My three part series on the exposure triangle, like all good things, must come to an end. Today, I close the loop and take you through ISO, what it is and how it affects the way you shoot.
In my last post, I explain the exposure triangle using the analogy of a room, with a big window letting in lots of light, with someone sitting on the bed inside the room, looking out into the light. Where the size of the window represents the aperture, and the speed at which you might close the curtains representing the shutter speed, and finally the strength of a pair of sunglasses that you might wear representing the ISO.
In short, ISO (and the ISO level) represents the level of sensitivity that your camera sensor will have to the available light. Where the measurement of aperture is somewhat confusing, and counter intuitive, here the measurement of ISO makes much more sense. A low ISO number (and ISO number of 100 for example) represents a very low sensitivity to light, with an increasingly high number (and ISO of 3200) making your camera very sensitive to the light around it. Make sense, right?
Here’s another way of thinking about ISO: Imagine that the image sensor in your camera is covered in a sticky surface. When your image sensor is sensitive to light, that sticky surface will be incredibly sticky, and all the available light possible will stick to the sensor. When your sensor is less sensitive to light, that sticky surface will be more selective and only catch some of the available light, making it less sensitive to the light particles.
Life on Safari in the bush is absolutely magical. As I mentioned before, the early morning and evening light is beautiful, and with the wildlife as your subjects, you can rarely go wrong. However, these periods of soft light can often provide us with difficult lighting conditions as photographers. Here’s where knowing and understanding your ISO levels come into play in quite a big way. Remember that ISO, aperture and shutter speed, and the adjustments thereof, all have an effect on each other. Remember that by increasing the opening through which light travels (aperture), and by subjecting your sensor to light for a long or short period of time (shutter speed) while varying the sensitivity of your sensor to the light will yield all sorts of varied types of images. So, as the light rises or fades, remember to keep your ISO in mind, and adjust it according to the available light. Just as you would add or remove a pair of sunglasses when the light gets brighter or fades, so too must you adjust your ISO.
Finally, the last thing you need to be wary of when shooting in alternating lighting conditions is that the higher your ISO goes, the more propensity for ‘noise’ (or grain in your image) there is. That ‘sticky surface’ will collect all of the light, and do its best to gather as much of it as possible to expose your image correctly, but in doing so will create that grain that most photographers will not thank you for. As with anything, it’s the balance of the three exposure parameters that will yield the best results, and the practice that you put in out in the field that will develop that feel for when to adjust your sensitivity to the light.
As always, I recommend that you head out and test the theory by moving your ISO setting around in varied lighting conditions.
I hope that this series has been helpful, and has provided you with the confidence to go out and play around with the exposure triangle. It’s practice that makes perfect after all, and I hope that you can make the time to go out and play around with your photography.
Written and photographed by Amanda Ritchie, Londolozi Photography Studio Manager