How is the camera lens like the human eye?

Digital SLR Camera Explained

Digital
Single
Lens
Reflex
Camera

Light enters the lens through an opening called an Aperture.  The Shutter is a trap door in front of a sensor that records the light. A system of mirrors allows you to see exactly what your lens sees.

Basics of Exposure

Sunny 16 Rule

Exposure Outcomes

Underexposure: Not enough light reaches the sensor (the resulting image is too dark and lacks white values)
  • ​Photo Log symbol to use in the Outcome column: <
Correct Exposure: Just enough light reaches the sensor (the resulting image has all values from white to black represented)
  • ​​Photo Log symbol to use in the Outcome column: !
Overexposure: Too much light reaches the sensor (the resulting image is too light and lacks black values)
  • ​​Photo Log symbol to use in the Outcome column: >​

Camera Displays

LCD Panel (Liquid Crystal Display)
Moving Clockwise from top left to bottom left
White Balance (indicates type of light source)
​Shutter Speed (represents 1/x in seconds)
Aperture (listed in f-stops)
Frame Counter (shots remaining)
Drive Mode (single, continuous, or timer)
Light Meter (indicates exposure level)
Battery Level (must charge here at school!)
​Lenses
Focus Mode (AF = automatic, MF = manual)
Focal Length (wide 18-55mm, fixed 50mm, zoom 75-300mm)
Menu Options
Image Quality (always set to large!)
Format (erases the memory card)

Metering

In-camera light metering works reasonably well with most subjects, in most lighting situations. However, there are tricky scenes that will baffle most meters — and snow is a classic example. The camera will automatically try to reproduce it as gray, by underexposing anywhere up to about two stops to correct for what it sees as a too-bright subject. This is exactly why many photographers will find their snow photos to be muddy and underexposed.

Exposure Compensation

Exposure Compensation (EC) lets you deliberately lighten or darken your exposures. You can vary the amount of compensation, anywhere from plus or minus 1/3 of a stop (often, a barely noticeable difference) up to plus/minus three full stops, which will significantly change most images. Using “plus” compensation adds light, so it always deliberately lightens images you’re about to take.

Bracketing

In some more challenging lighting conditions, it is hard to know exactly how to expose your images for the best possible results.  What many photographers do in these situations is bracket their shots.  Bracketing means shooting three identical photos of the same scene with different levels of exposure from light to dark.

Steps for Bracketing:
  • Set the camera mode to manual, ISO 400, and compose the scene.
  • Determine the recommended exposure using the light meter (this reflects 18% grey for an average value range).
  • To bracket, you must change either the aperture or the shutter speed, but not both.  Keep one setting consistent.  In this example, the aperture remained the same and the shutter speed changed from fast to slow.  You can also vary the exposure by adjusting the aperture size from small to large.
  • It is just important that you use three settings in a row (whether you are bracketing the shutter speed or bracketing the aperture), while the middle frame remains as the light meter's recommended exposure.  
  • Open the three images side by side to view the distinct differences in values and determine which once contains the best detail quality and dynamic range.

Histogram

Reading a histogram properly helps photographers determine the appropriate exposure for the scene, and whether they are at risk of severe under- or overexposure.
But, if your histogram shows portions of the graph that appear to get cut off on the far right, that means portions of your scene are severely overexposing to the point that detail may be washed out. This is a warning that your exposure should be adjusted. If you see this, try applying minus Exposure Compensation, until you see that no part of your histogram is cut off at the right edge.

White Balance

White Balance settings adjust the camera for the overall color character of the light source you are shooting in, so images can have a neutral rendition that properly renders colors in the scene. Many Canon EOS photographers let the camera read light and adjust this automatically, with Auto White Balance (AWB). There are also fixed, pre-set white balance settings, such as Daylight, Cloudy, Shade, and Tungsten.