INTRODUCTION
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/
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.
