If you’re like me, you work a long day out of the home, departing as the sun is coming up and returning after sundown. You would think that this would impose extreme limits on your ability to take meaningful daily photographs. I beg to differ—winter is a wonderful time to push yourself creatively by pushing your camera to extremes by cranking up your ISO!
ISO is one third of the exposure triangle, which is also comprised of aperture and shutter speed. The selected ISO speed determines how sensitive the camera sensor is to incoming light. Doubling the ISO speed doubles the camera’s sensitivity to light. Therefore, increasing the ISO a full stop from 800 to 1600 requires stopping down the aperture by a stop in order to create an equivalent exposure, granted shutter speed remains constant. However, increasing ISO comes with a bit of baggage: added noise. To many digital shooters, this is an undesirable trait as it muddies up the photograph.
To minimize the amount of digital noise in a scene, set the ISO to the lowest value to obtain a correct exposure. My strategy when shooting in low light settings begins with setting the desired aperture and shutter speed based on the available light in the scene, and then setting the necessary ISO after spot-metering my subject using the Zone System. Oftentimes a high ISO value is inevitable to (1) obtain a correct exposure, (2) get the intended subject(s) in focus, and (3) avoid unwanted motion blur in the subject.
Here are a few pointers on shooting in low light scenes with their requisite high ISO settings:
- Shoot at the widest aperture that makes sense for the scene.
- My go-to lenses for low-light work indoors are my 35mm 1.4L and 50mm 1.4. A fast lens affords much more latitude, allowing more light to hit the sensor at the widest apertures. It’s like having a head start in a race.
- Choose the aperture that is appropriate for the scene—do you want a shallow or large depth of field? Let the ISO speed fall into place after choosing your aperture and shutter speed.