At 19:17 6/6/99 , Brian P. Huber wrote:
>The simple reason that SC lenses weigh more is because there are more
>reflections inside a SC-coated lens. MC-coated lenses allow the light to
>pass through without bouncing around. All those reflections in the SC lens
>cause the light to stay in the lens longer and it will then weigh more with
>a SC lens. On a really long lens this might add up to 30-40 mg., easily the
>difference in published weight. If you are taking photos in red light
>(George S.?) the lens would be even heavier since red light has a longer
>wave length. On the other hand, blue light might stack up more in the lens.
>Hmmm, I have to think more on that one! Could someone help me with this?
>
>This SC-MC question can also be verified by disassembling the lenses and
>weighing the various components. An excellent lens would be the 35mm shift.
>Then, reassemble the lens without the components, weigh, and then
>reassemble.
>Olaf just got a good buy on a 35mm shift, perhaps he could help us out since
>he's also had experience taking lenses apart.
>
>Brian P. Huber
I think what is happening here is a difference in how the experiments were
conducted. When I weighed mine, it was with the front and back caps on the
lenses. Since they were all the same types of caps and the difference was
dramatic enough, miniscule (at least 2 orders of magnitude less than the
mass deltas) variations in cap masses would not change the results.
I would be willing to guess that Brian removed the caps to eliminate any
mass variations in the caps. This admitted trillions upon trillions of
photons into the lens. Since they are more easily trapped inside an SC
lens, this was enough to make them more massive than the MC lenses which
would trap far fewer photons.
In order to replicate Brian's results I removed the caps from my two SC
lenses and they became more massive, especially in bright sunlight.
As to a red versus blue hypothesis . . . I would expect since the blue
photons have more energy (but not more mass) this would cause greater lens
vibration than the red photons. This could be the cause of what was
thought to be mirror slap vibration. An experiment with red and blue
filters may be appropriate to see if a red filter increases resolution over
a blue filter or no filter. Of course this could also explain why my
distant scenics have greater resolution using a UV filter . . . it reduces
lens vibration caused by even more energetic photons in the UV region above
the visible spectrum.
-- John
P.S.
Got a couple of covered bridges for sale. Photographed them this weekend
for the multiple listings. Anyone interested? More seriously . . . also
have a truly like-new (in the box with packing; used once to make sure it
was good) Kodak carousel projector zoom lens (102-152mm) . . . since I
already have a zoom for the Ektagraphic projector I don't need this one.
If anyone is interested contact me off-list.
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