ASA / ISO Settings

Urban Tastes

ASA determines the sensitivity to light of your camera’s sensor.  The higher the number the more sensitive to light the image will be.  A good example, a higher ASA/ISO rating would be a better choice during darker situations rather than a lower setting while a lower setting is better in a brighter situation.

The best ASA rating during daytime is a low setting of 100 or 200 where as in a darker situation (dusk or early evening) you would want to adjust the reading to a higher setting like 400 or 800.  This is a basic concept giving way to a more important factor.  Shutter speed.

The more important goal of an ASA rating, (regardless of the situation) is to keep the shutter speed high enough that “shutter blur” doesn’t occur.   No matter how great an image is, if it’s not sharp, it’s worthless…that is, unless it’s a blurred image that you’re going for.

A good “rule of thumb” is to keep your shutter speed as close to the millimeter of your lens as possible.  In other words, if you’re shooting with a 105mm lens you need place your shutter speed around 125/sec to eliminate “shutter blur” from occurring. 

More times than not, this adjustment can be done with the balancing of shutter speed and aperture but there are those situations where you will need to raise the ASA rating to meet the shutter speed for sharpness.  At this point ASA becomes your 3rd choice for correct exposure after shutter and aperture settings.

There are certain aspects that naturally occur when using a higher ASA rating concerning contrast, color saturation and noise but in critical moments you might have to ignore basic drawbacks, bite the bullet and get the shot!

A usable image is paramount above all things.  If it’s not usable, you don’t get paid plus you may face embarrassment not to ever shoot for that client again.  At very least…you lost your shot never to get it again.

Many times during my location photo sessions I’m adjusting my ASA rating.  Think of it as a 3rd tool along with shutter speed and aperture adjustments rather than a setting that is unchangeable.