The Exposure Triangle
This “triangle” is really a balance or formula that gets utilized every time a picture is taken. Like the three sides/angles of a triangle, there are three components to the exposure triangle.
1. ISO—how sensitive your camera is to light
2. Aperture—how open/closed your lens is
3. Shutter speed—how fast/slow your lens opens and closes
ISO: International Organization of Standardization
For film cameras, it was how sensitive a particular film was to light. For a digital camera, it is how sensitive our camera sensor is to light.
- Outdoors in sunshine = ISO 100
- Outdoors in overcast light = ISO 400
- Indoors = ISO 800 or higher
When a film photographer when outside to shoot, she would have to change film to suit the light.With a DSLR, if you want to shoot outside in broad daylight, you would
change your ISO to 100 or 200. If you walked back inside, you would simply change it to 800 or 100.
ISO and Noise
ISO can affect how much “noise” your image has.
Noise is the graininess in digital images. Noise comes from two things:
1. High ISO: the higher the ISO, the more noise
2. Underexposed images: pictures that are not exposed correctly in camera, but later improved in post-processing, will have noise in them, due to the underexposure.
Aperture is how wide the opening of your lens is at the time of the picture.
- A smaller f number (like 1.8) means your lens is wide open, allowing in lots and lots of light.
- A larger f number (like f16) means the lens is more closed down, allowing in much less light.
How does aperture affect your image?
Aperture has two main purposes:
#1 Controls light allowed in through lens
- Large apertures (small f numbers) have a very wide opening to allow in the most light possible.
- Narrow/closed down (large f numbers) have smaller openings, preventing much light from entering in.
#2 Controls the depth of focus when picture is taken
- Wide open (small f numbers) give you a shallow depth of field, meaning just the subject is going to be in focus and most everything else behind it will be blurry.
- Shooting with wide apertures is great for portraits, florals and other subjects you wish to isolate focus on.
- Narrow or closed down apertures (large f numbers) give you a more focused, detailed images. Your subject plus everything around it and behind it will be in focus.
- This is great for landscapes, architectural photography and large groups shots.
Shutter speed is how long your shutter is open.
- Shutter speed will be a fraction like 1/200th of a second.
- In your viewfinder it will just be a number: 200 (for 1/200th) or 1400 for 1/1400th or 20 for 1/20th of a second.
- If you have lots of light, your shutter will be fast.
- If you have low/poor light, your shutter speed will be slow.
How shutter speed affects your images:
- Fast shutter speed can freeze action, like water spraying or jumping kids.
- Slow shutter speed can show motion, like a car driving.
- Slow shutter speed is one of the main contributors to out of focus images.
- If you have a slow shutter speed and you are hand-holding the camera or having a busy subject, you are likely to have some motion blur which will prevent the image from being sharp.
Helpful tip: To ensure sharp pictures, keep your shutter speed at twice the focal length of your lens.
Metering is getting your image properly exposed by balancing the ISO, aperture and shutter speed.
Types of metering:
- Spot – metering is taken from one particular, chosen area (use focal points to pick your spot).
- Center Weighted - bases the exposure on the intensity of the entire frame, but with most of the emphasis on a circular area in the center.
- Matrix or Evaluative – reads the light over the several different spots in image. I almost always use spot metering, but there are times matrix and center weighted work better.
- Landscapes – matrix / Group portraits – center weighted
Want to download the notes? Enjoy here!