Re: Adjusting older cameras to focus IR

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

On 21 Apr 97 at 16:34, Dwight Shackelford wrote:

> Hi folks.  I'm brand new to the list, and just about brand new to IR.  I
> have some old Yashica TLR's, and a Crown Graphic 4x5 with some ancient
> lenses.  What ratio, and in what direction, should I adjust these
> cameras to focus IR?

1/4% of focal length as a rule of thumb, and you need to focus 
closer, away from infinity. 
I recently obtained a Speed Graphic 4x5 with a good working focal plane 
shutter, but without back panel nor lens. I intended to hack it to 
accept extreme wide angles (up to medium format fisheyes, transformed 
into circular fisheyes on 4x5"), but other than the missing back 
panel, it looks to darn nice to hack the bed.
If anyone has a 4x5" Graflock back panel gathering dust on his/her 
shelf, or a broken parts donor camera (don't need bellows nor bed, 
only a good working focal plane shutter and back), I will give it a good 
home....;-))

Btw, I am still a bit confused about UV focus correction....I recall 
a recent note about focusing further away, towards infinity....but 
this largely depends on the type of lens IMHO....with some types 
(achromat), the situation with UV is identical as with IR: you need 
to focus closer, away from infinity.
Check the note from Andrew Davidhazy about lens types and focusing 
(where we also got stuck with this UV-beyond-infinity focusing, as 
some lenses won't even allow that mechanically) on my homepage:
http://www.a1.nl/phomepag/markerink/mainpage.htm


-- 
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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