RE: [Leica] focus inaccuracies: my test results

["Dan Honemann" <danh@selectsa.com>]

Henry,

> 2.5 feet = 30 inches (where you state it works OK)
> .7 meters = 27.3 inches (Leica claims is min focus distance)
> so it seems there is a 2.7 inch difference in where it focuses correctly
> and where you hit trouble.

Actually, the min. focus distance specified for the 75/1.4 is .75 meters,
which is roughly equivalent to 2.5 feet, the last distance mark printed on
the lens.  But the focus ring actually turns beyond that by half an inch
(measured along the perimeter of the barrel), which results in the actual
min. focus closer to 28 inches, or nearly two inches closer than the
published min. distance (.75 m = 29.5 inches).

I'd consider that to be an oddity with my 75, but in fact all of my Leica
lenses do this.  Both the 35/1.4 asph and 50/2 (current version) focus down
to 25.4 inches with the ring turned all the way clockwise, or two inches
closer than spec'd.  What's different about these two lenses is that they do
focus accurately at this bare min. distance--and the difference can't be
accounted for by DOF, as I am measuring the point of focus in every case as
1/3 down the in focus range on the ruler.  Trust me, it is _very_ evident
that the 75 is off but the 35/50 are on.  It is also quite evident that all
three lenses are off on Hexar RF at this distance.

> This is what SLRs are for.
> OTOH carrying one extra lens is easier than a whole nother camera system.

And we pay a premium for quality engineered equipment for the sake of
precision.  It IS obviously possible to have rangefinder/lens pairs that
focus accurately throughout the focus throw as proven by my M6 + 35/50
combinations, and no doubt the vast majority of those owned by LUGgers.  In
the Leica world, this seems to be a problem specific to the 75 (others have
noticed it as well)--or at least the current batch.

In the Konica world, it may be a problem with the RF alignment on my
particular Hexar, and hopefully it will be fixable.  I've only gotten the
one piece of feedback from Jeff who says his Hexar does focus accurately
through the entire range on his 35 summicron.  Other Hexar RF owners may
want to test this out on their cameras before doing much shooting at the
min. distance wide-open.

Dan