The Exposure Triangle and How it Affects Your Photos


Getting a new DSLR can be quite an overwhelming experience for a new photographer. All the knobs and buttons seem to do a thousand different things (and they do), but the dirty secret of photography is that at its core, knowledge of the exposure triangle is what will make your new DSLR really sing. If you know how the exposure triangle works, then you essentially know the basics of photography for beginners and you can build your skills with the manual functions of your camera from that solid basis.

The biggest benefit of having an advanced DSLR is that they allow manual control over most elements of the photographic process in terms of what's happening in the camera. But having that control means that it is of great benefit if you know what elements you need to control and what they do. Let's take a look at the three absolute essentials that make up the exposure triangle – ISO, Shutter Speed and Aperture.

ISO – In film cameras, the ISO refers to how sensitive the film is to light. In a DSLR the same concept applies, but it refers to the sensor setting instead of film. Basically, the lower the ISO number, then the less sensitive it is to light. If you are out photographing things in the bright midday sun, then you will probably want to use the lowest setting available (probably ISO 100 or 200). Conversely if you are photographing poorly lit scenes then higher ISO settings are in order. Just remember than the higher ISO settings often bring the problem of digital noise (unwanted speckles and spots in your images). Usually the top end DSLRs are better at handling noise problems at higher ISO settings.

Shutter Speed – This one is fairly self-explanatory. Shutter speed simply refers to the amount of time that the shutter on the camera opens for when you take a shot. A shorter shutter speed will result in less light hitting the sensor and will have the effect of “freezing” motion. A longer shutter speed will allow more light to hit the sensor and any movement in the scene will appear blurred in the direction it was moving (“motion blur”) which can often be a desirable effect depending on what you are trying to achieve. Each shutter speed setting doubles (or halves) the speed compared to the next setting. Don't forget to check out our beginner's guide to shutter speed priority mode on your camera.
Motion blur by themonnie, on Flickr

Aperture – This refers to the size of the opening in the lens that lets light hit the sensor. Wider apertures obviously allow more light in and narrower allow less light in. The size of the opening is measured as f/1.4, f/2.8, f/4, f/5.6,f/8, f/16, f/22 etc (commonly referred to as “f stops”). The small the number, the larger the opening and each “stop” up from there effectively halves the size of the opening (and thus the amount of light entering the camera). Aperture also allows you to control depth of field. Also, check out our beginner's guide to aperture priority mode on your camera.

How Does That Work in Practice?

The three elements of the exposure triangle interact together. For example, reducing the shutter speed by a stop (increased light) and narrowing the aperture by a stop (decreased light) will result in an identical exposure. However it may result in motion blur (due to decreased shutter speed) or deeper depth of field (due to narrower aperture).

Together, ISO, Shutter Speed and Aperture are collectively referred to as the exposure triangle. This is probably one of the most important technical concepts you can know in photography and it's worth sitting down to learn (and standing up to practice) if you'd like to know how to use that shiny new DSLR (or any other camera, for that matter) to its potential.

About Author

Rob is the founder of Light Stalking. His love for photography pushed him into building this fantastic place, and you can get to know him better here.

Tell us how to override these hi-tech point and shoot cameras so that those of us who like experiment can override the auto systems.

Have you manual override on you camera, that is you can set ISO, aperature and shutter speed manually. you then get to play with depth of field etc.

I’ve been really trying to wrap my brain around everything I’ve read with luck. I’m a visual learner. You kept it very simple & I get it! Thanks

I pass these items on to friends of mine who are just starting out. They are very easy to follow and it stops them harassing me every 10 minutes with such things like “Are ISO speeds the same as film speeds then”. Very useful.

Hi Rob, I have been following Light Stalking fr a while and learning all the time.
Can I ask a question? I can move the focus spot around the viewfinder, is this also the metering spot?

In the part about aperture ( f/1.4, f/2.8, f/4, f/5.6,f/8, f/16, f/22) it is strange that f/1, f/2 and f/11 are left out with no plausible reason.

The f-stop or f-number is actually the ratio of the focal length of the lens divided by the diameter of its aperture. With that in mind you can see why f/1 and f/2, or anything in that range, would be rare. A 50mm focal length f/1 lens would be 50mm in diameter (almost 2″). An f/1 250mm zoom lens would be 10″ in diameter!

As for f/11, it is a common lens speed for deep sky telescopes 6″ in diameter and larger. Also, I remember a time when it was a common f-stop to use on manual lenses.

Even if we only get a small part right, then that something less to learn in the future. Thanks Rob…. always a good read. regards Peter B

The problem is not understanding these concepts, it’s that no one is giving examples of them working together which was briefly mentioned here. Give
example scenario’s of how to shoot and compensate the triangle plus and minus according to the time, light, subject and purpose.

The key is your camera’s light meter. It should be 0 or as close as possible. If it is reading -1 and you already are at f/1.8 then you can either slow down your shutter or raise your ISO by 1 stop. Study about metering and the triangle will make sense.

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