Re: Questions/Intro

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

On  2 Sep 96 at 18:54, Jeff Spirer wrote:

> I am new to the list and have a few questions.
> 
> 1) For IR, I normally use HIE in 35mm, but my lab recently gave me Konica
> 750 in 120 format.  The sheet is in Japanese, Konica's web site ignores IR
> film as far as I can tell, and I just can't find the info.  Questions are
> what filters with what general EI range.

Mmm....32 ASA to start with; +3 stops for red #25. Not sure about darker 
filters, seems as if #87 is the darkest usable filter, but you get 
fractions of ASA (or negative DIN....8-)). #89B is a nice compromise, 
I guess +4 or +5 stops total should do.
Did you check the FAQ? (not sure how many filters are in it)
 

> 2) For my Rollei (TLR), the only red filter I have is the standard one for
> b&w work despite looking everywhere for a Rollei IR filter.  (I did find
> one but the price was ridiculous.)  Also, the Rollei IR filter is opaque
> (one reference says the type for the opaque filter is Agfa No. 83) and I am
> wondering if this works with Konica 750.  Also, what type the "normal" red
> Rollei filter is would be useful information.

Darn, another number not in my filter reference books. I do have a 
#82 gelatine from Orwo which is also not listed. Neither 
#82 nor #83 is listed in my references (which includes an antique 
Wratten catalogue from 1928, and a modern Kodak handbook)
The Rollei filter I have resembles a #89B in my opinion, and beware, 
it is not opaque, you just have to adapt you eye to the light level, 
and look at a bright sun lit scene. It is transparent enough to use it in 
front of a lens. 
 

> 3) I have an old Rollei brochure that came with my camera that has an
> interesting statement: "To compensate optically for the required focuing
> difference, the infra-red filter is ground to act as a weak lens."  Bob
> Salomon is unable to locate any confirmation that this is true - I even had
> to fax him the page from the brochure.  Does anyone have any info on this?

How long ago did he start research on this? We did have a thread on
this in the Rollei list a few months ago.... In his defense I must
say that even Rollei Germany can't confirm this. Even *they* didn't
know about this quote....I also got this info sheet included with
the lens (albeit I can't be 100% sure lens and manual belong
together). Joe Berenbaum pointed me to the filter in the first
place, by quoting some Rollei literature....the chairman of the
Rollei Collectors Club Holland, from whom I bought the filter,
couldn't confirm it either, and according to a friend, an optics
freak: the filter does not have any diopter build in. One should be 
able to tell whether it contains a diopter by reflecting sunlight to 
a distant wall. If the circle is as large as the filter itself (try 
both sides!), then it does not contain a diopter. 
However, Rollei Germany did confirm that such a filter (and it's 
production) was certainly possible, albeit with a price tag (they quoted 
a rough DM 400). They also thought a diopter of 0.10 was 
required....not sure about that. 

 
> 4) So finally, if the above is in fact not true, since the Rollei does not
> have an IR focusing mark, what is the preferred method for focusing a
> Rollei with IR film?

Refocus to the f5.6 or f8 mark, focusing towards the lens (away from
infinity). For a bellows camera, you can also use 1/2% of focal
length as additional extraction.

--
Bye,

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The difference 
between men and boys
is the price of their toys

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

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Topic No. 16