----- Original Message -----
From: <ReinholdLetschert@xxxxxxxxxx>
To: <olympus@xxxxxxxxxxxxxxx>
Sent: Thursday, September 19, 2002 9:27 AM
Subject: [OM] re: lens hoods/suitablity/shapes
> Following the discussion on suitabilty of hoods to lenses and
> shapes of hoods, I remembered some good advice that I got from a
> good friend of mine (a professional photographer) when I was still
> a student and always grabbed anything cheap with a M42-mount
> (long before OM) and which never had a suitable hood:
>
> -Get a light box (for sorting slides) and a sheet of grease proof
> paper.
> -Put the camera with back removed on the lightbox (back to glass).
> -Mount whatever you think is a suitable hood to the lens, open the
> lens to the maximum f-stop and put it in infinity postion.
> -Open the shutter in "B"-position with a cable release. Put the
> grease proof paper (or any suitable matte screen) flat on the hood.
> -When you switch on the light box you will see a spot of light
> shining through camera, lens and grease proof paper (you might
> have to cover the rest of the lightbox, which isn't covered by the
> camera, to avoid getting dazzled by the bright light).
>
> - when the front diameter of the hood is slightly bigger (2-3mm or
> 1/8") than the projected light figure on the sreen your hood is ok
>
> - when the light figure is cut by the hood its angle is too narrow
>
> - when there is plenty of room between the light figure and the rim
> of the hood it is too wide
>
> As to shapes of hoods:
> When you experiment with different lenses in the above mentioned
> way on the light box, you will find different figures of projected light:
>
> fully opened:
> wide angles tend to a rectangular shape, sometimes also pin
> cushion
> tele lenses from about 100mm on (for 35mm) tend to a circular
> shape
>
> when you stop down to f8 you get rectangular shapes from wide
> angle to roughly about 300mm, the projection of longer focal
> lengths still tend to be round
>
> ergo: rectangular is not always better
>
> I never looked at zoom lenses that way, so I don't know anything
> about them.
> Unfortunately these experiments don't work with digicams :-)
>
> Also: when you use lenses with extension rings or in the bellows,
> the effective opening angle of the lens gets narrower. Thus it might
> be useful to use a hood that is narrower than the standard one.
> That's why some pros use bellows-hoods for macro. However with
> macro photograhpy and strong side light sometimes the ONLY
> thing that helps is one ore more pieces of dark cardboard to get rid
> of strong reflexions.
>
> ---
> Reinhold
>
Every time I think the chatter on this list is going nowhere, a posting like
this comes along. Great one Reinhold. I have learned so much from postings
like the above.
Michael.
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