You may already know about the ISO setting on your camera.  This setting controls the camera’s sensitivity to light.  The higher the number, the more sensitive it is to light.  For hand-held photography, generally you can shoot at lower ISO settings in bright scenes, and you will have to move to higher ISO values in lower light.

There is a tradeoff when you move to higher ISO values.  The image becomes more “grainy” due to a phenomena called “digital noise” that degrades the photo.   Cameras are getting better all the time with abilities to go to very high ISO values.  Generally you want to avoid the highest ISO settings on any camera, and stay as low as possible.  Built-in high ISO noise reduction and features to reduce noise in programs like Adobe Lightroom can help, but you are still better off not having the ISO go higher than it needs to be.

How high does it “need” to be?  The answer lies with the shutter speed.  If you are shooting hand-held, the shutter speed needs to be fast enough to minimize motion blur caused by hand movement.  A very general rule of thumb is to keep the shutter speed at 1/(focal length), so it depends on the focal length of your lens.  The longer the focal length, the faster the minimum shutter speed should be.   Other factors like sensor crop factor and whether you have Image Stabilization/Vibration Reduction also affect that, but the general rule is a good starting point.

The other reason you might need a higher ISO to achieve a faster shutter speed is if you are trying to freeze motion of the subject in the photo, as in sports or active wildlife.

As you move to higher ISO values, you can shoot at faster shutter speeds.  If you need the shutter speed to be twice as fast, simply double the ISO.

Assuming you  are just trying to minimize the effect of hand motion blur, there are two ways you can deal with the problem.  Move to a sufficiently fast shutter speed using the rule above, increasing the ISO as needed, OR put the camera on a tripod.  If the camera is on a tripod, you don’t need to move to a high ISO to minimize hand vibration. That shutter speed rule ONLY applies when shooting hand-held.

Auto ISO

Many cameras offer a feature that can help you get sharper hand-held shots.  Canon and Nikon deal with it a little differently so I’ll explain both approaches.

Canon  has a special ISO setting called “Auto”.  When you use Auto ISO while shooting in Av (Aperture Priority) Mode, the camera takes control of the ISO to try to ensure the shutter speed is fast enough to minimize blur caused by hand vibration.   So, if you increase the lens focal length, you’ll see the camera automatically increase the ISO.  Or in Tv (Shutter Priority) Mode, the camera ensures the ISO is high enough to enable you to use the shutter speed you have chosen.  Or in Manual Mode, you can set the shutter speed and aperture to whatever you want and the camera will try to pick an ISO that enables you to use those specific settings.  Auto ISO is pretty handy.  On my Canon EOS 6D, it does a pretty good job with Auto ISO. But note that this is primarily used when doing hand-held photography.  When shooting on a tripod, you don’t need to follow that hand-held shutter speed rule and you don’t necessarily need to raise the ISO to higher values because the camera is already stable because of the tripod.  (Note: turn off the Image Stabilizer when shooting from a tripod.)

ISO Sensitivity Auto Control

Nikon doesn’t have “Auto ISO” but has something similar.  Nikons have ISO Sensitivity Auto Control.  You have to configure its settings through the menu.  The basic idea is that the camera lets you pick the ISO and if the camera detects that you have made a poor ISO choice for hand-held photography, it automatically intervenes and changes the ISO to a more appropriate value.  There are various parameters you can control from the menu, so you’ll want to check it out.  Again, this isn’t necessarily appropriate if you are shooting from a tripod.

I encourage you to explore these options and become familiar with how they work.  As with all tools, they have a time and place where they come in handy.

Happy Picture Taking!

Kevin Gourley