This video lesson is extracted from the Blurry to Tack-Sharp Photos: 4-Step System. More details on the system can be found - here.

In this lesson, you are going to learn more about ISO than 90% of professional photographers. The myths and misconceptions about ISO are actually published on respected industry websites. You, a photo enthusiast will be able to educate your professional photographer friends!

What is ISO and shutter speed?
Both these manual controls can be increased/decreased to brighten or darken a photo. Each has pros and cons for increasing and decreasing. The goal when changing these settings is to balance these trade-offs to capture a sharp, detailed and vibrant image.

ISO is NOT an acronym!
Most professional photographers believe that ISO is an acronym for the 'International Standards Organisation.'

Here is the quote from the International Organisation for Standardisation website:

'Because 'International Organization for Standardization' would have different acronyms in different languages (IOS in English, OIN in French for Organisation internationale de normalisation), our founders decided to give it the short form ISO. ISO is derived from the Greek isos, meaning equal. Whatever the country, whatever the language, we are always ISO.'

ISO was the 'standard' measurement of photographic film sensitivity to light (film speed). The speed of the film was referenced by its ISO number. The higher the number, the more sensitive it was to light to capture more usable images in low-light.

In a nutshell, ISO means equal (standard) not an acronym for the organisation - it would have been IOS!

ISO is NOT sensor sensitivity!

ISO speed transferred to digital photography and referred to as 'sensor sensitivity. The function of ISO in digital photography is actually applied gain. The function of ISO in digital photography is actually applied gain.

Gain signifies the increase/decrease in the image's brightness after capture.

Ready to get more technical?
The camera sensors consist of tiny units known as pixels. A 12MP sensor means it contains 12 million tiny units or pixels.

As we take a photo, light enters the lens and every pixel measures the intensity of light by counting the number of photons reaching the pixel. The charge of the photons changes the voltage in each pixel; the voltage values are recorded by the camera. The RAW data is a collection of recorded voltage values from all 12 million pixels. The amplification of the signal happens after the data is collected by applying the 'gain'. Digital cameras, including smartphones, should be using the term Gain not ISO!

All data recorded in your smartphone is actually at the lowest ISO setting (the latest iPhone is 32). For simplicity, let's say it is 100 and you captured an image at an ISO setting of 200. When the image is recorded, the gain is applied to boost the brightness by a factor of two.

As you increase ISO, it is at the gradual cost of details, sharpness, and dynamic range. The higher the amplification, the more noise and grain (that speckled look) appear.

In a nutshell, ISO adds brightness!

Why not always leave it at the lowest setting?
At the lowest setting, you do capture a higher range of light and dark details in the image, more vibrant colours. However, the other factor that affects brightness is shutter speed. In most conditions, to achieve the lowest ISO number, the shutter speed has to slow down to let in enough light to make the photo bright enough at the lowest setting..

What is a shutter?

In a traditional camera, the shutter is a mechanical system of blocking and allowing light to enter the camera to hit the sensor. Our smartphones make a click sound to imitate that. Most smartphones have an electronic rolling shutter technique to expose the sensor to light. This means instead of the sensor capturing the scene entirely at once, it captures it row by row from the top to bottom.

Have you taken a photo of a helicopter or other fast movement and noticed a wobbly jelly effect? This becomes more obvious in smartphone video.

What is shutter speed?
Shutter speed is responsible for two things: changing the brightness of your photo, and either freezing action or blurring motion.

The longer the shutter remains open and allows light to reach the sensor the more opportunity for both motion blur and camera shake. This time is measured in seconds and fractions of a second. A shutter number of 1/60 is light hitting the sensor for 1 sixtieth of a second. As the denominator increase, so does the speed - 1/10000 is super fast.

Relax - I will not start doing quadratic formulas with you!

Some Android smartphone cameras can have shutter speeds as slow as 30, meaning the image is captured for a full 30 seconds. This can really only be achieved in low light or placing a filter over the front of your lens that blocks out some light.

What is the best ISO setting for low-light?
When shooting indoors or in low-light conditions, your shutter speed will typically decrease, resulting in camera shake or motion blur. To avoid this blur, you can increase the ISO number.

What is the best ISO setting for landscapes or flowers?
When photographing landscapes, I would recommend where practical to use a tripod and set the ISO to the lowest number available.

What is the best ISO setting for fast-moving subjects?
This scenario is when you start looking at the shutter speed as a priority. My preference is to actually leave ISO on Auto to allow it to quickly and automatically adjust depending on changing light conditions I am pointing the camera.

Practical tips
If you are shooting in manual mode for the purpose of capturing a sharp, detailed image, you should only raise your ISO when your shutter setting creates motion blur.

To maximise your image quality, there are four steps that I follow:

Set the ISO to the lowest value and adjust the shutter speed to a value that achieves the desired exposure.

If your subject is blurry, adjust the shutter to a speed that freezes any movement. Then adjust the ISO to achieve the desired level of brightness.