A DSLR Camera has many features that allow the photographer to adjust many options of the camera such as focus, shutter speed, aperture, and ISO value (along with many others). DSLR Cameras are designed on the Single-Lens Reflex principle with interchangable lenses. This allows the photographer to change lenses and fully control the effects of each photograph. The camera consists of two parts: the Body and the Lens. The main part of the camera is the Body. This is the part which takes the photo, stores the images and controls the main electronic features of the camera. The Lens is where you set the focusing, Aperture, Zoom and other features. These two make up the camera. One of the main advantages of a DSLR is the capability of changing lenses easily and quickly. You can have many lenses for a single camera or many cameras for a single lens as long as they are compatible with each other. If you buy a DSLR and want to use it to its full potential, I encourage you to turn off the Auto or Program feature and have some fun with capabilities of this system. There are many different modes that you can set on your camera to control different features and settings which effect the composition of the photograph.

A DSLR Camera Body has what's called a "Reflex Mirror" (or flip-up mirror). This mirror sits between the lens and Sensor (CCD or CMOS). This mirror redirects the image up and through a pentaprism to the viewfinder while you're setting up the shot. Once you take the picture, the mirror flips out of the way, opens up the shutter and exposes the sensor to the image coming through the lens. Then the mirror moves back into place. All this happens very fast. There are many features that control how the camera takes the photograph. They are (but not limited to) white balance, focusing points, macro, storage, picture quality and ISO. Some cameras even have the ability to take infrared photos as well. This can create some dramatic effects and record images that are not visible to the human eye.

Sensors and Image Processors

The Sensor is as important as the lens as it's the part of the camera that records the image. They come in different sizes and types depending on the camera you buy. The sensor controls the amount of noise the image has with the ISO settings along with the dynamic range which is the shadows, highlights, colors and sharpness. There are two types of sensors. CCD (Charge-coupled Device) and CMOS (Complementary Metal-Oxide Semiconductor). In today's cameras, the types don't differ in quality much anymore. Allthough, different manufactures do play a large part in their quality. Most DSLR cameras use APS-size sensors which are smaller than 35mm film frame. There is some simple math needed to understand this that relates to focal-length, magnification and lens conversion factors. For example, on a Nikon D200which has an APS-size sensor and a focal-length multiplier of 1.5x, a 50mm lens captures the angle of view that a 75mm lens would on 35mm film (50mm x 1.5 = 75mm). So on this camera body, a 50mm lens acts like a 75mm lens, a 28mm lens acts like a 42mm, a 200mm acts like a 300mm and so on. This is because the APS-size sensor is smaller than 35mm film. If these lenses were put on a Nikon 35mm camera body, they would act as they are stated on the lens. Sport and wildlife photographers like this but landscape and architecture shooters can't get lenses wide enough for their subjects. If this concerns you, then you may want to spend the big bucks and purchase a camera that has a full frame sensor (sensor is the size of 35mm film) such as the Canon EOS 5D.

The lens is a very complex device consisting of many different functions: Zoom, Focus, Aperture and sometimes Vibration Reduction (VR). As I said earlier, one of the main advantages of having a DSLR camera is the ability to change the lens on the fly. If you are at the local arboretum and are photographing flowers and suddenly see wild animals or birds far away, you can switch lenses from your macro lens to a telephoto lens in seconds and zoom in to get the shot you want. The lens is where the Aperture and Focus is performed. This camera can be set to many different settings depending on what you want to control. They are Aperture Priority, Shutter Priority, Manual or Automatic. These settings allow you to change the speed of the shot (shutter speed), the amount of light allowed in along with the focal length and depth of field. Don't worry! Keep reading as I will cover this later. When purchasing your lens, make sure you spend the extra dough and buy the higher end lens with the lens elements coated to correct for chromatic aberration. This is to correct for a defect in the glass that if the lens does not have it can cause reduced sharpness and cause color fringing along high contrast edges. So when purchasing a lens, look for the manufacture codes on the lens. Canon's code is called UD, Nikon and Olympus' code is ED, Sigma uses the code APO and Tamron used LD. It's worth the extra expense especially if you're purchasing a telephoto lens as it is more noticeably when zoomed in.

Aperture:

The Aperture is the lens opening that regulates the amount of light that passes through the lens to the Sensor. The Aperture size is measured in f-numbers (or F-Stop). The lower the f-Stop, the larger the aperture opening is and effectively lets in more light. The larger the f-number, the smaller the opening and less light is passed to the CCD Sensor. The aperture setting not only controls the amount of light, it also controls what is called the Depth of Field which is the what is in focus.

