Photography is about capturing light from the scene and getting the proper exposure. To evaluate and control the exposure, you need to assess the Scene Luminance (Light Intensity) which is the amount of light available in the scene being photographed. Then use the exposure triangle to determine the correct camera settings
In this tutorial, I will explain in detail what the exposure triangle is and how to use it to get proper exposure.
- What is exposure?
Exposure is the amount of light that reaches your camera’s sensor when a picture is taken, creating the visual data necessary to form a photo. Camera exposure is the overall brightness or darkness of a photograph.
The more you expose the camera sensor to light, the lighter your photo will be overexposed (the photograph loses highlight details and the bright parts become blown out or washed out.
The less light, the darker your photo will be underexposed (the photograph loses shadow details and the dark parts are almost all black.
- What is the Exposure Triangle?
The exposure triangle is a visual identification of the main elements that affect the exposure in a photograph: aperture , shutter speed , and ISO , and the way these elements are related. If you know how to control or adjust these elements, taking well-exposed photos will not be a problem for you. Let us look at each element closely and understand how they can help you achieve the right exposure.
Aperture refers to the size of the circular hole in the lens that lets in light. The aperture is physically located inside the lens, as shown in the below diagram.
This aperture is regulated by a diaphragm made of overlapping blades that can be adjusted to vary the size of the opening through which light passes. The photo below shows a typical diaphragm with 9 blades.
The bigger the hole, the more light that reaches the sensor. In fact, each time you double the area of that opening, you double the amount of light or increase the exposure by one stop. On the other hand, if you half the area of the opening, you half the amount of light hitting the sensor. In addition, you guessed it; that will decrease the exposure by one stop.
Aperture has a big impact on the depth of field. A Large aperture (remember it’s a smaller number) will decrease the depth of field while a small aperture (larger numbers) will give you a larger depth of field. A detailed discussion about controlling your depth of field is given in my post << How to Control DOF of Your Photos – Shallow Depth of Field vs Deep Depth of Field >>.
In addition, the aperture has an effect on the way that out-of-focus areas, particularly highlights, are rendered. This effect is referred to as the lens’s Bokeh. Good and nice-looking bokeh is generally having highlights that are rounded rather than having straight sides, and also the edges of these highlights should be soft and not haloed or hard-edged.
The best results are usually seen when the diaphragm has many blades (9 being typical) or more, that produce a nearly rounded edge (to create an almost spherical opening).