Now that you can hold the LCD viewfinder out and see a pretty good--if small--approximation of what your final image will look like, you don't have to perform the previsualization process only in your head (unless you're shooting with an SLR, in which case you have the half-measure of instant playback on the LCD). If you don't do it already, ask yourself when you use your LCD viewfinder how you could improve the picture in front of you, as if it were a final print. Your quick little changes in response to this question will probably make you a better photographer over time.

Five things to look for if you can't see
But what if the thing that's keeping you from getting the shots you want is something a little more basic--plain old visualization? In an ironic twist of fate, I started wearing glasses at about the same time I developed a serious interest in photography. Fortunately for me, I'm hardly the only four-eyed person who gets behind a lens, and the camera industry has made an effort to accommodate photographers and videographers with imperfect vision. Here are some items that can help those of us who don't see 20/20:

Diopter: It adjusts the focus on an eyepiece viewfinder (as opposed to an LCD) so that you can see a clear image in it without your glasses on. It's possible to put a diopter on both optical and electronic viewfinders. While almost all camcorders have them, not all still cameras do. Look for a little sliding or rotating switch next to the eyepiece--that's the diopter control. Many SLRs have optional attachments that augment the built-in diopter by expanding the focusing range even further.

High eyepoint: The eyepoint of an eyepiece viewfinder is the maximum distance you can hold it from your eye and see the image clearly. If you're buying a point-and-shoot camera, you won't find the eyepoint number in the specs. The important thing to know is that eyepoints vary from camera to camera, so you don't have to settle for a viewfinder that you can't get close enough to with your glasses on. If you're buying an SLR, you'll find the eyepoint listed in the specs--20 millimeters is typical in consumer SLRs. Be careful though: not all camera manufacturers measure the eyepoint the same way. Try out the viewfinders on the cameras you're considering, and trust your own judgment about what feels comfortable to you. Some SLRs have optional eyepiece extenders, although they reduce the viewfinder magnification.

Adjustable brightness: Look for a camera that lets you adjust the brightness level of the LCD and/or the EVF. Some let you change the backlight level too. If you're buying an SLR, this will help you only with playback. Some SLRs have interchangeable viewfinder focusing screens so that you can switch in one that's brighter or otherwise easier on the eyes. The Olympus E1 is currently the sole sub-$2,000 digital SLR with this feature.

Comfortable viewfinder magnification: Some viewfinders give you a bigger view of your scene than others. If it's too small, you can end up squinting a lot, and if it's too big, you'll have to move your eye around too much to see the scene you're photographing. Try out different ones and pick a camera that doesn't strain your eye.

LCD view enlarger: Large 2-inch LCDs are becoming more common on digital cameras, and there are even a few models with 2.5-inch screens. But you can do even better than that: Both Hoodman and Statec make LCD hoods that provide 2X magnification. They also improve visibility by shading the LCD from bright light. I haven't tried any of these yet, but I'll let you know when I do.

Your views on viewfinding
A lot of you wrote in response to my column on the relative merits of SLRs and EVF cameras. One of the things the EVF-camera partisans particularly liked about their cameras was the ability to swivel the LCD viewfinder or body to get quick shots at odd angles. That's definitely an element of flexibility that SLRs don't have. EVF fans also liked their cameras' ability to capture video and their long zoom ranges. As one reader noted, if you buy enough lenses for an SLR to match a high-zoom EVF camera in terms of range, you'll end up spending significantly more money.

SLR photographers noted that their cameras have larger sensors, which contribute to images with lower noise levels and generally better image quality, and allow SLRs to provide higher ISO settings. That's an issue I didn't touch on since I was addressing camera operation and not output, but sensor size is definitely a current point of distinction between the two camera types. Of course, if you don't print larger than 8x10 much and don't mind using a flash in low light instead of a high ISO setting, it's probably not a major issue. Better continuous-shooting performance and fast RAW capture were also on the list of features SLR partisans liked.

One reader brought up a good point about EVF-camera performance in low light: Although it's not the case with all EVF cameras, most of the models that are advanced enough to compete with SLRs use an active autofocus system. It works by bouncing an infrared beam off of subjects to calculate focus, so its performance isn't affected by light levels. SLRs, as well as some EVF cameras and many digital point-and-shoot models, use a passive system that detects contrast in order to focus and needs visible light to do it.

Here's my take on this issue: With an active-autofocus EVF camera, the camera can see better than you can in the dark. With an SLR, you can see better than the camera, thanks to the clearer view that an SLR viewfinder provides in dim conditions. You'll have to decide for yourself whether you want the control of manual focus and the responsibility of using it or whether you'd rather rely on a camera that's better equipped to handle the situation. Active autofocus isn't perfect since infrared emitters have a limited range of roughly 20 feet, but once your subject is farther away than that, focusing at infinity will probably do the trick in most cases.