[pure-silver] Re: estimating filter factor: gray card?

  • From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
  • To: <pure-silver@xxxxxxxxxxxxx>
  • Date: Tue, 3 Oct 2006 15:24:53 -0700


----- Original Message ----- From: "BOB KISS" <bobkiss@xxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Tuesday, October 03, 2006 8:13 AM
Subject: [pure-silver] Re: estimating filter factor: gray card?


I give up.

We are at cross purposes.
The problem is that the square law refers to the diameter of the aperture rather than stops. A factor of 8 times is requires increasing the aperture 3 stops but that is an increase in diameter of the aperture by the square root of 8 = 2.8.
The ratio of light intensity produced by changing stops is the function 2^x where x is the number of stops.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx

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