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What is Auto-ISO and how to use it?

Shutter speed, aperture and ISO are the three main variables for getting a properly exposed photograph. Digital camera manufacturers provide the freedom to adjust the value of ISO, shutter speed and aperture easily on the fly. In situations where aperture and shutter speed aren't enough to give a good exposure photograph, ISO helps a lot. Though with tremendous advancements in digital sensor technology and noise reduction algorithms, shutter speed and aperture have become more crucial factors than the value of ISO in digital photography. If you are a total beginner and want to learn the basics about ISO first, here is my post about how ISO works

Is Auto-ISO good or bad?


What is Auto-ISO?
Both aperture and shutter speed can affect a digital photograph in a way that it can be impossible to salvage a photograph. Example: Depth of field cannot be fixed later, neither motion blur. Keeping these two problems in mind for a fast-paced environment, it is preferable to fiddle around with ISO. Extending the ISO control further, a new feature called Auto-ISO came into existence from various camera manufacturers. Auto-ISO refers to automating the increase and decrease in the value of ISO depending on the amount of light available. Auto-ISO offers more convenience to the photographer, as you can set a maximum allowed range of ISO and forget about changing ISO after that. If it gets dark, ISO will increase automatically. If there is plenty of light available, the ISO value will be decreased.



Manual + Auto-ISO
Ability to use Auto-ISO feature in manual mode offers great flexibility and can be a blessing for situations where light changes every few seconds. You can set the maximum range of Auto-ISO to a value like 6400 or even higher. When the available light changes, the camera will auto adjust the value of ISO to compensate. In low light conditions, the maximum value of ISO selected by the camera would be the one defined by the user in settings.

Aperture priority + Auto-ISO
In aperture priority mode with Auto-ISO, minimum shutter speed value is set to trigger an increase in ISO. This value is usually 1/(Focal length). First, the camera will keep increasing the shutter open time if the available light keeps decreasing.  Once the minimum allowed shutter time limit is reached, the value of ISO will go up to compensate. This helps to reduce blur introduced due to possible camera shake or not so steady hands. 

Is Auto-ISO good or bad and when to use it?
Auto-ISO feature can be extremely beneficial for sports, wedding, and other fast-paced environments. One less variable to worry about greatly improves the overall efficiency to get good shots. But where does Auto-ISO fail or is not recommended? For landscape and long exposure tripod work, auto ISO is not necessarily required as there is a fair amount of time to adjust the settings. In a situation where the user has full control of conditions such as a portrait studio, use of Auto-ISO is not recommended. This is because Auto-ISO can cause inconsistent jumping around of ISO value in between multiple shots. Another situation where Auto-ISO is not recommended is when using an external flash. In the next section, a list of cameras with Auto-ISO is mentioned to help you decide on a camera body. 

List of Canon cameras with Auto-ISO:
Canon 6D
Canon 6D Mark II
Canon 5D Mark II
Canon 5D Mark III
Canon 5D Mark IV
Canon EOS-1D X
Canon EOS-1DX Mark II
Canon EOS 5DS / EOS 5DS R
Canon EOS 7D Mark II
Canon EOS 80D
Canon T5i
Canon 60D
Canon 77D

List of Nikon cameras with Auto-ISO:
Nikon D610
Nikon D800/D800E
Nikon D5500
Nikon D7200
Nikon D7100
NIkon D7000
Nikon D5600
Nikon D750
Nikon D610
Nikon D850
Nikon D80
Nikon D3400

List of Sony cameras with Auto-ISO:
Sony A7 II
Sony A7 III
Sony A7R II
Sony A7R III
Sony A6500
Sony A6300
Sony A6000

Hope this post helped you to understand the Auto-ISO feature, give it a try and see if you like it.  Questions are welcomed in comments, happy photography. :) 

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