■ No live preview. You can’t preview the image you’re going to take, exactly as the sensor sees it because the sensor can’t create an image until the mirror flips up and out of the way. The LCD of a dSLR is used only for viewing images after the fact, plus for displaying menus and other information.

■ No live histograms. As you’ll learned in later posts, histogram displays are a great way to optimize exposures. If the histogram “chart” is skewed too much in one direction or another, you can add or reduce shutter speed, aperture, or EV value to get the best possible exposure. Non-SLR digital cameras have what are called “live” histograms that show up on the LCD and/or EVF while a shot is being composed, so you can make corrections in real time. That’s not possible with a dSLR for the same reason you can’t get a live preview:The sensor is blind until the moment of exposure.

■ No sneaky surveillance-type shooting. You can connect many digital SLRs to a USB cable and use a special program to control the camera from a distance. However, once again, you’ll be shooting blind. Your control program probably can download your remote photos to your computer after they are shot, but you can’t monitor what the camera sees before taking the picture. If you want to catch a shoplifter in the act, you’re better off with a regular video surveillance camera or even a high-end non-dSLR setup to provide a live feed to your monitor or computer.

■ Shooting blind in dim light or with infrared filters. Here we go again. Because you’re limited to viewing through the dSLR’s optical viewfinder, if light conditions are very dim or you’re using an infrared filter, you have to shoot blind. LCD and EVF viewfinders often have circuitry that boosts the gain under dim conditions, providing you with a fuzzy, sometimes black-and-white image, but one that can still be viewed, even if you’re shooting with an infrared filter that blocks visible light.

■ View on the back panel LCD display. These viewing panels, which operate like miniature laptop display screens, show virtually the exact image seen by the sensor. The LCDs measure roughly 1.6 to 2.5 inches diagonally, and generally display 98 percent or more of the picture view seen by the lens. An LCD may be difficult to view in bright light. Point-and-shoot digital cameras use the LCD display to show the image before the picture is taken, and to review the image after the snapshot has been made. Some of these have no optical viewfinder at all, so the only way to compose a shot is on the LCD. In a dSLR, the back panel LCD is used only for reviewing pictures that have been taken; previewing is not possible.

■ View through an optical viewfinder.Many non-SLR digital cameras have a glass directview system called an optical viewfinder that you can use to frame your photo. Optical viewfinders can be simple window-like devices (with low-end, fixed magnification digital cameras) or more sophisticated systems that zoom in and out to roughly match the view that the sensor sees. The advantage of the optical viewfinder is that you can see the subject at all times (with other systems the view may be blanked out during the exposure). Optical systems may be brighter than electronic viewing, too. A big disadvantage is that an optical viewfinder does not see exactly what the sensor does, so you may end up cutting off someone’s head or otherwise do some unintentional trimming of your subject.

■View through an electronic viewfinder (EVF). The EVF operates like a little television screen inside the digital camera. You can view an image that closely corresponds to what the sensor sees, and is easier to view than the LCD display, but doesn’t have nearly the quality of an SLR viewfinder. The EVF goes blank during exposures, however. Because EVF cameras are usually more compact than dSLRs and can cost less, they have become a popular “SLR-like” alternative to the real thing.

■ View an optical image through the camera lens. Another kind of optical viewfinder is the through-the-lens viewing provided by the SLR camera. With such cameras, an additional component, usually a mirror, reflects light from the taking lens up through an optical system for direct viewing. The mirror reflects virtually all the light up to the viewfinder, except for some illumination that may be siphoned off for use by the automatic exposure and focus mechanisms. The mirror swings out of the way during an exposure to allow the light to reach the sensor instead. Sometimes, a beamsplitting device is used instead. A beamsplitter does what you expect: It splits the beam of light, reflecting part to the viewfinder and allowing the rest of the light to strike the sensor.

As you might guess, because a beamsplitter steals some of the illumination for the viewfinder, neither the sensor nor the viewfinder receives the full intensity of the light. However, such a beamsplitter system does mean that the image needn’t blank out during exposure. An optical viewfinder’s image reflected from the mirror is reversed, of course, so it is bounced around a bit more within the camera to produce an image in the viewfinder window that is oriented properly left to right and vertically.

