Re: More on UV photography

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

On 12 Mar 99 at 9:53, Rolland Elliott wrote:

> > "Third, M39 is by far the most universal mount on this
> > planet.... 'but':you most likely loose infinity focusing with all
> > (35mm!) photo lenses, as
> > well as with all non-tele enlarger lenses (less than 75mm or so is my
> > rough guess)....but for macro use this is all you need.
> > So, this leads to the famous 'last but not least' question for
> > non-bellows use: what focal length are we talking about
> > here?....what is the focal range of these EL lenses?"
> 
> Nikkor EL lenses range from 40mm f/4 to a 360mm f/5.6 lens, quite a
> wide variety.  I tried hand holding a 50mm f/2.8 lens infront of the
> lens mount last night and discovered that I could get sharp focus on
>  objects about 2.75 meters away, but no infinity focus. I just bought a
>  75mm f/4 and a 135mm f/5.6 lens on ebay for a pretty good price, but
>  have yet to use them.

Mmm....what format are those Nikkors made for anyway?
Larger than 24x36mm negatives?
It just occurred to me that with a little luck you could do
medium-format tele work with the longest focal lenghts...
Are they by any chance also well-corrected for IR?....:-))

With some approximately-matching extension tubes, an
M39->medium-format adapter, and a focus-rail camera like Mamiya
RB/RZ, you would at least have a medium format solution for
artificial-light situations (since RB/RZ have lens shutters)....even
better would be a Rollei 66, also focus-rail, but with focal-plane
shutter (so daylight short shutter speeds also included).

>  You must be one lucky guy!  Those 18A filters cost a mint.  

The guy who sold it to me claimed US$200 new, in Holland....is that 
close?....:-)) 
I even bargained a bit on all 3 items, IR-book, IR-filter and 
UV-filter....hey, I am Dutch, it's in my genes....:-))

> What exactly is a homebrew Scott UG1/UG3 filter?

B+W 403 and 484 respectively....a friend found them as unmounted
circular's, and they now sit in 49mm rims (I think, can't use them
directly on any of my lenses, only held in front of my 100/2.8
macro).....see the chart about UV/IR filter transmission and their
equivalents on my homepage:

http://www.a1.nl/phomepag/markerink/mainpage.htm

>  While your working on your UV web page chapter you'll probably want to
>  note the following facts:
>  1) Tiffen makes an 18 A filter

Interesting, didn't know that (the #87C isn't that often used either, even 
though it is listed in B&H tables).
Wouldn't surprise me if both Kodak and Tiffen use Schott UG1 or 3 as 
well....it's quite an exotic piece of glass, even for scientific 
use/customers they are apparently not easy to get.

>  2) B+W no longer makes its 484 filter, which I believe  is equivalent
> to a 18A. 
> They do however still make a 403 filter which lets in UV and some
> visible violet light, but not much.

Will try to find out with both B+W and Heliopan....I vaguely recall
that at least one of them is not unwilling to do custom-work, and
Schott definately still makes this glass, and that is what they were
using in the past....probably just a stock- or market-related issue.

But none of that will change the stiff price of these filters....;-((


--                 
Bye,

Willem-Jan Markerink


      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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