Digital Photography

Over the last week or so, I’ve been nagging you to take your camera out of Full Auto mode so that you can control aperture (f-stop), shutter speed, and ISO to suit your creative vision. But precisely how much control you have over those three major exposure settings depends on your camera, so dig yours out and let’s do a little inventory of your options.

Start by locating your camera’s exposure mode dial or switch. On a digital SLR, it usually looks something like the picture here, which shows a dial from a Canon Digital Rebel model. Compact cameras often sport a smaller version of the same dial, although in some cases you may have to dig into the camera’s menus to uncover all your options.

Here’s a list of the most common modes:

• Full Auto: Usually represented by the word Auto, a rectangle (as here) or little camera icon, this one leaves all exposure settings up to the camera. 
• Automatic Scene modes: These are the modes represented by the little pictographs. They’re designed to automatically select aperture and shutter speeds that work best for different types of shots. For example, in Portrait mode, the camera chooses a low f-stop, which reduces depth of field so that the background will be in soft focus; in Landscape mode, the camera dials in a high f-stop to keep both background and foreground sharp. And Sports mode gives you a fast shutter speed to help you capture moving subjects. The range of scene modes varies widely from camera to camera, so you’ll need to check your manual to find out what options you have. The names given to the scene-mode feature vary, too; for example, Nikon uses the term ”Digital Vari-Program modes”; Canon goes with ”Image Zone” modes.
• Programmed auto (P): In this mode, the camera selects the aperture and shutter speed it thinks will work best, just as in full auto mode. But typically, you can then choose from a few other combinations that will deliver the same exposure, so you get some — but not much — control over f-stop and shutter speed. Some manufacturers refer to this mode as flexible programmed auto.
• Shutter-priority autoexposure (S or Tv): In this mode, you set the shutter speed, and the camera selects the correct aperture setting for you. (The Tv stands for time value; remember, the shutter speed controls the exposure time.) It’s great when you’re shooting action and shutter speed is critical — your priority, if you will.
• Aperture-priority autoexposure (A or Av): In this mode, you select the f-stop, and the camera then chooses the right shutter speed to properly expose the picture. (The Av stands for aperture value.) This mode is perfect for shooting portraits, landscapes, and other still subjects because it enables you to manipulate depth of field through the f-stop setting.
• Auto Depth of Field (A-DEP): This one’s found on some Canon cameras. It analyzes the scene and then tries to select an aperture setting that will produce the depth of field needed to keep all major objects in sharp focus. However, a good exposure is favored over f-stop, so in some lighting conditions, the camera may not select a setting that achieves the depth-of-field goal.
• Manual (M): In manual mode, you dial in both aperture and shutter speed. The camera does offer some assistance, however, by presenting an exposure meter or some other guide to let you know whether it thinks your exposure settings are off the mark.

You may have noticed that my descriptions don’t say anything about ISO. That’s because how much you can control ISO in each mode depends on the camera. So again — regretfully — I must refer you to your manual for that bit of detail.

The other important thing to know is that on most cameras, the Auto and Scene modes usually limit your photographic choices beyond exposure. Usually, you can’t tweak color or control flash, for example. And  as with A-DEP mode, whether the camera can choose an appropriate f-stop or shutter speed for your subject depends on the lighting conditions. For example, in a dimly lit gym, the camera probably won’t be able to select a shutter speed fast enough to stop action even in Sports mode.

As for Programmed Auto and A-Dep, well, their main benefit is that they won’t allow you to choose settings that under- or overexpose your picture. But because you can always check exposure in your monitor, I suggest that you bypass those two modes in favor of aperture-priority and shutter-priority autoexposure, if your camera offers those modes. Then you can dial in a specific f-stop (with aperture-priority mode) or shutter speed (with shutter-priority mode), depending on your creative point of view.

Manual mode? Well, when you get proficient at manipulating exposure, you’ll probably want to shift into that mode because it’s the only way you can control both f-stop and shutter speed. But when you’re just starting to understand exposure, the “priority” modes offer the best combination of control and autoexposure support. In upcoming posts, I’ll tell you a bit more about using these two modes to your best advantage.

Exposure

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