Also don't forget that this works the other way too. The hoods for 28mm are
different. If you use a 2.8 hood on a 2, it will vignette.
BTW I happened to put the hood for 35 - 70 F4 next to one for 35 - 105 the
other day, and I couldn't tell the difference! I wonder why they were and still
are sold separately?
Julian
> from: dreammoose <dreammoose@xxxxxxxxx>
> date: Mon, 16 Sep 2002 22:27:57
> to: olympus@xxxxxxxxxxxxxxx
> subject: Re: [OM] Info/WTB Lens hood for the 35-70mm f3.5-4.5
>
> Remember that both diameter and the distance from the front focal node
> in the lens to the front of the hood determine the angle covered. Thus,
> two fairly close focal lengths whose front nodes differ in their
> distance from the hood mounting point the right direction (by chance or
> by design) could indeed both use the same hood as the theoretically
> correct hood. Whether Oly did this or not, I have no idea, but it's
> possible in cases like the 35/2.8 & 50/1.4.1.8s and the 85/2 & 100/2.8.
>
> The problem with rectangular and tulip hoods is alignment. Unless you
> design a bayonet mount that only allows correct orientation, as Oly did
> with the 35-80/2.8 and other manufacturers have done, people do silly
> things - like rotate the hood rather than the camera for portrait
> orientation. I know none of you excellent Zuiks would ever do anything
> so silly, but I can somehow imagine myself bumping a slip-on or screw in
> hood and not realizing that the rectangualr orientation is askew until
> after taking the fleeting image that will now be vignetted.
>
> Moose
>
> Jim Brokaw wrote:
>
> >I've noticed that Olympus sometimes uses a hood for more than one focal
> >length... <>
> >
> >Rectangular hoods seem like they would be closer to ideal than round hoods,
> >if you imagine the image-forming light rays as a four-sided pyramid with the
> >tip inside the lens at the nodal point, then a four-sided hood should be
> >able to give better stray-light protection without vignetting. But for many
> >Olympus lenses, the hood is round (which has to be a compromise in the first
> >place) and then also covers the 35mm and 50mm focal lengths, which means it
> >must be less effective to the 50mm focal length than it could be... or it
> >would vignette at the 35mm focal length.
> >
> >While I know in practice the effect is probably minimal, why didn't Olympus
> >make dedicated hoods for each focal length, and even better make them
> >rectangular hoods? With a zoom you're still stuck with shading the widest
> >focal length best, except that Olympus cleverly worked around that for the
> >35-70/3.6 hood... seems like they could have done more for the rest of the
> >lens hood range.
> >
>
>
>
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