Auto ISO Behavior

frostyj75 wrote:

Hello all, I have been using auto ISO here and there to see what all the fuss is about. I have been really pleased with it and generally top the ISO out at 6400. I have found that it appears to raise the ISO before it raises the shutter speed. When I have my 23mm on, I have the settings at Base ISO - 200, ISO Limit - 6400, and shutter at 1/60th. In bright daylight, the shutter will stay at 1/60th and the ISO will be up over 1000 at times. Isn't the ISO supposed to stay at the base and only raise when the shutter is at the limit?

Am I not understanding how auto ISO is supposed to work? It is very frustrating, thinking that I'm going to get a certain SS and then notice the ISO has gone up instead of the shutter. I end up going back to manual ISO, I'm just wondering if there is something I am missing in the equation.

Thanks!

Jeff

To be very honest, I do not really understand what you try to explain...!

In the Auto ISO function you set

- the ISO default sensitivity, means the min ISO value you allow

- the ISO max. sensitivity, means the max ISO value you allow

- the min shutter speed

If the exposure changes, considering aperture and and other settings stay fix,

- the camera will select faster shutter speeds with the ISO at its set default sensitivity

when the scene gets brighter or

- the camera will select slower shutter speeds until it reaches the set min shutter speed at the set ISO default sensitivity

- then increase ISO until it reaches the set ISO max sensitivity at the set min shutter speed

- finally even select lower shutter speeds than the set min shutter speed when the ISO value is at the set max value

when the scene gets darker.

Also, why would the camera raise shutter speed instead of ISO? That's not not going to happen! If at all it can lower the shutter speed instead of raising ISO, but all within the boundaries you set in the Auto ISO function, as explained above.

Herbert