>"Chris T. Daida" wrote:
>>
>> Why?
>Because they were sturdy, metal and rectangular for maximum coverage!
>
>Mr. Bill
I always thought that a rectangular hood will be optimal. But I made some
calculations and found that it's not true.
It's true that the film format is rectangular, but the lens itself is
circular. So, the optimal solution is not round or rectangular.
I have found that an optimal rectangular hood will need to be longer in the
corners (diagonals). It will be the reverse of a petal shaped round hood
that is longer in the vertical and horizontal directions than in in the
diagonal directions.
Now, I design muy own petal shaped hoods. I like Do It Yourself things.
In fact, the important point in a well designed hood is its length. The
longer the hood, the better it is. So a petal well designed petal shaped
hood is better that a rectangular one if it is longer.
My favourite hood will be round petal shaped, in order to be easily packed
with the lens in reverse position. Made of metal or plastic, with internal
anti-reflective material. Connected to the non moving parts of the lens, as
most Canon ones do, and with a rubber end in order to absorb small bumps.
Unfortunatelly I have nor the tools, nor the materials, to build such hoods.
Telescopic hood for zooms will also be very good, as zoom hoods are optimal
only for the wide focal length. I think of a telescopic hood for a 70-210
coupled with the zoom position. That will be great!, but will also be
expensive :-(
The hood of the 28-135, for instace, is a very bad one for the 135mm
position. A cheap, collapsable rubber, standard 50mm hood, will be better
in this position.
Best regards
Vicente
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