Re: Focus corrected IR-filter (was: Another New Subscriber

["Willem-Jan Markerink" <w.j.markerink@xxxxx>]

On  8 Dec 96 at 20:23, Steve Midgley wrote:

> I have to admit that I was basically echoing the info in the Rollei
> "Practical Accessories" publication. I used to manage a used camera shop
> that specialized in Rollei and we were doing research on just how practical
> some of these accessories really were. We did put a micrometer on one of
> the larger size IR filters (Bay IV or VI, can't really remember) and did
> find that it was very slightly thinner in the center if I recall. Not
> exactly scientific in any case. Though the shop doesn't exist, the
> inventory does - maybe I'll see if I can repeat my results and report back.

A micrometer was the only thing we didn't try, but if you pick a 
clear sunny day, and throw the reflection of the sun on a far wall, 
that image should not stay the same size, both sides of the filter, 
on various distances. It *did* in our case....

I also wonder why Rollei offered this filter in the first place, as
I don't think there ever was a true deep IR film in 120 format, they
all were at the level of Konica. Even the HIE predecessor of those
days was not a deep IR film. 
And the color of this filter also doesn't warrant a full IR
correction IMO....it is not even opaque (another indication that the 
films it was ment for were not deep IR).

--
Bye,

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      The desire to understand 
is sometimes far less intelligent than
     the inability to understand


<w.j.markerink@xxxxx>
[note: 'a-one' & 'en-el'!]

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Topic No. 18