The Magic of Auto ISO

What's the definition of Auto ISO and why would you want to use it? Let's start with regular ISO setting. It's the setting you choose on how much light your camera sensor needs for a good exposure. Auto ISO let's the camera pick the ISO setting for you.

Auto ISO Header

If you've advanced your photography to more than just a snapshot shooter, you've likely moved past Auto-Everything mode and you've delved into trying aperture priority and shutter priority camera settings.

Intentional motion blur backgroundIntentional motion blur

Shutter priority is the dominant mode to use for sports and action photos where you want to set the shutter speed to freeze the action or get just the right amount of motion blur intentionally.

Aperture priority is loved by portrait photographers and landscape photographers who want to control the depth of field.

Wouldn't it be cool to have total creative control and be able to set both the aperture and shutter and get the right exposure in any lighting situation? Well, now you can with Auto ISO.

Aperture PriorityAperture Priority

Shutter PriorityShutter Priority

Automatic ISO will give you the ability to set your shutter speed exactly where you want it to be, combine that with the f/stop that gives you the right amount depth of field you want, and let your camera do the rest.

This is a great thing for you when you are shooting in rapidly or dramatically changing light conditions. Your camera can automatically adjust much faster than you can and still give you the shutter speed and f/stop you want.

Increasing the ISO is really just increasing the amplification of the signal the sensor got during the exposure of the light that was present. Your camera's lowest ISO setting doesn't use any amplification.

One good example of when you'd want to use this ISO setting is when photographing birds in flight. They're moving real fast and may fly into shade or sun areas or fly to an area with a different background brightness.

Fast shutter speed and medium aperture required higher ISO

You're looking at maybe a minimum of 1/000 second to freeze the action. You also don't want to shoot wide open at the biggest aperture for fear that you'll miss the focus. You could set the f/stop at f/5.6 or f/8 to give yourself a little latitude in depth of field.

Then you can leave the best ISO setting up to your camera to decide in order to get the exposure right.

How to use Auto ISO in Manual Mode

Nikon and Canon menu listings can be seen in this post and it’s beyond the scope of this post to point to every camera model’s exact location. Refer to your owner’s manual for more information on how to set the Auto ISO maximum.

  1. You first set your camera on manual.
  2. Then set the shutter speed and aperture to the settings you want.
  3. Finally, dial in your ISO to "A" for auto.

You can find your ISO settings somewhere in your camera's menu. It's beyond the scope of this post to provide every camera's exact location. Consult your camera owner's manual for information specific to your camera model.

Your camera will select the needed sensitivity of your sensor to the proper ISO level to get a good exposure. Exposure isn't always perfect. But, just like aperture priority and shutter priority, you can tweak exposure levels if needed with software.

The exposure triangleExposure Triangle

You can use the automatic ISO setting with aperture and shutter priority too, but you give up the control of that component of exposure and the camera's choice  likely won't align with your ideas of what you want to do.

You can Adjust The Range You want in Auto ISO

You can go into your camera's menu and limit the range of camera ISO setting you want your camera to use.

If you're concerned about image quality at those super high ISO setting you may want to limit the highest ISO in auto at ISO 1600, rather than the maximum of 25,600.

With sophisticated DSLR cameras, you can limit the ISO range.Auto ISO Range Setting

The History of Auto ISO

It's been around since 2004 on Nikon DSLR cameras and Canon followed with this feature on its 7D about 5 years later. Since then, due to the increase in sophistication of digital camera features, auto ISO capability is included on a lot of cameras.

It's only been recently that it's become more of a topic of discussion on photography blogs and in the world of digital camera talk. There's been an ANTI-AUTO-ISO stigma in the digital photography world for two reasons.

1. Auto-phobia. Pros and advanced amateurs like us don't want to be accused of using automatic settings. We're control freaks and we want to take control of our camera settings. "Automatic is for amateurs." 

Well, really that's what's great about being able to set your f/stop and shutter speed. You've got the creative say in both of these exposure settings.

2. Noise-phobia. One of the big limitation in the past was the noise and reduction in image quality at higher ISO settings. Not so anymore. The camera sensor technology and post  image capture processing has dramatically improved. So much in fact, that you can get great quality at high ISO settings.

The justifiable concern for using an amplified higher ISO is becoming almost a non-issue.

Video on Auto ISO

This video is a little lengthy, but it's really worthwhile to watch if you have a few minutes. It covers a lot of good information on this topic. Steve Perry is Nikon shooter, but we won't hold that against him.  ( :-P)

My Auto ISO Challenge

I've been emotionally stuck on aperture priority mode because of all the portraits I shoot. Portrait photographers like to concentrate control of focus and sharpness on both the subject and the background.

I'm the first one to admit I'm guilty of not venturing out of my comfort zone at times and trying something new. In order to grow as a photographer, I'm leaving my cameras ISO setting on "A."

Does this mean I'll totally convert over to using Auto-ISO entirely? Not likely. Should you switch too? You should give it a try. I think you'll be pleasantly surprised at how much fun it is to set both f/stop and shutter speed.

When You Shouldn't Use Auto ISO

There are only a few specific instances where setting ISO on auto does not serve you well.

  • When you use flash it won't work properly.
  • When you are controlling the light rather than using existing light, such as when you are shooting photos in a photo studio with strobes or floodlights.
  • When it's super bright you're going to be on your camera's lowest ISO setting (often 100).

In most other situations where you, the creative photographer, wants to have control over shutter speed and aperture, it just makes sense to use it. have a blast playing! If you found this article worthwhile, please share it. Shoot More. Watch Less TV.


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