Lesson 3: Using a DSLR Camera

Lesson 3: Controlling Exposure with a DSLR Camera

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Lenses and Aperture

Say you were inspired by the birdwatching pictures from Amherst College's Book & Plow Farm, and you decide to buy a zoom lens. You find a 300mm lens with f/4 as the widest aperture setting for $950. Then, you click over to look at a 300mm lens with f/2.8 as the widest aperture. It costs over $5,800.

"What!" you say to yourself, "the focal length and thus the magnification of both lenses are the same! How can one lousy aperture stop cost six times as much money?" 

The answer is that in photography all stops are exponential. That means f/2.8 lets in twice as much light as f/4 does. If an indigo bunting lands on your bird feeder at dusk, then that extra stop could be the difference between a picture you can use and a picture you can't. 


Light meters are useful. They instantaneously compare real world light to the current camera settings, and then recommend letting in more light, less light or doing nothing.

Light meters are not, however, smart. They have no idea what matters in a picture. In fact, light meters simply average out the intensity of reflected light to a specific midtone value– 18% grey, if you're curious. While light meters usually get the exposure right, they can sometimes go astray by misunderstanding what part of the scene the photographer meant to gauge.

For example, a sunny day with snow on the ground is very bright. Unchecked, your camera's light meter will try to make the snow 18% grey, and so the whole picture will be underexposed. The moral here is that you will sometimes need to manually override your light meter's suggestion to achieve a good exposure.

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Shutter Speed

Setting shutter speed can be a practical choice based on how much light is available, but it can also serve as a creative storytelling choice. For example, shutter speeds less than 1/30th of a second can create motion blur, while shutter speeds above 1/250th of a second freeze the action in a way our own brain does not.

The slowest shutter speed you can hand-hold on a DSLR without getting motion blur is approximately 1/15th of a second. The exact boundry where involuntary motion blur begins will fluctuate depending on the focal length of your lens and whether or not your subject is in motion. 

Depth of Field

Understanding depth of field benefits your visual storytelling and your visual composition. No technique is better at guiding the viewer to what's important in the frame. 

Three factors control depth of field. Low aperture numbers, longer zoom lenses and getting closer to the subject create a shallower depth of field. High aperture numbers, wide angle lenses and moving farther away from the subject create a wider depth of field. 

Adjusting ISO

As promised, here is a thorough explanation of the origin of the ISO acronym.

For most of us, it's enough to know that ISO is a scale measuring how light sensitive your camera will be. Lower ISOs are less light sensitive, but make for a higher quality image. Higher ISOs are more light sensitive, but the image quality is lower, and can become grainy with high numbers like ISO 3200. ISO 400 and 800 are standard ISO settings to use.

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Choosing a Camera Mode

Whew! After all those scales and stops, you might be tempted to leave your camera in auto mode. But it's truly worth your time to practice in the manual modes of your DSLR until you're comfortable using them.

Learning to control exposure and depth of field isn't some useless abstraction. These techniques are frequently the difference between a successful visual story and a picture that doesn't quite work. 


Using an External Flash

Plenty of online resources can guide you in using an external flash and in more complicated studio lighting. New camera models also do a fine job of handling low light, so you can often avoid a flash altogether.

Remember that no matter what technical choices you make, the heart of visual journalism is the story the picture tells, not the technical choices you make. So get out there with your DSLR and start finding good stories!

Adobe Photoshop Basics

Like Kleenex or Jet Ski, Adobe Photoshop has become so ubiquitious that its brand name has today become a generic verb. But be careful, because that verb implies a type of manipulation unethical in visual journalism. The NPPA Code of Ethics demands that digital editing "maintain the integrity of the photographic images' content and context." 

Want to learn more? You can find YouTube tutorials for everything you want to do in Photoshop, or you can download the free open-source program GIMP, which offers Photoshop-like functionality.

Next Step

Now it's your turn.

Log into Moodle to complete the Lesson 2 exercises.