Re: Filter equivalent test

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

On 15 Jun 98 at 11:50, Timothy E. Coffer wrote:

> Date:          Mon, 15 Jun 1998 11:50:09 -0400
> From:          "Timothy E. Coffer" <COFFER.TIM@xxxxxxxxxxx>
> To:            infrared@xxxxx
> Subject:       Filter equivalent test
> Reply-to:      infrared@xxxxx

> I just purchased a B&W #090 filter. I noticed right on the box that the
> Wratten equivalent for this filter is a #24 light red, as opposed to a #25 as
> listed in most catalogues. For those of you that are really picky about
> your filter cut offs, etc., keep this in mind. 
 
According to my 1925 Wratten Light filter catalog, #24 is called 
'Projection Red' (whatever that might be).
Never looked at the 'reds' carefully, but there is an staggering 
number of those (take a seat please):

23 E (Red)
23a E Red (light)
23b 2-Color Red
24 Projection Red
24a Projection Red (light)
25 A (Tricolor Red) 
[note WJ: seems as if "25A" has a totally different meaning than 23a 
or 89B....the latter being part of the Wratten system itself, the 
first more a translation of '25']
26 Stereo Red
27 Stage Red
27a Stage Red (light)
28 Cine Red
29 F

Fascinating book....you won't find the same hairsplitting
differences in the current Wratten catalog....and it has that lovely
old smell as well....:-))



 

- -- 
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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