What Is ISO in Photography? What is ISO on a camera?
The name stands for International Organization for Standardization. The International Standards Organisation is a body composed of representatives from various national standards organizations. They formed in 1947 and has it’s headquarters in Geneva, Switerzland.
Where Did ISO Come From?
Ever since the photographic emulsion was developed, different countries tried to enforce standards. This is so they knew what photographers could do with the film. These classifications are now known as film speed.
There were many different groups of people who tried to come up with a method that classified their film in the best way. This is the early process of trying to work out what we now call film speed.
What Does It Mean?
So, as we saw, ISO is a way to classify your film speed and how sensitive to light the film is. Low ISO numbers mean low light sensitivity. They need a lot of light to expose correctly. High ISO numbers have high light sensitivity, meaning they need less light for exposures.
They are in the range of 50, 100, 200, 400, 800, 1600 and 3200. There are other films that are outside this range, but they are more specialized.
These increments seem a little strange. But what you will notice is that the numbers are either doubled or halved. This is because moving your ISO setting from ISO 100 to ISO 200 halves the light sensitivity of the film. Moving from ISO 200 to ISO 100 doubles it.
Is ISO Part of Exposure?
The ISO of your photography depends on many factors. It comes down to how much light is available, and what you want to capture. We tend to try and shoot with a low ISO on our camera as that gives us the best quality and a smaller amount of noise/grain.
The ISO is a little complicated than the sensitivity the film or sensor is to light. Its just a number that correlates with how much light you find in your scene.
How Does ISO Affect Exposure?
The camera’s ISO scale is similar to shutter speed in the sense that, when doubled, the exposure is also doubled. They are proportional to one another. A low ISO number will give a low exposure and a high ISO will give a high exposure. It’s much simpler then aperture.
This is much easier to demonstrate using actual photos as you can see in the slideshow below…
The photos are displayed in the following order: 100, 200, 400, 800, 1600, 3200. The aperture and shutter speed remain constant throughout these photos. Only the ISO is changing so that you can see its effect on a photo.
How Does ISO Affect the Quality of Photos? or How Does ISO Affect a Photo?
As a general rule, the lower the number, the better the quality of the photo. By doubling the ISO in-camera settings, you’re doubling the exposure taken, and in turn, doubling the digital noise.
This noise reduces the detail of a photo by making the image appear grainy and uneven.
Sometimes you cant get away from it. Photographing a bad in a poor lit basement means you need to use an ISO of 3200 or more. You can use ISO 100, but then you need to collect the light through another setting.
To best show how camera ISO affects the image quality, I took another series of photos and displayed them below.
For this experiment, I changed the shutter speed and aperture of each photo rather than changing the ISO.
What is the Best ISO Setting for Low-Light?
The best setting for low light depends on you camera. The more modern the camera and more high end, chances are it does better in low light situations.
Modern DSLRs can extend their ISO way beyond their native range. The Canon 5D Mark IV has an expandable ISO that reaches 102.400. You wont want to print from it, but it helps you in a pinch.
Other cameras work much better in low light conditions, as that is a main feature. So a decade old DSLR might need an ISO reach of 6400, where as newer ones might get away with 3200 or lower for the same situation.