Thanks so much for your positive feedback on the first post in my Brave Manual Mode series! I’m happy to see so many of you creating images with your subject in focus, just the way you want it. Let’s build on your momentum by adding another element of the exposure triangle to your photography toolshed – ISO.
I always like to know what abbreviations stand for, so let’s begin there first. ISO stands for International Standards Organization and it’s a standardized industry scale for measuring sensitivity to light. In our case, ISO measures the sensitivity of the image sensor in our camera. ISO is one of three elements (the other two being aperture and shutter speed) within the exposure triangle that determines the exposure of an image.
The second thing you should know is that the ISO number scale ranges from small to quite large (depending on your camera). A smaller number represents less sensitivity, while larger numbers represent increased sensitivity. In instances where there is low light (i.e. a dark room or a very shady garden spot) you may need to increase the camera sensor’s sensitivity to light (higher ISO). When there’s ample light available (i.e. outdoors on a clear day and without shadows present) you may need to reduce the sensitivity of the camera sensor to light (lower ISO) depending on your aperture and shutter speed, otherwise your image will be blown out. Blown out images are very bright with little visible detail (see image 4 below).
Of the three elements within the exposure triangle, ISO is the one I tend to focus on the least – and that’s because of where and when I shoot. I do most of my shooting outside on clear days during early morning or late afternoon. When the light is good, I usually leave my ISO at 100, which is my lowest setting, and focus my attention on aperture and shutter speed to get my desired exposure.
As a gardener and photographer, I am sure you already pay close attention to light in the garden. So, this brings me to the third thing I want you to know about ISO. If you shoot in the best possible light, you shouldn’t have to worry too much about your ISO setting which frees you to focus on the other two elements. However, ISO is an equal player in the exposure triangle, so you can’t just ignore it. In instances where you need to freeze motion by shooting at a higher shutter speed, you may need to adjust your ISO to get a proper exposure. I’ve had to bump up my ISO in these instances, but before I raise it above ~800, I will adjust my aperture or shutter speed to allow more light into my camera. I’ll discuss shutter speed in the next installment of my Brave Manual Mode series, in case you need help.
Look at the images below to see the impact of ISO on exposure when the aperture and shutter speed remain constant. All four images were taken in a shady spot in my garden.
Image 4: 5000ISO – 60sShutter – 7.1Aperture ** This image is overexposed (blown out areas).Take some time today to find the ISO setting on your camera. Determine the lowest and highest ISO values possible, then take a few practice shots at varying ISOs to see the resulting change in exposure. Now that aperture is under your belt, understanding ISO brings you one step closer to shooting on manual mode!