Wayne wrote:
>While we're on the subject of lend hoods, has any lens maker ever madea
>"zoom" hood ? To be effective the hood for a zoom has to be the correct
>length for the selected focal length. It seems like the internal
>mechanics of a zoom are complex, it shouldn't be too difficult to build
>a hood which zooms at the same time
And Hans wrote:
>I believe last year I read a review in one of the Dutch photo magazines
>on some new zoom lenses where one of them indeed used such a zoom-hood.
>I think it was the Tamron 28-200 AF (this lens is recently also
>released in an MF version, btw, attachable to OM with the adaptall
>mount).
Don't know if this has already been covered...
Sigma has or had a 28-70/4 zoom that worked in such a way, that when zoomed
to 70 mm the front lenselement(s) moved back into the lens and vice versa
when zoomed to 28 mm. The hood was clamped on a rim outside the lenscombo,
thus having a fixed position. Voila, a zoom with fully functional lenshood
at all focal lengths.
Unfortunately it didn't seem to be a particularly solid construction, at
least not in Sigmas rendering. My friends example, on a Pentax K1000 after
an indeed VERY dusty hike down and up the Grand Canyon broke totally in 6
different pieces. My 35-70/3.5-4.5 on my OM4 was alongside all the time,
exposed to exactly the same conditions with absolutely no problems (and
still works fine).
The whole lens seemed to be assembled completely without any screws, just
modern plastics clamped together, hard for us Zuikoholics to believe, but
true! When exposed with the fine, red dust of the Canyon, disintegration was
inevitable.
Having seen this disaster with my own eyes, I now know there ARE facts
behind the rumours of Sigma lenses falling apart.
Eventually my friend never repaired the lens, stating it would be a waste of
money since it would probably fall apart again.
I'd definitely stay out of Sigma's.
Ulf Westerberg
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