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ISO Settings: The biggest advance in Digital Photography

Canon ISO Camera Comparison

The ability to change your ISO settings is one of the greatest advantages in digital photography over film.

Those of us who used to shoot film will remember those little film boxes (usually yellow or green) with ASA numbers on them – 50, 100, 200, and upwards.  These numbers denoted the “speed” of the film, i.e. its sensitivity to light.

The digital equivalents of film ASA numbers are the ISO settings

Canon ISO Camera Comparison

Your digital camera will have a menu where you can set your ISO to one of a range of numbers, usually starting at 100 and going to 6400 or higher.  These numbers denote the sensitivity of the camera’s digital sensor to light, with lower numbers being less sensitive than higher ones.

Canon ISO Camera Comparison

What does it mean if the sensor is more or less sensitive to light?  Basically, it means that you will need to let more light into the camera to achieve a correct exposure with a low ISO than with a high one.  To do this, you will either need to use a longer shutter speed, or a wider aperture.  (See my blog about the exposure triangle on 21st September).

I remember when I had my first film SLR camera and was trying to understand the film ASA rating system.  Once I had grasped the fact that a faster film was more sensitive to light, I wondered why you wouldn't always choose to have a fast film in your camera, so that you would never have to worry about camera shake, or low light situations?

Canon ISO Camera Comparison

The answer, of course, is the quality of the image – and this applies to digital just as it used to apply to film.  The higher ISO numbers, while giving you the flexibility of being able to hand-hold in low light conditions, also have a downside – noise.

Noise in a digital photograph is visible as randomly scattered, brightly coloured pixels throughout the image.  These can be particularly noticeable in darker areas, and detract from the overall quality of the photograph.

So the rule of thumb is always to use the lowest ISO setting you can, given the current lighting conditions.

Canon ISO Camera Comparison

Technology is improving all the time, and digital cameras today will perform well at much higher ISO numbers than they did even a few years ago.

One of the huge advantages of digital photography over film is the ability to change the ISO settings between one photo and the next.

You can be taking photos outside in bright sun with your ISO set to 100; a minute later you can go inside a building and take an interior shot with your ISO at 6400.

Canon ISO Camera Comparison

In film days you had to make a decision what film to put into your camera based on the light conditions you were likely to encounter for your next 36 shots!

Who knows! with digital photography in the future, flash photography may become a thing of the past, as higher ISO settings will have become so good that all we need to do is up the ISO settings and still get a great looking image.

Geoff Harris

I am a photography journalist and photographer and currently work as the Deputy Editor of Amateur Photographer (AP) the oldest weekly photographic magazine in the world. Before that I served as the editor of Digital Camera, Britain's best-selling photography magazine, for five years. During my time as editor it became the UK's top selling photo monthly and won Print Publication of the Year at the 2013 British Media Awards. As well as being lucky enough to get paid to write about photography, I've been fortunate to interview some of the greatest photographers in the world, including Elliott Erwitt, Don McCullin, Martin Parr, Terry O'Neill, Steve McCurry and the late Mary Ellen Mark. This has been a wonderful learning experience and very influential on my photography. Beyond writing, I am a professional portrait, travel and documentary photographer, and reached the finals of the 2016 Pink Lady Food Photographer of the Year competition. I am a Licentiate of the Royal Photographic Society and hope to take my Associateship whenever I can find the time.

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