ISO Question

Why do all that math? Just figure out the right exposure for 11 feet one time. For 16', open up one stop. For 8', close down one stop. 2X for 22' & 5.6', etc.
Or didn't I understand the question?

Most 550EX users know the guide number in meters (55). However, mark me as an American, but I don't always think in meters of distance. I can estimate distance to a subject spot by stepping it off. Then I can convert to meters and do the math from there.

In fact, since it was going to be night, I put up aiming sticks for 20, 40, and 60 feet. The 550EX and camera will work out the exposure as long as it is within the maximum range. I had to know that it was within that range.

---Bob Gross---

I don't think we have made this confusing enough. Shall we add a discussion on the law of inverse squares? I can just see the new guys tossing out their flashes now, or swearing to only use them in Program mode. Heck, I don't blame them.

LOL

Here's a very simple explanation of what this is and why it's important.

http://www.jimloy.com/​physics/inverse.htm


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