Re: Fiddling with odd filters for EIR

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

On 11 Aug 97 at 15:13, JoePaduano@xxxxxxx wrote:

> Willem, I've used a Cokin green fiter with the new EIR film and the results
> are not very different from using a deep yellow filter. The vegetation is a
> stronger magenta color though and the sky remains blue, but clouds become a
> light magenta instead of recording white. When using a filter that only
> allows transmission of infrared, all objects basically look magenta with very
> little contrast.( not cool looking at all)

Note though that the range of greens I mentioned where all strange 
types of green, not ordinary b&w green (Wratten #13)
Normal greens show a 100% transmission somewhere between 500 and 
600nm, the ones I mentioned are 50% at most, some even less than 10%. 
Combine this with blocking red (#13 only blocks red partially), and
100% transmission of IR, and the (visual) tonal balance of the film
should be equal, but with red replaced with infrared, hence more
distinction in foliage (theory), or at least a different infrared
tonal range. But to pronounce the IR, you must gradually block the 
range from 500-600nm, otherwise the IR spectrum 800-900nm will be too 
weak to be recorded.

I don't expect any sensible prediction of the three layers in EIR,
but it should be different than #13 green. The problem is that there
are dozens of green types (never occurred to me before!), the best
approach seems to pick one of the greens that starts at 480nm and
start fine tuning with no extra filter, then #8, #12 and #16.

You really need the transmission plots to visualize what 
is roughly required....:-))


- -- 
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'!]
*
****
*******
******************************************************
*  To remove yourself from this list, send:          *
*         UNSUBSCRIBE INFRARED                       *
*       to                                           *
*         MAJORDOMO@xxxxx                            *
*----------------------------------------------------*
*   For the IR-FAQ, IR-Gallery and heaps of links:   *
*  http://www.a1.nl/phomepag/markerink/mainpage.htm  *
******************************************************

------------------------------