How the Camera Works

( both film and digital )

The Basics

Just like a film camera, the digital camera has a series of lenses that focus light to create an image of a scene. But instead of focusing this light onto a piece of film, it focuses it onto a semiconductor a (device that records light electronically) that has a sensor to convert light into electrical charges. A computer then breaks this electronic information down into digital data. All the fun and interesting features of digital cameras come as a direct result of this process.

Inside the Camera

Film Camera Digital Camera

Lens• At its simplest, a lens is just a curved piece of

glass or plastic. Its job is to take the beams of light bouncing off of an object and redirect them so they come together to form a real image -- an image that looks just like the scene in front of the lens.

Lens

Light Radiated energy, which forms the portion of the spectrum visible to the human eye.

ISO• The letters ISO on your digital camera settings

refer to the film speed. Even though your camera is most likely not film at all, but rather digital, the ISO setting still does the same function as older film cameras. ISO determines how sensitive the image sensor is to light.

• If you set your digital camera to a low ISO, for example 100, the resulting photograph will be better quality than one set at 1600. The higher the ISO the more grainy the photo will look.

ISO Continued • The lower the ISO number, the slower the speed. • The higher the ISO number, for example 1600,

the faster the speed. • Use an ISO of 100 or 200 when taking

photographs outside in sunny conditions.• If the sky is overcast or it is evening time, then

use an ISO within the range of 400 to 800.• Night time or in cases of low light you might need

to set your digital camera ISO to 1600. If you don't then your photo will appear too dark if at all.

Digital Camera Exposure and Focus

Just as with film, a digital camera has to control the amount of light that reaches the sensor. The two components it uses to do this, the aperture and shutter speed, are also present on conventional cameras.

ExposureThe amount of light that falls on a film or a sensor. In a camera, the length of time the shutter is open, and the size of the opening through which the light passes determine exposure.

ApertureThe adjustable opening in a camera lens used to control the amount of light reaching the sensor in a digital camera or film in a conventional camera. The size of this hole is called the f-stop it is also referred to as aperture value.

F-stopHere is a list of F-stops:

F 16 (small aperture so less light is let in)F 11 F 8 F 5.6 F 4 F 2.8 F 2F 1.4 (large aperture so more light is let in)

More about the ApertureA larger aperture opening (lower f-stop) will have a blurred background. This works well for portraits. Small aperture opening (higher f-stop) will make the foreground and background be equal in focus.

Depth of Field (DOF)

The distance between the farthest and nearest points which are in focus. "Depth-of-field" can also be used to describe the zone of acceptable sharpness before and behind a given focused subject. DOF varies according to numerous factors such as lens focal length, aperture, shooting distance, etc.

DOF and Aperture

Lower f-stop = decreased DOFHigher f-stop = increased DOF

Shallow DOF Great DOF

Shutter

For a film camera, it is mechanical device that controls the amount of time light is allowed to pass through the aperture to expose the film.Unlike film, the light sensor in a digital camera can be reset electronically, so digital cameras have a digital shutter rather than a mechanical shutter.

More about the Shutter

• A fast shutter speed can freeze the motion of a fast moving subject, and a slow moving shutter speed can blur the subject to give the impression of motion.

Shutter Speeds1/1000 (Fast) 1/5001/2501/1251/601/301/151/81/41/21 (Slow)

What these numbers mean is how long the shutter speed is open. For example, 1/500 the shutter is open for 1/500 of a second. If it is just a number, 1” then it mean it shutter is open for 1” second.

Shutter, Aperture, and DOF

In order to have the correct amount of light you must understand the basics.What would you need to change if you want the DOF to be increased?Aperture = f 2 = Large openingShutter = 1/1000 = FastDOF = Shallow

Digital Camera Resolution

• The amount of detail that the camera can capture is called the resolution, and it is measured in pixels. The more pixels a camera has, the more detail it can capture and the larger pictures can be without becoming blurry or "grainy." Some typical resolutions include:

• 640x480 - This is the low end on most "real" cameras. This resolution is ideal for e-mailing pictures or posting pictures on a Web site.

• 1216x912 - This is a "megapixel" image size -- 1,109,000 total pixels -- good for printing pictures.

• 1600x1200 - This is a 2.1-megapixel camera. You can print a 4x5 inch print taken at this resolution with the same quality that you would get from a photo lab.

• 2240x1680 - Found on 4 megapixel cameras -- this allows even larger printed photos, with good quality for prints up to 16x20 inches.

• 4064x2704 - Digital cameras with 11.1 megapixels takes pictures at this resolution. At this setting, you can create 13.5x9 inch prints with no loss of picture quality.

The size of an image taken at different resolutions