How to Buy (and What's Inside) a Digital SLR Camera

You're ready to step up from a point-and-shoot (or cell phone camera) to a big, old fashioned looking SLR. But what is that exactly? And how does it work? PM dissects one and gives advice and buying tips for every budget.

Single Lens Reflex (SLR) is a complicated term for a complicated machine. It refers to the prism and flip-up "reflex" mirror system that allows users to accurately focus and frame their shots directly through a camera's optics, rather than through a separate viewfinder. Until recently, most SLRs were the province of pros, requiring experience and training to master. But the digital era has created a new, growing class of consumer-grade digital SLR (DSLR) cameras that are easier to learn and use, yet still deliver pro-level photos. These days, the most complicated aspect of DSLR cameras is figuring out which one fits your needs.

1. LCD Display

Like most digital point-and-shoot cameras, digital SLRs have LCD displays--the largest of which are 3 in., diagonally. Older-model DSLRs didn't let you preview your shot using the LCD. Newer cameras with "live view" functionality leave the shutter open and allow light to bypass the reflex mirror. With most of these cameras, users have to choose between framing shots with the LCD or the viewfinder. 

2. Sensor

DSLRs have image sensors that are 10 to 20 times the size of sensors on point-and-shoot cameras. This gives DSLRs far superior light sensitivity, which is arguably more important to overall image quality than megapixels. Most DSLR cameras can vibrate the sensor to remove dust particles that often enter the camera when changing lenses. 

3. Memory

CompactFlash memory cards used to be the data storage capacity kings, but the far more popular Secure Digital High-Capacity (SDHC) format now has cards with up to 32 GB, and newer DSLRs are trending toward it. 

4. Battery

Long battery life is critical for DSLRs, which have lots of motors and powerful flashes. Most DSLR batteries are good for a full day's shooting. If you require more, we suggest you buy an extra. 

5. Flash

Consumer digital SLRs come with a pop-up flash. Advanced users will want to take advantage of the hot shoe, which allows the use of more sophisticated, synchronized--flash accessories. 

6. Shutter

DSLRs are known as fast-shooting machines, with shutter lag measured in tenths or hundredths of a second and burst modes from 2.5 to 10 frames per second. 

7. Lens

When you buy a DSLR, you're buying part of a larger system. Most DSLRs can be purchased as a kit that includes an all-purpose zoom lens. But manufacturers also sell dozens of specialized lenses that can transform the performance of your camera. These days, lenses pack almost as much technology as the camera itself. 

+ Autofocus

It's powered by the camera battery, but all the gears and motors are built into the lens. The lens interfaces have changed over the years, so many new cameras won't work with old autofocus lenses. 

+ Image Stabilization

Many modern lenses come with a mechanical system that counteracts camera shake and reduces blur. On some lenses, it costs extra--but it's worth it.