[MF3D.FORUM:424] Re: fl/30

[Greg Erker <erker@xxxxxxxxxxxxxx>]

>    But the question that arose earlier.....that is still not clear to me is
>this.... if your formula is accurate than I guess the answer to the
>deviation question must be..... the deviation does not change even when the
>fl of the camera lens is increased or decreased.  A few posts ago, it was
>suggested that when you double the camera  fl, you halve the deviation?  But
>on the other side of the coin, when you go to shorter fl camera lenses you
>should never go below 2.7 deviation. When using longer fl lenses this logic
>appealed to me, hence why I am pursuing this one till the bitter end :-)

  If you are always viewing with the same lenses
then you want the on-film deviation to be unchanged
(2.7mm for MF w/ 80mm viewer lenses) when you change
taking lenses.

  If you are changing the viewing lenses to match
the taking lenses then the OFD (in mm) needs to scale so
that the angular deviation you view remains unchanged.
So if you take with a 50mm lens and then view your
MF with a 50mm lens you need to scale the 2.7mm OFD
to 1.7mm to avoid eyestrain due to excessive angular
deviation when viewing.

My understanding - Greg E.