ISO is the number that refers to the sensitivity of the sensor – the higher the number, the more sensitive the sensor, but, along with a higher sensitivity, there is also a reduce in quality, or an increase in grain. Grain is the sandy effect over an image that is synonymous with film photography – it can be used artistically though, it creates a vintage effect and paired with some good editing can add a certain emotion to an image. ISO ranges from a very low 50, to a standard (highest quality) 100, all the way to the most sensitive (on the majority of cameras) being around 6400. With the invention of digital photography, ISO is now something you can change on the camera – it used to be that the roll of film you chose had a set ISO (this is because the film is the equivalent of the modern the sensor.)

As you can see, the first image is 100 ISO, the second image is 800, and the final image is 6400 – and with each bump in ISO the amount of grain increases, indirectly proportional to the quality. The amount of light doesn’t change in these because I adjusted the shutter speed for each ISO change.