No, the distances were not arbitrary. If you go back and read my
original post on this subject and (I think) my last comment, the
distances were chosen such that an error of 1 meter in focusing would
alter the total DoF by a considerable amount. From 5 to 6 meters on the
zoom at 24/3.2 the DoF gets extended by 5 meters on the long side. It
was intentionally sized to say you can't claim extra DoF for the lens
since, at that distance, you can't focus accurately enough to say they
were actually focused at the same distance. If you can't claim exactly
the same focusing distance (within a given error range) you can't claim
unusual DoF behavior on the part of the lens. I still maintain that's
the case but neither one of us has proven a case. I can't since I don't
have the equipment.
Chuck Norcutt
Ken Norton wrote:
> Just as a point of playing around, the split-image focusing aid in the
> OM-3Ti gave me the ability to EASILY focus on the three points. I
> suspect, however, that the focusing isn't that accurate as this would
> require a level of precision in the mirror and focus screen position
> which is greater than manufacturing tolerances would allow.
>
> I recon I could reshoot this with the altered goal-posts, but figured
> that your 5.5, 6.0 and 6.5 meter distances was arbitrary anyway, so I
> did my own thing.
>
> AG
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