Some digital cameras use a pentaprism, which is a solid piece of glass and generates the brightest, most accurate image. Others use a pentamirror system, lighter in weight and cheaper to produce, but which gives you an image that is a little less brilliant than that created by a pentaprism. Olympus uses a swinging sideways mirror viewfinder system it calls a TTL Optical Porro Finder on its lower-end dSLRs, which has the advantage of allowing a much squatter profile for the camera cos the big lump of a pentaprism/pentamirror needn’t inhabit the top of the camera. There are several other important aspects of SLR viewfinders that you need to keep in mind:

■ dSLRs provide no LCD preview. Because of the way digital SLRs operate it is not possible to view the image on the back-panel LCD before the photo is taken. That doesn’t seem like much of a problem at first—after all, the optical view is brighter, easier to focus, and often much larger than an LCD preview—until you go to take an infrared photo or other image using a filter that reduces the visibility of the through-the-lens view or obscures it entirely. An EVF camera with an IR filter mounted may still produce a dim, but viewable LCD image which can be used to compose the photo. With an SLR, you’re shooting blind.

■ Vision correction. Although many point-and-shoot digital cameras don’t have diopter correction to allow for near/far sightedness, all digital SLRs have this feature. However, if you have other vision problems that require you to wear glasses while composing photos, make sure your digital camera lets you see the entire image with your eyeglasses pressed up against the viewing window. Sometimes the design of the viewfinder, including rubber bezels around the frame, can limit visibility.

■ Eyepoint. The distance you can move your eye away from the viewfinder and still see all of the image is called the eyepoint, and it’s important to more than just eyeglass wearers, as described above. For example, when shooting sports, you may want to use your other eye to preview the action so you’ll know when your subjects are about to move into the frame. Cameras that allow seeing the full image frame even when the eye isn’t pressed up tightly to the window make it easy to do this. In the past, manufacturers of SLR cameras have even offered “extended eyepoint” accessories for sports photographers and others.

■ Magnification. The relative size of the viewfinder image affects your ability to see all the details in the frame as you compose an image. It’s not something you might think about, but if you compare dSLRs side by side, you’ll see that some provide a larger through-thelens view than others. Bigger is always better, but is likely to cost more, too.

Working with viewfinders will come up again a few times later in this book, but if you remember the basic information presented in this chapter, you’ll understand most of what you need to know.

Indeed, for as long as I’ve been involved with photography, deciding which SLR family to marry into has been an agonizing conclusion. No one prefers to be locked into a product line that won’t do the job, won’t keep pace with technology, or, worse, will go belly-up, leaving owners of a particular vendor’s equipment orphaned, in a sense. A generation ago, film SLR purchasers were committing to cameras produced by companies called Topcon, Miranda, or Yashica. These were fine cameras in their time, but none of them survived to the digital age.

Even among modern digital camera vendors, you’ve important SLR manufacturers that were late to the party (Konica Minolta, for example) and others with now-you-see-it/now-you-don’t products, such as the Contax N Digital, a 6MP digital SLR announced in July, 2000, but later withdrawn from the US market. You can be certain that Konica Minolta is in the digital SLR fray for the long term, but can you be that confident about all the other players in the game?

Digital SLR decision makers often fall into one of four categories:

■ Serious photographers, photo enthusiasts, and professionals who already own lenses and accessories belonging to a particular system, and who need to preserve their investments by choosing, if possible, a digital SLR that is compatible with as much of their existing equipment as possible.

■ Professionals who purchase equipment like carpenters buy routers. They wish something that will do the job and is rugged enough to work reliably despite heavy use and mistreatment. They don’t necessarily care about cost if the gear will do what’s needed, because their organizations or clients are ultimately footing the bill. Compatibility may be a good idea if an organization’s shooters share a pool of specialized equipment, but a pro choosing to switch to a whole new system probably won’t care much if the old stuff has to fall by the
wayside.

■ Amateurs and enthusiast photographers with too much money who feel that the only way they will be able to take decent (or better) pictures is to own the very latest consumerlevel equipment. These are the people who bought the Canon Digital Rebel when it first came out, but sold everything and switched to the Nikon D70 a few months later to gain some additional capabilities. Six months later they were posting questions in newsgroups about whether they should sell everything again and buy a Canon EOS 20D or maybe a Konica Minolta Maxxum 7D.

■ Those who are buying their first dSLR, and either don’t own an existing film SLR, or don’t particularly care about using their old equipment with a new camera. Often, these buyers don’t plan on junking everything and buying into a new system anytime soon, so they are likely to examine all the options and choose the best dSLR system based on as many factors as possible. Indeed, their caution may be why they’ve waited this long to purchase a digital SLR in the first place.