Feeling Thirsty? Let’s Talk About Exposure...

Last week, I got a message from a reader that gave me the idea for this week’s article. They wanted to know some of the basic functions on their camera before an upcoming trip. I was glad to hear that they wanted to know more. I'm excited that they may be able to trust themselves to stray away from the ‘Auto’ setting (as setting a camera to Auto cedes many decisions from the photographer to an algorithm. With a little knowledge - you can slowly wrest some of that control back from your camera.

Some of the simplest things to regain control over are also some of the most powerful in determining the final ‘look’ or exposure of your photograph. So let’s break it down.

An simple way to understand exposure is to think about a cup of water. Now, please stay with me!

Let’s say a full cup of water is an ‘ideally’ exposed photograph (that is to say, not ‘too dark’ nor ‘too bright’) and you, as the photographer choose how you want to fill that cup. An exposure, technically speaking, will be influenced by 4 powerful factors: Shutter speed, Aperture, ISO, White Balance; and, all of these factors need to be considered together, in order to fill the cup. However, the method you choose will often depend on the end result you want to achieve.


Shutter Speed:

Do you want to fill the cup quickly or slowly? How long can you hold (or want to hold) the cup under the running faucet? A 60th of a second? 10 mins? There are a range of possibilities, but you need to consider how quickly the water is flowing and how big your cup is. In photographic terms, this allows you to either freeze the action or to give the impression of movement. The classic example is photographing a waterfall. In the picture to the left, we have a really quick shutter (a 500th of a second) and the picture on the right, a very shutter (a 15th of a second). Ultimately, the exposures are equivalent (we’re collecting the same amount of water/light in our cup/sensor) but for different lengths of time.


Do you want to let the water trickle into the cup or turn the water on full-blast? Again, consider the size of the cup, and how long you’ll be filling it for to determine how quickly you allow the water/light to flow. In photographic terms, the aperture allows you to control the depth-of-field. If you allow a deluge of light into you exposure, you’ll get a blurred background. If you restrict the light to a trickle, the entire frame will be sharp. Remember: The smaller the aperture number - the larger the aperture (e.g. f1.2 is a larger aperture than f16).

Below, on the left is an example of the shallow depth-of-field that is achieved with a relatively large aperture. Notice that only the middle-ground is in focus while the fore-ground and back-ground are blurred. On the right is the same example, but with a deep depth-of-field achieved with a small aperture. Everything in the photo is in focus.


How big of a cup are you filling? Is it a stock pot or a thimble? You need to consider how long and how powerful the water-flow is before you decide how big of a cup you need (or vice versa!) In photographic terms you are controlling how sensitive to light you want your sensor to be. A low ISO (the stock pot) isn’t very sensitive and will take a large amount of light (water) to fill up. A high ISO (the thimble) is very sensitive and will fill up without much light. So in low-light situations (unless you have a tripod and/or non-ambient light) you would generally choose a high-ISO and in bright-light you would generally choose a low-ISO.


White Balance:

Are you filling your cup with cold, warm or hot water? As you can probably tell, this factor is a little bit different than the others (and for those of you shooting in a RAW file format, something you have the luxury of considering after-the-fact, if you wish). White Balance will affect the ‘look’ of your exposure just as much as the factors above. White Balance will determine if the colours in your photo will be warm, neutral or cold. But it works independently of the above 3 factors. After all, you can fill a 500mL cup, with a blast of water for 5 seconds - but that none of that is impacted by whether the water is hot or cold. However, in the end a cup of hot water is completely different than a cup of cold water.

The images above illustrate the impact that white balance can have on an image. Here we have from left to right, (Top Row): In Camera Auto, Photoshop Auto, Daylight Preset, Cloud Preset, Shade Preset, (Bottom Row) Tungsten Preset, Florescent PreSet, Flash Preset and 2 custom white balances that I've set in the extreme to illustrate the variation that can be achieved.


I hope this gives you enough insight and confidence to turn off the ‘Auto’ setting on your camera (at least once in awhile). When you see the results that taking full-control can achieve, I promise you’ll never return to ceding your choices to a computer.

If you have any questions, comments or suggestions for future articles, please leave them in the comment below.

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Feature Photograph of the Week - Emerald Reflection 4

Emerald Lake, BC (inside Yoho National Park) is one of the most magical places in all of Canada. As part of Canada 150, here is the third photo (fourth in the series) of Emerald Lake.

Emerald Lake, BC (inside Yoho National Park) is one of the most magical places in all of Canada. As part of Canada 150, here is the third photo (fourth in the series) of Emerald Lake.