There are, of course, an almost innumerable number of features that can be had in professional digital cameras. Here are the ones you should pay the most attention to.

Does the camera have a viewfinder?
You would be hard pressed to find a digital camera without an LCD display, but not all of them have viewfinders, the classic way to compose pictures, with the camera up to your eye.

For indoor pictures, when there is enough light, composing your shots on the LCD screen works fine. Where it is less useful is outdoors, in bright sunlight. The sunlight can wash out the screen to the point that you can only roughly see what the camera is seeing. A viewfinder lets you see what you are shooting even in bright light. Note that some professional digital cameras offer a viewfinder as an accessory, but this can add significantly to the cost.

What kind of lens does the camera have?
As far as what kind of pictures you can take, nothing is more important than the lens. The lens will allow — or restrict — the kinds of pictures you will be able to take with your camera.

To help you pick a camera, look for three lens characteristics:
Speed — while speed sounds like an odd way to describe a lens, it is photo speak that describes how little light the camera needs to take a good picture. A fast lens can take pictures with very little light, like in a dark restaurant or on the street at night. A slow lens requires sunlight, brightly lit rooms, or the use of a flash in low light. So, depending on where you are expecting to take your pictures, a slow lens might be okay, or you might be looking for the fastest lens you can afford — because faster lenses are more expensive as well.

Zoom lens range — Almost all professional digital cameras come with a zoom lens. Zoom lenses let you frame a picture without moving: you can zoom in and out to get the picture framed just the way you want it. A good zoom can give you a wide angle of view at its widest setting that lets you capture a room full of people, or the Grand Canyon, if you are there. As you zoom in — for what is called a telephoto shot — you narrow the angle of view, for a portrait of one or two people, or for a closer view of Mount Fuji, or any distant object you would like to get a picture of.

Quality — The lens determines the quality of the image recorded by the camera. While the number of megapixels is often thought of as telling you the quality of the picture, that number is meaningless if the lens quality is poor. Unfortunately, there is no simple number to compare the quality of the lenses with to help you pick a camera. In this case, the brand may serve as a guide, or you may need to seek out a review of the specific camera you are interested in. Most digital cameras have lenses optimized for the type of camera — or sensor — they are attached to.

How big is the camera sensor?
Larger sensors typically have larger pixels, a pixel being the smallest piece of information in your photograph. When you talk about megapixels for a camera, that describes the number of pixels you have when you multiply the height times the width.

Larger pixels have one great characteristic: they tend to capture more light than smaller pixels, so they are better at taking pictures in low light. The other characteristic, that photographers and videographers often desire, is that a larger sensor has less depth of field — a measurement of what is in focus for a lens.

Does the camera have scene modes?
Many digital cameras such as the Canon EOS Rebel T3i allow you to select a mode that optimizes the camera’s settings for a particular type of scene. Examples include portrait mode, landscape mode, close-up mode, nighttime mode — all of these help ensure that you are matching the camera capabilities to the subject you are photographing. In addition, some cameras even offer special effect, or art modes. These mode settings are easy ways to improve your photos.
Does the camera support image stablization?
Most professional digital cameras now support some form of image stabilization. This is a feature that allows the camera to compensate for a little shakiness on your part as you take the picture, to improve sharpness in either low-light situations or when you are zoomed out to the telephoto part of the lens.

The most confusing part of this is the many different names manufacturers use for what is essentially the same feature: Vibration Reduction (VR), Optical Image Stabilization (OIS) and, just Image Stabilization.