The “Exposure Triangle” is a concept that is central to good photography and anyone wanting to take photography more seriously should be aware of its implications. It essentially represents the relationship between three key factors that, when combined, give you your final image, or “exposure”. These are the three key elements that YOU can control to decide what image you end up with, namely – your shutter speed, your aperture and your ISO sensitivity. Let’s look at them one by one.
The Shutter Speed is a time-based value, a measure of time that is, determining how long your camera will let in light onto your sensor, or film. The shutter can be described as a door that opens up for a specified period of time, and then closes again once that time is up. Obviously, the longer the door stays open, the more light can come in. It stands to reason then, that the longer the shutter stays open, the brighter (i.e. whiter) the image will look.
Next is the Aperture: which is a hole with a variable-diameter inside a lens construction. The diameter (or width) of the hole can be increased or decreased by the photographer. Once again, the wider the hole is, the more light will pass through making the image brighter (i.e. whiter). Aperture values are generally written in “f” notation, for example f/2.8 or f/16. The smaller the f-number, the wider the aperture (diameter) is, and hence the more light can pass.
Finally, we have ISO sensitivity which is the equivalent of film speed, for those of you familiar with film or still using it. The premise is simple here – the more sensitive to light that your sensor or film is, the faster it will go from black to white under the same amount of light. Therefore, if I take two images and in my second attempt I use a higher ISO or film speed, whilst allowing the same amount of light in, the second image would still look brighter (i.e. whiter). What the higher sensitivity does is to “detect” light more easily, thus allowing you to end up with brighter images even when the light levels are low.
So far, so good. By understanding and controlling these factors, photographers can obtain “correct exposures” which in brief can be described as being an exposure that is neither too dark nor too bright when compared to the subject being photographed. Is knowing the above enough, however? Doesn’t automatic-mode on your camera result in such images? Well – sometimes, automatic mode has your back and knowing the above becomes superfluous. However, there is more to shutter speed, aperture and ISO than meets the eye – each comes with a trade-off, and finding the correct balance between the benefits and costs of each of these factors is just as critical.
More on that in my next post though! For now, it’s already a step in the right direction to familiarise with the above terms! See you next time!