Re: M6 Camera strap and Quick Lens Test

["Henning J. Wulff" <henningw@archiphoto.com>]

>     I am really excited.  I just purchased a new M6 and used 50mm f1.4,
>     and 90mm f2.  What a marvel of craftsmanship!
>
>     The first thing to do for a newby like myself is to get a camera strap
>     and test the used lens.
>
>     Would any of you please recommend a high quality camera strap that
>     will do a good job of protecting the camera from scratches at the lug
>     connections and be very comfortable on the shoulders and neck and be
>     discreet and unobtrusive.  I have used a leather wide strap with
>     leather protectors at the lug connections on my Nikon but I can't find
>     a manufacturer name on it.  Is the new neoprene(?) material the way to
>     go?
>
>     Also, any recommendations for a quick test of lens for any defects,
>     etc.?

Re: camera strap -

Domke makes some nice ones, and has the little leather bits. I tend to use
the slimmest with the least hardware. It doesn't slip, is pliable (the new
Leica ones have a fairly stiff shoulder pad) and is more comfortable if you
get hot and sweaty. Also cheaper.

Re: lens test -

There are two sets of criteria; physical function & appearance, and optical
performance. For the first, put it on a camera with a viewfinder you know
is adjusted correctly, and check infinity focus (and smoothness of focus
mount). It should focus to infinity exactly. Look at the diaphragm blades
to check for oil. This can be cleaned, but costs. Also if there is oil, the
lens has probably been in some hot area for a while and some oil may have
evaporated and been re-deposited on lens elements. Check for scratches on
the lens (be cautious about a lens that has scratches on interior elements
which indicates that someone botched a repair. Look throught the lens at a
bright surface to look for obvious haziness, color casts, separation of
elements and shininess at the edges of elements or other interior parts of
the lens. Also use a flashlight to look inside the lens for reflections off
the edges and haziness on the surfaces of elements. Obviously, some of
these tests are not really relevant to new lenses.

Optically, a quick test involves the use of slow film, Velvia being a good
choice. As most of the test involve opening the lens up as much as
possible, a tripod is not really necessary if testing lenses such as a 50
or a 90. If you always use a tripod, use a tripod for tests. If your main
subject of interest in photography is brick walls, test your lenses on
brick walls. It is usually best to shoot pictures like you would normally,
because you have to be satisfied with the lens under your personal
conditions. Again, use a properly adjusted camera body.

 If it is so cloudy out that Velvia at f/2 will not give you 1/125sec
(happens often here during the rainy season), use a faster film or a
tripod. Velvia needs f/2.8 at most on a sunny day at 1/1000sec at long
distances, depending where in the world you are. So to test your lens at
f/2 you might want to put a high quality polarizer over your lens for some
of the tests. It does cut down slightly on the quality achieved, but still
gives a very good indication of the lens condition, and does tell you about
variations, which are most important. Shoot at maximum aperture; exact
exposure is not essential, but it should be close. Set the lens at
infinity, and pick an item suitably distant (for wideangles this can be
closer; for long teles it might need to be a couple of miles away. This
item should have some strong colors, with sharp edges, and fine detail. A
sign is often very good and available.

Take five shots, and put the object in the center and in each corner. These
should all be at the same exposure. Then shoot the same target at the next
two smaller stops. Then find a target about 20 feet away (for a 50 or 90),
and do the same, and then at 5 feet. With the latter, maintaining the
correct subject to film distance is especially critical, and may not be
easily achievable. The problem is the geometry of the situation, as with a
50mm lens you would have to back off 5.37 inches when placing the same
object in the corners as you focussed on at 60 in. when the subject was in
the center, assuming that your lens has a flat field (which the Summilux 50
does not, at closer distances and larger apertures). So the closest focus
test does not tell you much about the corners.

Check the slides with a good magnifier (the 50 Summilux works in a pinch).
At infinity the center should be very sharp at all apertures with slight
improvements as you stop down, and the corners should show increasing
sharpness, contrast and color separation as you stop down. The main thing
is that the corners are all the same at any aperture. If a lens has been
mistreated in any way, or assembled by someone with a serious hangover, the
corners might show varying performance. There are a lot of other tests for
flare, color balance, optical and physical vignetting and basic optical
ills, but usually if the corners are equal and not too far off the
performance of the center in the general range of 50 times the focal length
to infinity, then the rest of the performance will be up to factory specs.


   *           Henning J. Wulff
  /|\     Wulff Photography & Design
 /###\      henningw@archiphoto.com
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