P3D Re: Tom's Base Calculator

[Tom Deering <tmd@xxxxxxxxxxx>]

>Bercovitz/Spicer's Special Cases 2 and 3 both assume a far-point at
>infinity.  Case 2 again maximizes the depth of field, while Case 3
>focuses on the subject near-point, a likely choice for close & macro
>work I would think.  But why no Special Case for focusing on the
>near-point, with a far point *not* at infinity?  That's the situation
>I most likely would be in on my tabletop, or in a think-fast and shoot
>situation.  What have I missed?

The difference is on the order of two or three hundreths of an inch, at
least for the scenario I just ran. I used the full formula, with the focus
distance as the average of the near point and far point.  The original idea
was to provide an alternative to the 1:30 rule that was quick and easy.
It's not precise, but again, one helluva lot closer than 1:30.

>Why'd Tom use inches instead of metric in his distance numbers?

My original was in centimeters, since the math is easier that way, but I
translated into inches for the Americans in the crowd.

I have constructed a simplified Excel version in several formats, and will
put it on my FTP site tomorrow.  Complete with instructions and stuff.  You
could easily change the formula to set the focus at the neaar point.  And I
forgot to ask, how is your Weltanschaaung?

>PS - My Weltanschaaung is much better now, thanks for asking.

Cheers,  Tom



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