time. Or we could use the large bucket but only fill it half way... same result.

How it all comes together.

Now here's where it all comes together to give you the control you want to capture that awesome dunk shot at the basketball game. Let's imagine that the neighbor's dog likes to run over and bite your leg. If we carry more water with each trip, we lessen the chance that the dog will see us. We have three ways to control how fast it will take to get the pool full quickly and avoid the dog. We could use a large bucket, wide opening at the faucet, or keep the water running longer each time to insure the bucket gets full. If we want to stop, or freeze the fast action at the basketball game, we also need to speed up the time it takes to get the correct amount of light to the camera sensor. Like the faucet, we can open the lens to a wide aperture. This lets the greatest amount light pass toward the shutter. Therefore it needs to be open for less time, just like the faucet needs less time to fill the bucket if it is wide open. And if that isn’t enough, we can increase the ISO, making the sensor capture more light just like using a larger bucket. This will reduce the number of trips thus avoiding the dog and, for our photo, blurry players.

So why, you may ask, don't the camera manufactures lock the settings to the fastest shutter speed so our basketball photos are always fine? In fact, you can get just a camera. Those cheap, disposable box cameras are preset for outdoor photos in daylight. But they have their limits. We couldn't take photos of cousin Alice's wedding inside the dark church. And forget about sunsets or the family in front of Cinderella's Castle after dark. You see, there are many kinds of photos that we want to take. Each requires different choices and we need the controls to allow us to get the desired result. Yes, we could add a flash to provide more light, but that too has its limits. Ever take a photo from the back of the church, only to have the last five rows to show? Or try taking a shot of the Rolling Stones concert at Madison Square Garden with a flash. You will have an awesome photo of section 1B, rows 95 to 102... But Mick will be obscured in the vast black background. Flash just isn't able to go very far.

So here are the simple choices that you can make to get your photos to show what you were experiencing:

  • If you need to freeze action, choose a fast shutter speed like 500 or 1000. That will stop more blurring. If the action is still too fast, increase the ISO to 400, 800, or 1600.

  • If you have lots of light but your landscapes are fuzzy in the foreground or background, close the aperture to 11, 16, or 22. That will increase the depth of focus, but the shutter speed will have to slow to get the correct exposure. That's why you want lots of light. If you try a small aperture at dawn, you will need a tripod.

  • If you are taking a head and shoulder portrait and you want the distracting background to get out of focus, use a large aperture, like 3.5 or 4. The shutter will speed up to compensate.

How to do it.

Now here is what you have been waiting for. How do I set the camera to control the shutter speed, aperture, or ISO? Well the trick is in knowing the secret codes on your camera’s dial. The one that's normally set to AUTO, look for a setting marked "Sp", or "Tv", or just "S". These stand for "Shutter Priority" mode. This is the setting that gives you control over the shutter speed. When the camera is set here, you can increase or decrease the shutter speed by using the control knob or, on some cameras the left and right arrow buttons. On the screen you will notice that the shutter speed will change as you use the controls. Shutter speeds are large numbers like 125, 500, or 2000. Apertures are shown in small numbers such as 3.5, 5.6, 8, or 11. Once you choose the shutter speed, the camera will lock it and you will see the aperture number's move to compensate as the light changes.

Suppose you wish to lock in the aperture to control the depth of focus and let the camera choose the correct shutter speed. Then look for a setting on the mode dial marked "Ap", "Av", or "A". These stand for "Aperture Priority" mode. Use small numbers like 3.5 or 4 to give a narrow focus range for close-up portraits or flowers, and high numbers like 8 or 11 for everything to be clear from your feet to the mountains in the background.

Finally let's talk a bit about ISO. This is perhaps the least understood setting under your control. As I mentioned earlier, ISO controls the sensitivity of the camera’s sensor. In the days of film, we choose the film based on its ISO. For outdoor shots in bright sunlight, we used ISO 25 film. To photograph a museum where flash was restricted, we choose ISO 400. And for a little of both, we would buy an ISO 100 film. With digital cameras, these choices, and many more are built in.

So use the same rules. For bright light use ISO 100. For indoors use ISO 400. But if you need more sensitivity, to allow for the shutter speed to be faster and freeze the basketball jump shot, use ISO 800 or 1600. The camera will automatically take the new setting into consideration. Then freeze the action by setting the mode dial to shutter priority and use a high shutter speed.

General Rule: Use Auto Mode whenever conditions allow.

Like most things in life there are often undesirable side effects. High ISO settings introduce a problem called noise that can make your photos look sandy or spotted. So keep the ISO at 100 when you don't need the extra sensitivity for low light or indoor action shots. High aperture numbers can force the shutter speed to be too low to hand-hold the camera without getting shaky results. High shutter speeds will force the camera to set the widest aperture and even that might not allow enough light to enter through the lens. So as a general rule, use the "AUTO" setting whenever the conditions are normal with bright light and little motion.

So try these new options. Get that mode dial off of AUTO and shoot some indoor, action, or close-up photos. Learn how to choose which mode is right for the conditions. And take lots of practice shots. They don't cost anything but your time, and you might enjoy controlling the camera instead of having to live with the decisions the AUTO mode makes.



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I've completed a few photo tours of our great country and lived to write about it.   To read about my misadventures along the way, please visit my blog Travels into Wild America. 

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