Three Pillars of Exposure (Part 1): ISO

Lighting affects photography more than any other element. Natural lighting is variable during different times of the day and when shooting in different locations. In nature photography, there’s very little you can do to control sunlight or shade, but there are three camera settings that are vital to master in becoming a superb photographer. They’re often referred to as the three pillars of exposure:

  1. ISO
  2. Shutter Speed
  3. Aperture

This three-part blog series begins with ISO.

ISO refers to the International Organization for Standardization. In basic terms, an ISO setting means how sensitive the camera sensor is to light. The larger the ISO number, the more sensitive the sensor becomes. Therefore, the larger the number, the less light is needed to be able to record the image. Each time you double the ISO sensitivity (for example from 100 to 200, or from 200 to 400), the camera needs only half as much light for the same exposure.

ISO is an important tool for photographers to master because it allows us to shoot photographs in dark spaces without the use of tripods or flash. It also allows flexibility where we never had it before, such as allowing us to shoot early morning sunrises or animals in late evening light.

The higher the ISO setting, the less light you need to capture an image. This only goes so far, though, before encountering noise in the image, reduced contrast, and reduced sharpness.

Tip: The higher the ISO setting, the less light you need to capture an image.

Noise refers to those tiny little grains that appear all over the photograph. Reduced contrast is the balance between white and black and colors, and sharpness refers to how crisp the edges of your subject appear. A little noise is not always a negative thing, for some grain can be quite pleasing to the eye and may set a nice overall mood to the photograph. It’s a personal taste.

Also, it’s important to consider if you’re going to be printing the photographs at a small size. Very little noise will show up in a 4” x 6” photograph compared to a poster size.

Different cameras produce different results. For some, ISO 800 may be the maximum you’re willing to go, while others produce amazing results even at ISO 3200. In general, the more expensive cameras have better quality and larger sensors that capture more light and produce better quality images in lower lighting conditions. However, digital cameras have come a long way in the last few years and you might be surprised at the performance of your camera.

The best way to discover the quality is to test your camera. Try taking the same shot in low lighting but using different ISO settings. When you transfer the photographs to your computer, you’ll be able to see at a glance what the maximum ISO number is for your comfort level before quality becomes too compromised.

Many newer DSLR cameras have an “Auto ISO” setting, and where you can set the maximum ISO to a certain number. For instance, you might set it at ISO 800 and know that your camera will never go above that number if it’s automatically adjusting to the lighting conditions, and you’ll never get too much noise or grain for your liking.

What’s your preferred maximum ISO number? Leave a comment below.

In Part 2 of the Three Pillars of Exposure series, we’ll discuss shutter speed, and Part 3 will cover aperture.

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