Expose Right

On my recent workshop in Iceland (July, 2003) I had a fascinating chat with Thomas Knoll about signal to noise ratios in digital photography. You may recognize Thomas's name — he is the original author of Adobe Photoshop, and also the author of Camera RAW. (A discussion with Thomas is featured in The Luminous Landscape Video Journal, Issue #6, from the Fall of 2002 when I was reviewing a pre-production Canon EOS-1Ds). But I digress.
We spent a lot of time chatting about digital topics during our 3,000 km drive around Iceland, and Thomas elaborated on one that had not occurred to me before, though once I started thinking about it makes perfect sense.

Clouds and V Formation. Iceland — July, 2003
Canon 1Ds with 70-200mm f/2/8L IS lens at ISO 400

Home on The Dynamic Range
Let's assume for the purposes of illustration that a digital SLR has a dynamic range of 5 stops (it's usually closer to 6 stops, but let's not quibble). When working in RAW mode, which you should be, most cameras record...