T3D Re: Film plane mark on SLRs

[Tom Deering <tmd@xxxxxxxxxxx>]

>This is useful, because when a recent P3D discussion of how to
>implement the Spicer/Bercovitz formulas was under way, Tom Deering
>assumed, as I did, that this advice to measure from the film plane was
>applicable to the main discussion - how to get the general case math
>into *practical* use.


I thought I was using the illustration in John Bercovitz's "Comparison"
article, but I've been repeatedly confused on this subject, so I certainly
could have been wrong.

Having two different ways to measure object distance *is* confusing. Plus,
the techies and the non-techies both feel their way is self-evident, so
it's not well explained.

Glad we have that old question answered.

Thanks,

Tom



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