At 1210 PM 8/24/01 -0700, you wrote
Hello David,

Lately if been wondering about comparisons of
equivelent lenses for different film formats. Do you
know of a source that will chart the data?

I'm hoping to find a table similar to the following

Film size | Angle of view | Lens
--------- ------------- ----
35mm ??º 20mm
??º 24mm
??º 35mm
... ....
... ....

645
6x6
6x7
6x9
4x5
5x7
8x10
...

Any form that the data can be arranged in would be
helpful.

Thanks in advance (& be well),
-- Jack --
===========================
Jack Daynes

I'm sure they exist, but possibly more satisfactory is making
your own table (a ruler, and basic trig. will do...). For instance,
the "format normal" focal-length is defined as equal to the diagonal
of the film image area, so for 4x5, draw a 4x5 rectangle, with a
slightly smaller one inside to represent the actual image area (minus
the film-retaining frame) - it should be about 145-150mm. For 35mm,
about 43-44mm, etc. From those numbers you can derive the multipliers
to convert from one format's lens FLs to another. With triangles, you
can represent the lens center, distance at infinity from film, and the
film size - and from that, figure the angles of view (H, V, and
Diagonal)
of various FLs on various formats (or use the multipliers for
conversions,
once you have enough numbers to do this...). Not hard...;-)