When I first photographed bears at Katmai, I was using a Nikon 8008 and shooting Fujichrome Velvia 50 and Provia 100. I’d bite my nails, hoping the weather would be nice. If we had clouds and low light, my ratio of usable shots would be embarrassingly low. Photographing a 1,000-pound brown bear running in murky low light at ISO 100 was an Olympian feat. Even with wide-open apertures, my shutter speeds were really slow. I could push (increase the ISO) my 100-speed film to 200, but this only added one stop of light. So instead of shooting at 1?30 sec., I could shoot at 1?60 sec., resulting in grainy, blurry shots. I like to think of this part of my wildlife photography career as my “abstract period.” I produced a lot of abstract motion-blur images, but few tack-sharp shots.
How times have changed. Today’s cameras are technological wonders, and all photographers benefit using these advanced features. The default ISO for many cameras today is ISO 200, and pushing this number higher is the norm, not the exception. I use a Nikon D3 and regularly shoot at ISO 800, 1600 and even 3200, five stops faster than ISO 100. So instead of photographing those bears at 1?30 sec. in low light, I can shoot at 1?1000 sec. Bring on the charging grizzly!
There are lots of ways to take advantage of the high-ISO performance of today’s cameras. But before we explore high-ISO techniques, let’s look at how camera sensors work and what affects their ISO performance.
Camera sensors consist of an array of photosites where light is captured. Sensors capture light (photons) and convert this into an electrical charge that’s eventually converted to a digital value by the analog-to-digital converter. The camera processes this digital value into the final image. Most camera sensors today are either CCD or CMOS.