Digital ISO
A while ago I was confronted with a problem. Due to poor weather conditions, an event I was to photograph was moved indoors – not outdoors as expected. This meant poor lighting conditions. I couldn’t use flash and so I did the next best thing – I turned up the camera’s ISO.
ISO which stands for “International Organization for Standardization” is better known among photographers as the setting for film speed. The ISO predecessor was ASA (American Standards Association) and prior to that, film speed was rated as DIN (Deutsches Institut für Normung which means – German Institute for Standardization).
Modern film cameras allow us change the camera’s ISO setting to that of the film being used so that we can use a higher ISO film for low light conditions and a lower ISO film for brightly lit conditions. Even on digital cameras, there is an ISO Setting. This emulates the film camera’s ISO control in as much as it turns up the sensitivity of the sensor (as opposed to adjusting to the sensitivity of the film) so as to handle low light situations.
As it turned out, I was able to take some shots outside at 200 ISO, but for the indoor shots, I simply turned the ISO up to 1600. Had I been using a film camera I would never have been able to photograph the indoor portion of the event because I would not have taken 1600 ISO film with me – and because of the location, and the event being on a Sunday, I would not have been able to buy 1600 ISO film locally. So – it’s nice to have that versatility built right into the digital camera.
For most uses, the ISO can be set to between 100 and 400 ISO. Above 400 ISO, the images start to show what is known as “noise” – electronic interference which gets exaggerated as the signal is boosted. This is commonly known as have a low ’signal to noise’ ratio. High speed film is not without it’s problems as higher speed film appears grainer than with lower speed film. There is no cure for the grain effect in film, however there is a cure for the noise in digital images. There are several very good programs available that will reduce this noise. The one I use is by Neat Image- and it’s free! Here is an example -
The first image was taken at 100 ISO
The second image was taken at 1600 ISO (Same aperture – different speed to compensate for the change in ISO). Notice the noise – the green and purple speckles
The third image was taken at 1600 ISO. It was then filtered using Neat Image. As you can see, it’s nearly as good as the 100 ISO image.