There are a lot of photographers out there who will do a facepalm whenever they hear someone say auto anything, when talking about digital photography. I too have done the same when I hear some of the weird and wonderful things about photography that the interwebs have to offer. But bear with me, this auto is a conscious decision and not one that just lets the camera take over completely.
Auto ISO with a twist, or as I have also heard it called Floating ISO, lets you set parameters for the camera so that when you need it, the ISO can change, as the “auto” part suggests. You can also set a limit to how high the ISO goes. The cool part of this as far as I’m concerned, when paired with Aperture Priority, is that you also set a minimum shutter speed that the camera will not go below unless the light really falls off. In that case the camera sets the Iso to the highest limit you have set and then lowers the shutter speed to get an appropriate exposure. This is how I have my camera set up:
Aperture Priority with an aperture of my choosing
Auto ISO set to use a maximum ISO of 5000
Minimum Shutter Speed = 1/100 sec.
The photo above, made in the Cloisters at Gloucester Cathedral, handheld on a dreary, rainy day in December (yes, all you Harry Potter fans, you do recognize this hall). Here is the EXIF info from this photo using Aperture Priority and Auto ISO with a twist:
Shutter Speed 1/100 sec.
Exposure Compensation -1.3 EV
What is that you say? Exposure Compensation of -1.3 EV? So how does that work? Well, that is one of the beauties of this way of using Auto ISO. Exposure Compensation in this case forced the shutter speed as well as the ISO to change using Aperture Priority. By raising the shutter speed to 1/100 sec., the minimum shutter speed I set, then lowering the ISO the resulting exposure was 1.3 EV less than what the camera’s meter would have chosen. In this case the ISO was the only thing the camera could change because I set my aperture and the camera used the lowest possible shutter speed that I set when setting this up. If your camera will let you do this, why not give it a shot? I use this form of Auto ISO so often that I have set up one of my user settings work this way. All I have to do when I want to use Auto ISO with a twist is go to U1 and I’m all set.