auto ISO+auto Shutter speed and lens focal length
wait, really? in Tv or in iA?
I see it happening in P and A modes on my GF1. In iA mode (full auto) it doesn't seem to do it. That is, in iA mode I see the shutter speed displayed drop below where I'd expect the camera to have increased the ISO. It does change with zoom but it isn't as obvious and repeatable as in P and A modes. In S mode (this isn't a Canon :smile
the shutter is fixed by me and the camera doesn't override it.
Specifically, GF1 + 20mm f/1.7, AUTO ISO setting, starts raising the ISO higher than the base 100 ISO once the shutter speed drops to 1/30th of a second. The shutter speed doesn't drop lower than 1/30th until the ISO reaches your configured ISO limit (I used 1600 for testing, but it works the same with other ISO limits)
And GF1 + 14-140mm f/4-5.6, AUTO ISO setting, starts raising the ISO higher than the base 100 ISO at a speed which depends on the zoom of the lens. To me it looks like it's doing roughly this:
14mm-30mm: tries to keep shutter above 1/30th of a sec
30mm-40mm: 1/50th
40mm-50mm: 1/60th
50mm-60mm: 1/80th
60mm-80mm: 1/100th
80mm-100mm: 1/125th
100mm-130mm: 1/160th
130mm-140mm: 1/200th
Btw OSI stabilization on or off makes no difference. And the speed increases are not coupled with the decreases in lens aperture.
To see this with the zoom lens is easy b/c the aperture/speed/iso values change on the LCD as I hold the shutter down half way and zoom the lens. All I need to do is pick a subject bright enough not to cause the ISO to reach its configured maximum, but dim enough not to cause the camera to up the shutter speed to compensate. A tree's leaves in half sunlight did the trick right now.