Re: [Leica] Re: Halogen light and lenses

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

Gary Whalen wrote:

>    You are obviously a "hell of a man".  You don't need to test but you just
>shoot.  Thats great for you but if it is true you are sure wasting a lot of
>money.  Why buy Leica if your not getting more than Nikon or Canon?  Why
>bother.  Their is an inherent obligation of Leica to make sure the lenses and
>bodies are perfect.  At least as perfect as possible.  My point is simply
>this:
>if the lense is delivered in a condition LESS than it should be then why?
>Why
>accept it?  Why ignore it?  Do you do the same with your cars, house, stocks,
>shirts, shoes, picture frames, etc.  You have to inspect your stuff if for no
>other reason than to keep Leica up to its own high standards.  If checking
>expensive equipment for flaws is stupid then I have some land I want to sell
>you.

Here is the new mantra: THE SPECKS DO NOT MATTER. PICTURES MATTER.

Seriously, this discussion is about as meaningful as saying that the new
Rolls Royce Seraph is a shoddy piece and BMW should be ashamed of
themselves because that new Rolls I saw yesterday on the lot had some dirt
in the wheel wells. Actually, a lot more dirt than I ever saw in any Leica
(or Holga.

Lenses (and cameras) are assembled in 'clean room's. Not as clean as chip
manufacturers' rooms, but 'clean'. There is no absolutely 'clean' room,
there is no 'perfect' lens, but Leica makes an effort to hit a certain
price/quality point and is reasonably good at it. Since it makes no
difference to the final image, and would make a difference to the price,
'cleaner' rooms are not used. Even a chip manufacturer has a certain
tolerance. When he gets to a certain number of defects per unit, he does
not try to get 'cleaner', as the cost benefit is not there.

Lenses for general photographic use are not hermetically sealed. When a
storm comes, and the weatherman says that a 'low' is here, it means that
your lenses have sucked in some outside air, along with some specks of
dust. Not only that, but various previous specks that have been floating
around in your lens have moved, including those that you knocked loose last
time you took your camera on an airplane ride (where the air pressure is
low and the vibrations high). In that hot summer dry spell, the lens
exhales. Lenses with floating elements wheeze every time you focus, and
let's not forget zooms!

If you want to test this, take a 50mm lens, and put on a cheap filter. Take
some pictures at various apertures and distances. The quality will go down
slightly from no filter, but not by a big amount. Now make a black mark
(about 10 times the diameter or 100 times the area of a typical 'speck'. I
assume speck watchers have measured their specks, and have a properly done
size, frequency and radial distance curve of their specks at hand :-). Now
take some more pictures. Now make the speck 100 (10 000 x the area) of the
average little speck. Take some more pictures. If your speck covers a
sizeable fraction of the taking aperture, you will see a loss of light, and
there might be uneven illumination if the speck location is chosen properly
(If you are really doing this accurately, the speck still won't be large
enough). That will probably be the extent of the damage. Now clean the
filter, and put a small scratch (which will likely be orders of magnitude
bigger than the bright specks, no matter how hard you try to keep it small)
and take some more pictures. If the scratch is 1/10 of a millimeter wide
and 1/10mm deep and 5mm long (this will look quite big, even without
halogen) you will likely not see much difference, unless a very bright
source of light outside the picture frame is relected by a facet of this
scratchy directly onto the film. Then you will see flare. Otherwise, if you
did not know about the scratch, you wouldn't notice the effect for years.

BTW, Hasselblad lenses have little specks and shiny bits, as do Rodenstock,
Schneider, Canon, Nikon, etc. The manufacturers all play by the same
optical rules.


   *            Henning J. Wulff
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