On 7 Mar 2001, at 10:28, Bojidar Dimitrov wrote:
> Having just spent all of 60 seconds thining on this topic, and having done
> no experiments, my gut reaction is to disagree. The "tulip" shape is due
> to the fact that we are trying to cut out the potions of the light cone
> that are outside of the rectangular film frame.
>
> I think that you will agree: it is better to use a tulip-shaped shade than
> another shape that is the result of taking a tulip shape and cutting the
> four "protrusions." This is the longest that a shade can be (at the givne
> angle) without causing vigneting.
Absolutely true for a fixed lens, the tulip shape is derived mathematically as
a function of the principle points vs the lens AOV and if designed properly will
provide the most comprehensive lens shading possible without causing hood
induced vignetting
Any shape of hood is generally a compromise on a zoom as it has to
accommodate a varying angle of view, you can't zoom the tangs on a tulip
hood.
Cheers,
Rob Studdert
HURSTVILLE AUSTRALIA
Tel +61-2-9554-4110
Fax +61-2-9554-9259
UTC(GMT) +10 Hours
[EMAIL PROTECTED]
http://www.ozemail.com.au/~distudio/publications.html
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