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Digital Photography Basics

What is digital photography? Simply put, photography is the process of capturing images focused through a lens to be stored electronically on a computer for further image enhancement. Unlike film photography, which the photographer develops in a dark room, digital photographs develop instantly into a digital computer file (.RAW, .JPG, or both).  Before you begin snapping pictures for your image slideshow, it's important to think about how you will compose your shots using the basic principles of photography: exposure triangle, white balance, focal length, and image composition.

Exposure Triangle

The exposure triangle is comprised of three variables: ISO, aperture, and shutter speed. Each plays a significant role in how much, how long, and how intense light passes through the image sensor.   

Note: Consult with the DSLR camera instruction manual to learn its capabilities because image sizes vary based on camera type and brand. The general rule for an image sensor is the larger the size, the better the image.  


ISO is the light sensitivity to a camera's digital image sensor.  ISO can be set to high or low values at 100, 200, 400, 800, and 1600. Newer DSLR camera models with larger image sensors have been able to set ISO values as high as 3200 or 6400, and still produce good quality images. But, Beware!  The general rule is the lower the ISO, the sharper the image, and the higher the ISO, the noisier the image.   

two pictures side by side that illustrate the sharpness of an image snapped with low vs high iso.      Image Credit: Ashutosh Jaiswal from Pexels                                                                                                                                                                                                    

A low ISO value is ideal for outdoor shooting where natural light is present. In outdoor settings, less sensitivity is needed to light the subject. The result is sharp images with no noise.  On the contrary, a High ISO is ideal for indoor shooting where artificial light or very little light is available in the area.

Setting the ISO value to a high number makes the image sensor more sensitive to light, but may produce noise in overexposed settings. 



Aperture is the size of the opening in a camera lens through which light travels to the image sensor. The opening is characterized as F-stops.  As a general rule, the smaller the F-stop number, the larger the opening and the shallower the depth of field.



Depth of field demonstrates how much the subject is in focus. In images with shallow depth of field, the point of focus is sharp, and the foreground or background is blurred. As illustrated above, low f-stops produce a shallow depth of field and high f-stops, narrow depth of field. 


   Image Credit: Eve Ellis, SMDC

As shown in the image above, the first image used a low f-stop number, which produced a blurred background with a sharp point of focus. The opposite image used a high f-stop, which created an image with a deep depth of field. As you will see in the second image, more of the area around the point of focus is in focus with little to no background blur.  

Simplified - How aperture works  

LOW F-STOP = More light/shallow depth of field (little to no background blur)

HIGH F-STOP = Less light/deep depth of field (background blur)


Shutter speed is measured in seconds as the amount of time your shutter is open. The settings range between 1/1000th(fast) - 1/2(slow) of a second. Photographers use faster shutter speeds to capture fast action like sports and moving objects. Fast shutter speed settings freeze motion, whereas slower shutter speeds capture motion blur. 

image of windmill showing     Image Credit: MikeRun / CC BY-SA (Creative Commons)  

The focal length of the camera lens affects shutter speed settings. As a rule of thumb, for sharper images, the focal length that one uses should either match or exceed the shutter speed. For example, if you are using a 50mm lens, the shutter speed should be no less than 1/50th of a second. Consider this rule as a starting point for shutter speed settings. Depending on how fast the subject is moving, the shutter speed may need to be set at a faster rate.                                              






Changing the settings for the ISO, Aperture, and Shutter speed is accomplished in the camera mode.  Professional DSLR cameras use several manual modes, the advanced modes that are offered depends significantly on the camera. However, most DSLR cameras share common camera modes. 


Image Credit: Althepal at English Wikipedia / CC BY-SA  

(P) Program Mode: Automatically set your exposure by choosing the Aperture and shutter speed based on the lighting conditions.
(S) or (TV) Shutter Priority: Photographer can control the shutter speed settings to achieve maximum exposure.
(A) or (AV) Aperture Priority: The photographer controls the aperture settings to achieve maximum exposure.
(M) Manual Mode: Photographer has full control of making adjustments to the ISO, aperture, and shutter speed.
DSLR cameras also come with automatic modes with presets for image exposure: Auto, Action, Portrait, Night portrait, landscape, and macro.  

Rule of Thumb (Manual Mode)
  • If the image is too dark adjust exposure triangle in the following order: Slow shutter speed, lower aperture, raise ISO
  • If the image is too bright, adjust in the following order: lower ISO, raise shutter speed, increase the aperture.

White Balance

In addition to making decisions about the exposure triangle, photographers need to consider white balance. White balance measures the color temperature of the light source via the camera’s settings. Auto white balance (a feature present in most DSLR camera configurations) looks at the colors in a frame of view and tries to determine the overall temperature of what the scene is and tell the camera to match those colors to give the image a natural look.  

Color temperature is measured in Kelvins (K). Most cameras have the following white balance presets: 

If the colors from the presets do not measure up, you can add a custom white balance by taking a picture of a sheet of white paper or card in the subject area that you plan to shoot in. Photographers can also use the Kelvin scale to create white balance.

Focal Length


The focal length is the optical distance (measured in millimeters) from which light rays converge between the lens to the camera image sensor.  The focal length is measured in millimeters (ex., 35mm, 50mm, or 100mm). Zoom lenses state the range (minimum and maximum) of focal length. (ex. 18 – 55mm or 75-300mm).  
The focal length of a lens tells the photographer two things: 

  1. The angle of view is how much of the scene will be captured.
  2. Magnification is how large the subject will be within the angle of view.

As described in the previous section (shutter speed), the focal length is also used as a guide for appropriate settings for snapping sharp or creative images with blurred motion.  

The field of view depends on the sensor size, which is not one size fits all. Several sensor sizes range from a 35mm full-frame (high-end DSLRs) to 28mm low or midrange sensors. The sensor size matters in photography because it determines how much light is used to create an image and how much area will be covered in the field of view.  

LONGER FOCAL LENGTH = Narrow angle of view/high magnification) SHORTER FOCAL LENGTH = Wide angle of view/low magnification. 

Interchangeable cameras lenses offered at the Student Multimedia Design Center for a short term loan. 

stand alone 60 mm macro lens

Canon EF-S 60mm F/2.8 Macro USM Lens

stand alone 100 mm macro lens

Canon EF 100mm F/2.8 Macro Lens


 stand alone 75 - 100mm zoom lens

Canon EF 75 -300mm F/4.0 - 5.6  Zoom Lens