Tuesday, October 14, 2014


In this digital age ISO is now a tool to get me to the f-stop/shutter speed combination I need for a given subject.  It's completely variable and at least with a professional full-frame, or larger, camera we can use ANY ISO we want and still get great images. 

In the old days our ISO choices (ASA back then) were only incrementally variable. Our films had a "fixed" ISO for best results.  Sure there were some notable exceptions like Tri-X and later T-Max Black and White films that we could "push" one or two stops higher and get great, grainy, results.  I used to push my 320 ASA Ektachrome slide film to 1000 ASA with nice results when photographing rock concerts.  Having the freedom to move my ISO so I can use the shutter speed and f-stop I want is the best thing about digital cameras! This is especially true for action/sports photography.
f5.0 @ 1/2500 sec., 800 ISO, lens @ 200mm

Since this rider was racing towards me at a full gallop I needed a high shutter speed--especially with a relatively wide f-stop--so, 800 ISO was the necessary ISO to use.

f50 @ 1/30 sec., 1600 ISO

This antique pump at the State Fair was in a shaded area and to make the spinning rotor transparent I needed a slow shutter speed. At f5.0 for adequate depth of field I needed 1600 ISO.

f5.0 @ 1/2000 sec., 125 ISO

This ice encrusted leaf was in a lot of back light and with a slight breeze I needed a high shutter speed to freeze it.  I also wanted a shallow depth of field. So, with that shutter speed I had to drop the ISO down a lot.

As you can see in each case I don't pre choose my ISO --as some photographers teach on the internet to always use your camera's native (lowest) ISO--NO, all you do then is limit your creative possibilities.

Our most creative tools in photography, besides lens choice, are f-stop and shutter speeds. You can't use their full range of possibilities without a really variable range of ISO's.

As usual, should you have questions please don't hesitate to ask...

Author: Jerry W. Venz, PPA Master Photog. Certified
Training site: http://www.LightAtTheEdge.com

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