Some Thoughts on ISO 50

mike earussi wrote:

xpatUSA wrote:

mike earussi wrote:

Because there is no AFE (analog front end) in the older SDs and DPs, the ISO setting is software driven (i.e. SPP reads the ISO setting and adjusts the exposure on your monitor accordingly).

One difference I found is that, ISO 50 shots do not have their exposure on the monitor adjusted - as I tried to explain in the OP. In other words, the adjustment factor for ISO 100 is 1, for 200 is 2, etc but, for ISO 50, the adjustment factor remains at 1, not 0.5 which one might have expected.

AFE was added in the SD15 and later DPs resulting in the ISO setting telling the camera to actually amplify the [sensor] signal before recording to the SD card. This had the effect of slightly lowering the noise at higher ISOs but at the expense of lowering the overall DR, a trade-off that not everyone was happy about.

And to further add to the confusion, the Merrills don't have AFE and the Quattros do.

IMHO, the SD14 at iso 50 produces the most noise free skies of any Sigma camera. And if you can get the color balance correct, can produce better looking images than the SD15.

http://www.pbase.com/mikeearussi/sd14_iso_50

Nice shots there, of course. I blame the photographer, not the camera settings

The shots aren't meant to be artistic, of course, but they do demonstrate the noise free skies the SD14 is capable of producing at iso 50.

Yes, did notice the skies, Mike. I do like the SD14 in spite of what "they" say. Sold my first one as fast as I could (was going to shoot JPEGs with it at the time). But they do grow on you.