What is the ISO setting and what does it do?
ISO is your camera's sensitivity to light represented in a numerical value. The term ISO comes from the International Organisation for Standardisation.
Taken on a dull day, by raising my ISO I was still able to keep a high shutter speed of 1/2000th second to get this fast moving Scarlet Myzomela nice and sharp.
It harks back to the days of film photography in the 1960's, when systems of measurement were developed to regulate the sensitivity settings on film. Initially DIN and ASA became the mainstream organisations who standardised film sensitivity.
It was common during the 1960s and 1970s to find film canisters listing two kinds of ratings, ASA and DIN, which were numbers as references to the film's sensitivities, based on the amount of light-sensitive coatings or crystals embedded in the film's structure.
In 1974, these two standards moved to one system and the International Organisation for Standardisation released the ISO standards.
Although still used for measuring the speed of colour negative film, ISO has also morphed into the international standard for measuring the 'sensitivity' of digital sensors. Although technically, 'amplification' might be a better term. But we won't go deep into the technical blah....
Regardless, it's a measurement of how your camera deals with light and the main concern to me, with my limited technical mental ability, is what it does, and not so much how it does it.
A higher ISO number indicates a higher light sensitivity and a greater ability to capture light.
Benefits of using higher ISO are: you can still retain the same aperture and shutter speed settings, but shoot in darker conditions.
The reason higher ISO is so handy for birds is because you generally need to keep your shutter speed relatively high to capture movement without too much blur ... and often you are shooting in less than bright conditions.
Faster shutter speeds give less time for light to reach your sensor, so by increasing the sensors sensitivity, we can shoot in lower light conditions without compromising shutter speed.
The downside to higher ISO, is it will also increase the graininess or ‘noise’ in your photo.
Australian Grebe at ISO 5000 with obvious graininess or 'noise'.
This noise issue can be overcome in a few clicks by using a denoise filter. Most post-processing applications include at least a basic one.
The same photo after using Lightroom's AI Noise Reduction Filter - lovely and smooth with improved clarity!
With my OM-1, I find anything taken with an of ISO 800 or higher benefits from a run through the noise reduction.
Here's a list of popular Denoise applications or software with a built-in application:
I use Lightroom denoise on 90% of my photos - the new AI version is excellent - I don't find the need to purchase an additional extension.
I seem to end up shooting birds quite consistently on ISO 2000 - if it's nice and bright I will drop it down, but I do like to keep a higher shutter speed to increase my chances of a nice sharp image.
Here's my cheat sheet/general guide for ISO in printable format:
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