Re: cokin filters

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

On 20 May 97 at 20:28, Jaap Los wrote:

> Subject: Cokin filters
> 
> Hi, all!
> 
> I'm going to be crazy on IR and HIE. The more crazy I get the more
> questions I have. Here are some:
> 
> I use B+W 092 filter (similar to Wratten 89B). As I have only one such
> filter and use various lenses (no zoom!) I have to screw on and off
> every time. Moreover the filter is so dark, that I can not compose the
> picture through my reflex viewfinder. So this also means screwing on and
> off. I therefore want to use my Cokin filter holder A or P type. I have
> such a holder and adaptor on every lens. I simply have to slide the
> square type filter in and out.
> 
> My question is:  as far as I know Cokin has no filter similar to 092 or
> 89B  to fit their holders. Is there an other maker of square type
> filters 092/89b/similar that fit the Cokin holders? 

Yep, but you enter the world of custom order nightmares. I found a 
solution, see URL below. I recommend the P-size btw, although I have 
supplied a friend with a A-size #87C in the past. The P-system is 
simply more versatile with future expansions into wide angle, large 
aperture and medium format lenses.
Of all reasons to use the Cokin system (or any other square system), 
with dark IR filters it really starts to shine. I doubt any screw 
filter thread, neither lens or filter side, will stand up to the 
continuous screw-on/screw-off exercise. Filter threads are not made 
for such continuous stress and wear pattern, not even a high end 
brand like B+W.
Though one can even go one step further in convenience, and not even 
think about filters during the entire film: a filter behind the 
shutter, between the film rails. For me this was the only way I could 
use a darker filter than #25 with my Sigma 8mm circular fisheye 
(internal screw filters of a very odd/thin size). Regrettably thin 
qualities can only be had in #87C and #87. Would love to add a #89C 
to this collection....
 
> My second question is:  Can I use Cokin red filter nr. 003 for Hie?  Are
> the results reasonable?  

Sure you can. But the darker the filter, the more 'unworldly' the 
effect on HIE will be. Therefore I will soon expand further into the 
darkness with a batch of #87B. By looking at the raw transmission 
data, even #87A should be possible, tripod use provided (as with #87 
and Konica). There is a progressive ^4 power relationship between 
wavelength and the lack of scattering in the air (see another article 
on my homepage), so the additional 100nm or even 200nm should still 
increase the unworldly effect. Perhaps it also shows a different 
IR-reflectance in foliage, who knows....8-))

> Which wavelengths (in Nanometers)  are blocked
> by Cokin 003 red filter?  B+W092 blocks all wavelengths below appr. 695
> Nanometers.

Take a deep breath and dive into the world of spectral transmission 
data on my homepage, including a conversion chart for Wratten, 
Schott, B+W, Heliopan, Hoya and Cokin:
http://www.a1.nl/phomepag/markerink/mainpage.htm

Have fun!....:-))

 

- -- 
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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End of Infrared-Digest V0 #21
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