[Leica] Unintended flare test of 90mm Elmarit-M

[oliverbryk at iqmail.net (Oliver)]

As requested I have added a few images from the same event and roll for
comparison purposes. They are:

http://gallery.leica-users.org/OliverBrykPhotos/04Aug02_01c : the same frame
as #1, scanned as 48-bit RGB at 4000ppi, resized to 1024 and converted to
JPG;

http://gallery.leica-users.org/OliverBrykPhotos/04Aug02_34 : a different
frame, with a touch of flare;

http://gallery.leica-users.org/OliverBrykPhotos/04Aug02_11 : a frame shot
from the same position as #1 but at a different azimuth angle.

I am grateful to everyone who has offered an explanation for the flare. I'll
summarize them below (my apologies for any oversight or mis-quoting - no
slight is intended):

1. "does the flare show on the negative?" Yes, very noticeably.
2. "Think back and see if you can remember coming out of an air conditioned
space just before this pic was taken. It looks like condensate to me, not
flare. I have 2 of these lenses (black and chrome) and find it quite flare
resistant. Strangely enough, my late (1990) German TE doesn't flare either."
and "Looks like condensation fog. Maybe you got out of AC into a humid
afternoon? It happened to me recently, where the first few shots of a series
were fogged, and then it cured itself. One shot was shooting down away from
the sun." I remember such conditions from having lived in DC; San Francisco
is blessed with a relatively cool climate.
3. "something in front of the lens (finger...strap...leaping child?)" I
think getting either the strap or the finger out in front of the 90 is not
likely (although I've done it with the 35 on my IIIa). The leaping child
hypothesis is interesting. As a former subscriber to "The Journal of
Irreproducible Results" I estimated the coefficient of reflectivity and the
surface area that would be required to produce this effect. I concluded that
a the head of a hairless albino would have to be so large that its mass
would prevent the child from leaping.
4. "This happens when direct sun (not in the frame) hits the lens obliquely.
Most if not all lenses will do this." Clearly a possibility, even with the
built-in lens shade extended.
5. "...on close examination, this alleged flare squarely occupies the middle
fifty percent of the frame and seems to stop at a fairly straight line
before the top of the frame.  I own a Skinny Tele-Elmarit, so I know flare.
This doesn't look like any flare with which I am familiar...too many
regularities. Oliver, do you know if you have the telescoping shade fully
extended?" I usually do but I could have pushed it back inadvertently.
6. "...Look behind the tree in the center background of the picture. There's
a car there with a windshield that could have reflected sunlight directly
into your lens at the instant of exposure. The focal plane shutter may have
passed at prercisely the wrong time and the car 
will have moved forward a little when the slit passed and registered the
image. The windshield is awfully bright even so. IOW, because the car was
moving, the reflected light would be registered BEFORE the image of the
car........ the result of a focal plane shutter." An intriguing idea. That
day I shot most of the time at 1/250 or 1/500. Would the car be going faster
than the 25mph limit ;-) ?
7. "I have owned and used two 90 / 2.8 lenses. One was the skinny version
and the other was the latest version. ...I have found both to be flare prone
even when shot slightly in angle to the sun, and at an angle in which my
other Leica M lenses would not exhibit such behavior. I believe that other
users would differ in experience. As for me, I would not want to buy and use
another 90/2.8 again." 
8. "It does not look like flare to me. By the way, I had the current
Elmarit-M 90mm/f2.8 and found it quite flare resistant. I shoot a lot in
color, and I find color photography is more demanding of lenses in that
regard."
9. "I think this happens because just-out-of-frame light sources create a
light patch on the inside of the barrel which shows up as a broad flare
patch on the film. You can see the effect with the lens off the camera,
pointing slightly away from the sun. My 50mm Summicron does this as well:
http://www.leica-gallery.net/beddoe/image-40304.html "
10. "To me, it looks like a light leak, preflashing the film, from changing
the lens in open sun." I did switch several times between the Elmarit 90 and
the Summicron 35. I'm usually careful to change in shade or at least shield
the camera with my body. I could have been negligent that day...

I really appreciate everyone's time and thoughts. Where do we go from here?

Oliver