The three main settings you should consider when exposing a photograph are the aperture, shutter speed, and ISO. These are commonly referred to as the “exposure triangle,” as one must achieve a balance between all three factors to achieve a well-exposed image. Today we will be talking about what ISO is, what it stands for, its effects, and how you can use it to your advantage to take the best pictures possible.
What does ISO actually mean?
The word ISO comes from the abbreviation used by the International Organization for Standardization. The founders chose the term to abbreviate its name (rather than an acronym like IOS) inspired by the Greek word “isos,” meaning “equal.”
The organization sets and maintains various industrial and commercial standards, and the photography market is one of them. Previous camera standards ASA and DIN were combined to create the ISO standard in 1974. At its origins, ISO was a rating for the light sensitivity of photographic film (ISO 100, 200, 400, etc.). The higher the rating, the more sensitive the film was.
The term was adopted to measure the sensor’s light sensitivity with the rise of digital photography.
What is it?
In photography, ISO relates to a sensor’s (or film’s) sensitivity to light. A lower ISO setting makes the sensor less sensitive to light, meaning it either needs more illumination or a longer shutter speed to expose an image properly. Increasing the setting makes your sensor more sensitive to light, allowing you to shoot in darker environments, with tighter apertures, and/or using faster shutter speeds.
How is it measured?
ISO is measured in numbers. While manufacturers used to stick to ISO 100, 200, 400, 800, 1600, and so on (doubling in value), things have changed with more recent cameras. Smaller increments have been introduced for better refinement, but the concept is the same. ISO 100 is half as sensitive as 200, which is also half as sensitive as 400.
The effects of manipulating ISO
The effects of changing the value are simple to understand. A higher setting will make a sensor more sensitive and, therefore, make an image brighter. At the same time, increasing the ISO creates more grain or noise. It is not mentioned often, but a higher ISO can also deteriorate dynamic range and colors. These are important reasons to stay as low as possible.
Look at the images above to see an example of differences between low and high sensitivity levels. I didn’t alter these images with editing. All I did was crop them so you can better inspect the differences. Furthermore, it must be noted they were shot with a Nikon D610, which has a full-frame sensor. Such bigger sensors are significantly superior when handling noise. The differences will be more obvious when using smaller sensors.
With that in mind, the images above show a significant difference in image quality. Not only is the high-ISO one grainier, but the quality in colors and dynamic range have changed.
When should I increase the ISO?
I have said it time and again: grain can’t ruin a good photograph. Composition, subject, meaning, and many other intangibles are far more important. Play with the sensitivity; just be conscious of why you’re doing it and its consequences.
Grain can't ruin a good photograph.
A lower ISO will create a better-looking image, so our general advice is that you only increase it when totally necessary. If there is not enough light, you need a tight aperture, or want to keep a faster shutter speed, then your only option is to increase sensitivity.
Photography is a complex art, so we have put together a series of tutorials and in-depth material for you to learn more!
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