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06-04-2011, 07:03 AM   #1
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Why does P shift only work with auto ISO in one direction?

On my K-x, I sometimes use program line shift in P mode. I can use the wheel to shift towards smaller apertures in one direction and towards faster shutter speeds in the opposite direction.

When I shift towards smaller apertures (higher f number), the camera will increase the ISO if necessary to give me the really small apertures.

But when I shift towards the faster shutter speeds, the camera won't increase the ISO when it bottoms out on wide open aperture.

Odd. Can anyone explain why?

Sincerely,
--Anders.

06-04-2011, 07:23 AM   #2
Ash
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Hi Anders.
Is your camera set on auto ISO mode when you're shifting the shutter speed?
If not, then set it to auto and it should compensate.
Otherwise, take a shot to show an example of this at a fast shutter speed and see if exposure is right.
06-04-2011, 01:25 PM   #3
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Original Poster
Thanks for commenting Ash.
Yes the camera is on auto iso. And auto iso takes effect when i flick the wheel to the right to gain smaller apertures. The iso starts to climb when i hit the 2/focallength shutterspeed limit that P mode uses.

But it doesn't increase when i flick the wheel to the left to gain faster shutterspeeds.

I don't think this behaviour is a bug, but rather a deliberate design choice by the engineers. I just don't understand why.

The exposure is always ok. Program line shift in P mode moves between equivalent exposures. You don't have to take an actual picture to experience the phenomenon, you can see it in the viewfinder data readout.

Sincerely,
--Anders.
06-04-2011, 04:15 PM   #4
Ash
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If exposure is always OK, then there isn't anything wrong with the apparent fixation of the ISO. But it doesn't make sense under the same lighting conditions that exposure is equal between a slow and a fast shutter speed given the same aperture and ISO.

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