Focusing:

Many DSLR Cameras lens focusing systems use what's called phase detection auto focus. This system speeds up focus process and results in fast focusing. This reduces the focus searching that is typically found in Digicams (point and shoot). Many professional photographers rarely use the auto focus feature when they are in the field. Almost all DSLR cameras today come with auto focus. You can purchase manual focus lenses along with using some older lenses which allows you to control all the aspects of the lens manually

Shutter Speed:

Shutter speed is the amount of time the shutter is held open. It is used to control the ability to stop action (fast) or to blur if wanted (slow).It is scaled in fractions of a second. A shutter speed of 1/1000 is one thousands of a second and is very fast and 1/64 shutter speed is one sixty fourths of a second and is is slower. The shutter speed is also one of the ways to regulate the amount of light that is allowed through to the sensor. Both the aperture and the shutter can control the effective light hitting the sensor but in different ways. The aperture controls it by the size of the opening and the shutter controls it by the time it is open. Each one has a different effect and purpose. The shutter speed only controls how much time the camera has to expose the sensor to available light. The aperture not only controls the amount of light, it also controls the depth of field (focusing depth). The faster the shutter, the lower the aperture number you need. So if you have a fast shutter speed, you need more light controlled by the aperture. This causes the depth of field to be smaller because the aperture opening will be larger. If you use a slow shutter speed, you can have a higher aperture (smaller hole) which will allow a larger depth of field.

Focal Length and Angle of View:

The focal length is the distance measured in millimeters (mm) of the lens. Normal focal length lenses without zoom or wide angle is usually 50mm - 55mm. A telephoto lens has a zoom of 55mm through 500mm and so on. A typical wide angle lens focal lens is 18mm - 35mm. Focal length is usually displayed on the lens and typically defines the lens. The aperture is also displayed on the lens as seen on the right. So if you buy a lens that has a focal length of 18mm - 135mm it will work for wide angle of 18mm to a zoom of 135mm. This determines the lens angle of view and how much the subject will be magnified depending on where the subject is positioned. Another Please note that camera sensor sizes are different in size. Digicams have typically smaller sensors so their focal length will be smaller like 5.8 - 24mm. This would be similar to a 28 - 105mm of a DSLR camera. So the same focal lengths may be expressed using different numeric values depending on the sensor size.

Depth of Field:

The depth of field is basically what you would like to have in focus and what you don't. That said, let's say you wanted to photograph a flower with a butterfly on it but you don't want the truck in the parking lot way behind the flower to be in focus. Well, then you would set a Small F-Stop (large aperture opening) which gives you a shallow depth of field and focus on the flower. The truck would be way out of focus and hopefully unrecognizable. Now, when you have a small F-Stop, you allow more light into the camera so you can (and will need) to use a faster shutter speed. The larger the F-Stop (small aperture opening), the greater depth of field you get. For Example, if you wanted to photograph a family member standing on a dock at the lake and wanted to also have the sunset in focus behind him or her, you would want to have a larger F-Stop (a small aperture) to give you a large depth of field from the subject to infinity. The small aperture would also limit the amount of light coming in so you would also want to force a flash to light up your family member.

Telephoto (Zoom) and Prime Lenses:

A Prime lens is a fixed mm lens that does not zoom like a telephoto lens does. Prime lenses usually have higher quality, less moving parts and it's harder for dust to impregnate the inside of the lens. Telephoto lenses usually change sizes when zooming in and out. This size change has to allow for air to flow in and out of the lens causing small particles of dust inside the lens. If you can afford to carry many lenses (and have the money) then purchase prime lenses. Most of us don't want to carry around all those lenses so try and purchase a high quality zoom lens for every day use. Nikon sells a 28mm - 200mm lens that is fairly small and performs very well. Many amateur photographers usually purchase two lenses. One for wide angle to a small zoom (18mm - 70mm) and then one that picks up where the first left off and goes to 200mm - 300mm. The benefit of a zoom lens is that you can shoot a subject from far away to close up with just a change in zoom. When you buy a zoom lens, make sure you consider it's speed. Yes, I said speed. A good zoom lens is large and has a low f-stop (large Aperture). This is to allow as much light through the camera as possible. This will allow you to use a fast enough shutter to get the shot you want when zoomed all the way in. This speed is defined on the lens by F4, F5.6 but the larger the number, the smaller the aperture is so less light gets in. This will cause you to slow down your shutter speed.