The Canon EOS Digital Rebel XSi/450D Companion

CHAPTER 2

WHAT IS AN SLR ANYWAY?

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What Is an SLR Anyway?

e Rebel XSi is an SLR camera, a term you may have come across when you were

shopping. SLR stands for single lens reflex, and those words tell you some impor-

tant things about how the camera operates.

As the name implies, a single lens reflex camera has only one lens on it. If you’re

wondering why a camera might have two lenses, consider a point-and-shoot

camera. If you look at the front of a lot of point-and-shoot cameras, you’ll see two

lenses, one that is used to expose the image sensor and a separate lens that serves

as a viewfinder. e advantage of this type of arrangement is that it’s very simple

to engineer, and it doesn’t take up much space, so a point-and-shoot camera can

be made very small.

Rangefinder Lens

Main Lens

Unlike an SLR, this point-and-shoot camera has two lenses, one that exposes the

image sensor and another that serves as a viewfinder.

e downside to this setup is that when you look through the viewfinder, you’re

not necessarily seeing the same thing the camera’s image sensor sees. First of all,

you’re not seeing the effects of any filters or lens attachments you might be using,

and, because you’re looking at your scene from a slightly different vantage point,

the cropping you see in your viewfinder might be slightly different from what the

camera actually shoots (this problem is referred to as parallax