OM-D: The case against Auto ISO

Started Jul 4, 2012 | Discussions thread
Loga
Contributing MemberPosts: 682Gear list
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It is simple
In reply to Thomas Niemann, Jul 5, 2012

If you have moving subjects, then the original algorithms provides the best result since it cares to freeze movements with the fix lower end shutter speed. And if you don't have moving subjects then you probably have the time to set your camera the most optimal

way, for example change to shutter priority and set a low shutter speed and let the camera set the lowest possible aperture and ISO.

Actually, this is equal to what you want.

Thomas Niemann wrote:

The algorithm for adjusting exposure in decreasing light using aperture priority and auto ISO is as follows:

1. shutter slows down to a predetermined limit
2. then ISO goes up to max ISO (menu E: ISO-Auto Set)
3. then shutter speed goes below predetermined limit

For the Olympus 45mm f/1.8 lens the predetermined limit is 1/(2FL) or 1/100.
For the Panasonic 20mm f/1.7 lens the predetermined limit is 1/(3FL) or 1/60.

With IBIS it's easy to take sharp hand-held images at much lower shutter speeds. So we're boosting ISO and degrading image quality when we could achieve several stops of improvement by simply slowing down the shutter speed sooner.

Perhaps they could add a menu option that lets you select the shutter speed lower bound. e.g., 1/(2FL), 1/(FL), 1/(0.5FL), 1/(0.25FL). And, in the Olympian tradition, refrain from explaining this feature in their user manual.

Meanwhile, the workaround is simple. Don't use Auto ISO. When you set a specific ISO value the algorithm is as follows:

1. shutter speed goes down

That's it. So just keep an eye on the shutter speed and open the aperture or increase ISO as needed.

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