Anatomy of Canon eos 500d or rebel t1i

In the previous post you saw how you can use the Rebel T1i’s
automatic features for easy snapshot shooting. Before we go on to
learn about its more advanced shooting features, we’re going to
take a tour of the camera and learn its parts. The T1i is a complex
tool, and the better you know its workings, the more easily and
effectively you’ll be able to make it do what you want.

What Is an SLR Anyway?

The Rebel T1i 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 important
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. On 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. Because it’s very simple to engineer and doesn’t take up much space,
a point-and-shoot camera can be made very small.





The 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. 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 2).
When you look through the viewfinder on an SLR, you’re actually looking through
the same lens that is used to expose the image sensor. As in a film camera, the
image sensor in a digital camera sits on the focal plane, a flat area directly behind
the lens. In front of the sensor is the shutter, a mechanical curtain that opens
and closes very quickly when you press the shutter button. The shutter lets you
control how long the sensor gets exposed to light. Obviously, because there’s an
image sensor and a shutter sitting directly behind the lens, you can’t easily get a
clear view through the lens without some work, with the shutter and image sensor
in the way.






Take a look at the profile of your camera and note that the lens is actually sitting
much lower than the viewfinder. If you could take a cross section of your camera,
you would see that the image sensor and shutter are directly behind the lens. In
front of the shutter sits a mirror set at a 45° angle. This mirror bounces the light
from the lens up into a complex optical arrangement called a pentamirror, an array
of mirrors that bounces the light back out through the viewfinder. Thanks to
this system of mirrors, you can see out the lens. Of course, since the mirror sits
between the lens and the focal plane, there’s no way that the image sensor can
see out the lens. This is where the reflex part of “SLR” comes to play.
When you press the camera’s shutter button, the camera flips the mirror up so
that it’s completely out of the way of the focal plane. Then the shutter is opened,
the sensor is exposed, the shutter closes, and then the mirror comes back down.
Part of the distinctive sound of shooting with an SLR is the sound of the mirror
going up and down.

You can actually see the mirror itself any time you take the lens off your camera. It
sits inside the mirror chamber. If you look toward the top of the mirror chamber,
you can see where the light gets bounced up into the pentamirror.
SLRs have many advantages over point-and-shoot cameras, and the fact that you
and the sensor look through a single lens is a very big one. It means that what you
see through the viewfinder is much more accurate than what you typically find
with the optical viewfinder on a point-and-shoot camera. Also, because they’re
larger than point-and-shoot viewfinders, SLR viewfinders are usually much
brighter, clearer, and easier to see.

Of course, on a point-and-shoot camera, when you use the LCD screen as a viewfinder,
you’re looking through the same lens as the sensor. But the optical viewfinder
on an SLR still offers advantages. They’re visible in bright daylight, and as
you’ll see, present you with a view of more of the colors and tones in your image.




Finally, many photographers prefer SLR viewfinders because they like to block
out the rest of the world with the camera so that they can fully concentrate on
the image in the viewfinder. This is much harder to do with the inferior viewfinder
or LCD viewfinder on a point-and-shoot camera.





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