The confident shopper's guide to digital cameras
From the Print Edition:
Tom Selleck, Nov/Dec 2007
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Smaller image sensors have another interesting side effect when it comes to digital SLRs (D-SLRs): an apparent magnification occurs when you put a lens for a 35mm camera on a digital camera. With nearly all D-SLRs, the image appears at least a third closer than it would on a 35mm film camera—with some, it looks twice as close. It's not that you're getting actually more magnification, it's that the sensor is only seeing part of the light the lens is throwing down the barrel. The lens illuminates an area the size of a 35mm frame, but your digital sensor is sitting right in the middle, only grabbing the center part of the image. If what you're after is greater telephoto power, this works to your advantage. The challenge, though, is finding a D-SLR lens that can take wide-angle shots. When putting together a camera/lens combination, consider how the magnification factor affects the lens range (information that is always included in the camera description). On a film camera, for example, a 28mm lens is considered a moderate wide-angle, but mounted on the Olympus E-510, it's the equivalent of a 56mm, which isn't a wide-angle lens at all.
There's less math involved when shopping for a compact digital, since you're only dealing with the lens that's permanently attached, and manufacturers routinely publish the zoom lens range equivalent for 35mm film cameras. In film camera terms, a lens around 18mm gives you a fish-eye effect, roughly 28mm to 35mm is considered wide- angle, 50mm to 75mm is "normal" (i.e., your picture shows about what you'd see with your naked eye) and 100mm and higher are close-up and telephoto lenses that magnify distant objects.
Another figure to consider is lens speed, the term photographers use to define a lens's ability to gather light efficiently. A lens rated at f1.8 is faster than an f2.8 lens, which means it will let you take pictures in lower light without a flash. The variation in lens speed among digital cameras ordinarily isn't that wide, but if you have two models with similar telephoto ranges and features and you're looking for another decision-making parameter, now you have one.
To a politician, shaking hands is an occupational requirement. To a photographer, hands that shake are the enemy. Some cameras combat jitter with an image stabilization system that automatically compensates for your movement and keeps the image blur-free. The most common approach is called optical image stabilization—optical elements within the lens redirect light when you shake to keep the internal light-hitting- sensor mechanism steady. Another effective approach, mechanical image stabilization, moves the image sensor itself to compensate for your stability-challenged camera work. For a compact camera, it's pretty much a toss-up between the two technologies. For a digital SLR, there's a benefit to using mechanical image stabilization—it works inside the camera itself, so you'll reap the benefit even when you change lenses.
A Sensitive Question
The option to take photos without a flash is always nice. You can be less intrusive, get natural-looking lighting and avoid the shrieks of small children whose eyes have been hit with a blast of photons. Along with lens speed, another weapon in your low-light photography arsenal is the maximum light sensitivity of the image sensor. This is measured as an ISO rating—the higher the number, the less light required to take a picture. In the past two years digital cameras have boosted ISOs—today you'll find many large and small cameras with ISOs up to 1600, and some reaching 3200 (though this is ordinarily achieved at less than the camera's full resolution). Shooting at the highest ISOs does come at an image-quality cost: the higher you go, the more grain and noise you'll see in the image. On the other hand, that extra head room does come in handy. Shooting with a digital SLR at night on a Tokyo Bay harbor cruise last year, I pushed the ISO setting to 1600 and got several worthwhile shots—a little extra grain really didn't detract from the scenic images, though portraits shot under the same conditions would have looked awful.
Screens and Viewfinders
Every digital camera has an LCD screen, which is great for seeing a photo moments after you've pressed the shutter. When you line up a shot in the first place, however, the LCD may not be the best option.
Nearly any compact camera will let you compose a shot using the LCD display held at arm's length. Some have an additional eye-level viewfinder, some don't, and it's worth considering the benefits of that viewfinder before writing it off as unimportant. In the glare of a bright sunny day, an LCD screen is often difficult to see clearly. Some screens do a better job than others, but the option to hold the camera up to your eye and frame a shot eliminates the problem entirely. Holding the viewfinder to your eye also helps steady the camera, and you save battery power when the LCD is off.
A key benefit for SLR shooters is that the optical viewfinder — instead approximating the frame—peers through the lens that will actually feed light to the sensor. A handful of SLRs now offer a system that also lets you shoot using the rear LCD panel, which is great for over-the-head shots or holding the camera at other odd angles, buslows down camera response time when taking action shots.
If the cameras are so smart today, why do we need manual controls at all? Simple. The camera can read lighting conditions, but it can't read your mind and figure out what you think is important in the picture you're taking. Is the fast-moving car in the scene the vital bit, or is it the woman standing by the side of the road? Do you want to keep the beautiful trees and meadow sharp or just focus on your daughter as she holds a daisy in the foreground and let the distracting background go fuzzy?
The simplest way to tell the camera what you want out of a shot is to choose a scene mode. Most consumer-oriented cameras come with a variety of predetermined settings based on the subject you're shooting—portraits, landscapes, night scenes, fast-action sports, extreme close-ups and so on. Some cameras have literally dozens, which allows for special situations such as shooting at a beach or taking pictures of fireworks.
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