Rowse provides 2 example photos of the same object at 100 and 3200 ISO settings. I have modified these pictures to create a side-by-side comparison with the ISO speeds in white text.
Notice how the 3200 ISO has an increased “grainy” quality and that it appears to be brighter than the 100 ISO equivalent. The increased sensitivity to light on automatic settings will allow for recalculations on aperture and shutter speed. According to Rowse, “When you do override your camera and choose a specific ISO you’ll notice that it impacts the aperture and shutter speed needed for a well exposed shot. For example – if you bumped your ISO up from 100 to 400 you’ll notice that you can shoot at higher shutter speeds and/or smaller apertures” (Rowse).
As a general rule of thumb, ISO is one of the last things you will want to adjust when taking pictures. Think of a film camera, the photographer wouldn’t change out rolls of film with every shot! When we use our digital camera, we need to keep in mind: “When you increase the ISO setting, you’re not really making it more sensitive to light, you’re simply amplifying the light values it’s managed to capture…Usually, you don’t see it because it’s faint compared to the light falling on the sensor, but when you increase the ISO, you amplify it, and it shows up as a kind of random speckling. The higher the ISO, the worse the noise” (Meyer). A good rule of thumb is to try different aperture settings and shutter speed settings before adjusting your ISO sensitivity.
Meyer, J. (2014, February 18). What is ISO: Camera sensitivity settings (and the best ways to use them) | Digital Camera World. Retrieved March 11, 2015, from http://www.digitalcameraworld.com/2014/02/19/what-is-iso-camera-sensitivity-settings-and-the-best-ways-to-use-them/
Nikon. Understanding ISO Sensitivity. (n.d.). Retrieved March 11, 2015, from http://www.nikonusa.com/en/Learn-And-Explore/Article/g9mqnyb1/understanding-iso-sensitivity.html
Rowse, D. (n.d.). ISO Settings in Digital Photography. Retrieved March 11, 2015, from http://digital-photography-school.com/iso-settings/
Rowse, D. ISO Settings in Digital Photography. Retrieved March 11, 2015, from http://digital-photography-school.com/iso-settings