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    Re: Napier Diagram + north from Tassie
    From: Bill B
    Date: 2006 Jan 28, 20:37 -0500

    > Bill, it wouldn't be too difficult for a bloke of your many talents to draw
    > up a nice fresh one, would it?
    Not difficult, just time consuming.  According to Chapman's the lines are
    all at 60 degrees angles to the main vertical degree line.  What I am not
    clear on is the spacing for a degree of deviation along those 60-degree
    lines.  That would have to be retro-engineered. My first guess is that with
    a 60/60/60 triangle the spacing will be identical to the vertical axis. The
    curves of course are what one draws in after finding deviation.
    In searching the internet for the Napier Diagram, I ran across a bit of a
    history on him, and some of his other projects.  A very clever (brilliant)
    fellow indeed.  I would hate to try second guessing him.
    If push comes to shove, will indeed do my own.  Need to think about
    copyright laws before posting.
    Enjoyed your recounting of "men without boards in the companionway?"  How
    the heck did they mange to fill the boat water!
    "Always step *up* into a life raft."  LOL
    Off topic, pulled out some more dusty Ansel books this AM.  He bemoans the
    "K factor" (to HELP us) in most light meters that can cause 1/3 stop over
    exposure, as well as the f-stops in many of his view camera lenses being off
    for smaller openings (higher f-numbers).
    Also tracked down his conversion of foot candles to shutter speed.  Foot
    candles (incident light) once reflected yields foot Lamberts (for example
    100 foot candles reflected off a 50% reflective surface yields 50 foot
    Lamberts. Foot Lamberts divided pi become candles/ft^2, then divided by the
    square root of the f-stop gives the reciprocal of the shutter speed.   Pi
    seems to be a kissing cousin of the conversion factor listed in "Pocket
    Reference" of. 0.31831.  Wow, a long way to go.
    Ansel also stated a Polaroid filter reduced light by about 1 1/3 stops.
    Noticed in the Schneider PDF the number "2" popped up for their "superior"
    filters, but I don't recall the context.  It would appear you have some nice
    gear there.
    Have a great trip.

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