Re: Questions RE: Old, poorly stored film & B+W filter's IR Cmn

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

On 30 Jul 96 at 18:29, Adam-HALPID Klyce wrote:

>      Ladies & Gentelmen,
>      
>      Hi'ya. I am planning a trip to Yosemite next weekend and as I
>      started to pack some stuff last night I realized I have had a
>      roll of Kodak's HIE in a photo-backpack for some time. It's 
>      been in a closet but the temperature must fluctuate pretty
>      much between 65 deg.(F.) & 70 deg.(F.) I am wondering if 
>      any one else has had experience shooting HIE that has not been
>      stored very well? I have many more rolls in the freezer and so
>      I think for this trip, I would rather use something I am sure
>      about than take chances with film that could be fogged.

In one of my book I read a similar story; other than a decrease in 
overall sensitivity, all went fine.
      
>      On a similar note, I have an unprocessed but exposed roll of 
>      Ektachrome IR that I lost. I have found it and well, it's been
>      sitting in my desk drawer for about 14 months. This, in a room
>      that gets direct sunlight and fluctuates in temp. between 80
>      degrees (F.) and 50 degrees (F.) Given the cost of developing
>      this stuff, should I bother?

Normally with color film there is the risk of color shift....but
that would the least noticeable problem with EI....8-)) 

>      Also, I happen to use B+W filters, and was looking in a brochure
>      I have. For infrared they write:
>      
>      "In general, the sensitivity of black and white infrared film is
>      about ISO 50/18-degrees. Kodak infrared film and the B+W filter
>      #092 is about ISO 20/14-degree; with the B+W filter #093 about
>      ISO10/11-degrees. 

Mmm....the first complies with 25 red I guess, #092 equals 89B, and 
#093 equals 87C; and the ASA numbers fit in neat as well.
FWIW: I have made a conversion table for Wratten, Schott, B+W and 
Heliopan IR filters. 

>      However, these values are highly dependent on
>      the strength of the infrared radiation in the scene which is 
>      much higher when the sun is low than at any other sun angles...

Read that before....I think it should better read: "relative 
strength". Keep in mind that UV is at its peak shortly after noon, 
hence the amount of IR must be relatively less than early in the 
morning or late in the afternoon. For late in the afternoon one could 
also argue that what makes the horizon red (dust) could also 
influence the amount of IR....wild guess though....
Would be fun to have a spectral chart/time plot of sunlight....

      

>      ...The impressive special "wood-effect" (very bright to white
>      reproduction of chlorophyll in black and white positive images)
>      appears the strongest at low sun angles. 

IMO, this (and the above) could also reflect the fact that contrast
(read: existence of shadow) is much larger early in the morning and
late in the afternoon (the first theoretically more than the latter
due to dust), and that reflectance of foliage works better at low
angles than when the sun is burning on top of it.
A lot of guesses....comments?

>      Under such conditions, 
>      a strong red filter plus normal black and white film is 
>      sufficient. Infrared pictures without filters always produce
>      unsatisfactory results similar to black and white pictures 
>      missing tonal value graduation and color pictures showing a 
>      strong blue-green tint and little color differentiation."
>      
>      (Now, aside from the rather subjective tone of the peice (though
>      rather appropriate for a company that makes & sells filters) I
>      wonder; has anyone else noticed a shift in the strength of IR
>      at Dawn & Dusk? Is this a clue in the mystery of trying to find
>      a general approach for metering for IR film?)

I have read it before in several books and brochures.
FWIW, I also once read that spring foliage reflects more IR than 
autumn foliage....dunno what makes chlorophyll reflect, but it could 
be related to the amount of water in the leafs....or any other 
seasonal variable....any bio experts care to comment?
      
>      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>      B+W Filter #092 - (Schott RG 695) - Dark Red which filters out
>      light below approx. 650nm. Filter Factor approx. 20-40.
>      
>      B+W Filter #093 - (Schott RG 830) - Black which filters out
>      the entire visible spectrum, or below 1000nm. 
>      
>      B+W Filter # 094 - (Schott RG 1000) - This filter transmits the
>      invisible long-wave radiation in the spectral range above 1000
>      nm virtually unweakened. A pure infrared picture is the result.
>      
>      B+W Filter # 099 - (Schott OG 530) - Orange, blocks the blue &
>      blue-green portion of the visible spectrum up to approx. 500nm.
>      
>      Hope some of that was of interest. I do not work for, or know 
>      anyone who works for, B+W or Schneider Kreuznach and this does
>      not constitute an endoresment.

Neither do I, but I have put a lot of their stuff on my homepage.
Should I bill them?....8-))

Serious, I recently also got a numerical brochure for Schott glass
filters, so I could list a similar range of filter spectra as is
currently available for Wratten (the chapter originally typed in by
Andrew Molitor). 
Are there more people interested than just me? Or is this a tough
typing exercise in vain?....;-))


--
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. 10