One thing that makes a digital camera exciting is the fact that one can change the “sensitivity” of the image capturing sensor at any time, from one frame to the next.
A film user must carry rolls of film with different ISO numbers and waste film when it’s necessary to change the ISO before the end of a roll. A digital camera can instead use AUTO ISO for automatic sensitivity adjustments, or one can adjust the camera manually for a different ISO on each shot. When one combines flexible ISO with the ability to change color saturation levels on the fly, a digital camera allows great adaptability to various light and color conditions.
Why write an article on the humble act of changing ISO settings? Well, the Nikon D2x has more than the usual amount of flexibility in its ISO system. When one adds in things like Noise Reduction, and modifiable ISO stepping (1 step vs. ½ steps) the D2x has some things to consider, and some decisions to make.
WHAT IS THE ISO?
The International Organization for Standardization (ISO) is a worldwide federation of national standards bodies from over 150 countries; one from each country. They do not develop all standards but, as with ANSI, provide a means of verifying that a proposed standard has met certain requirements for due process, consensus, and other criteria by those developing the standard. So, in short, they are the central body for formation and dissemination of industry standards for all other national standards bodies. Here is a link to their website: http://www.iso.org/
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As applied to photography, an ISO number, such as 100 or 400, in one’s camera, is an agreed upon value on sensitivity for an image capturing sensor or film. Virtually everywhere one goes in the world, all camera ISO numbers will mean the same thing. With that fact being established, camera bodies and lenses can be designed to take advantage of the ISO sensitivity ranges they will have to deal with. Standards are good!
In the D2x the ISO numbers are sensitivity equivalents. To make it very simple, ISO “sensitivity” is the digital equivalent of film speed. The higher the ISO sensitivity, the less light needed for the exposure. A high ISO setting allows higher shutter speeds and smaller apertures.