IE yellow/oranges (was: IR- screw Leica rangefinder option? Don'

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

On 27 Aug 96 at 17:45, Robert Long wrote:

> On Tue, 27 Aug 1996 09:55:51 +0100, you wrote:
> 
> |I guess Joe ment that since darkloading is near impossible, EI is 
> |the only sane alternative.
> 
> IR Ektachrome can be loaded in subdued light, instead of total
> darkness, then?  I had forgotten.

Yep, just like ordinary film. 
Btw, it just occurs to me that this fact is sortof proof for my 
HIE argument that both IR-leaking felt trap *and* the lacking 
antihalation layer are responsible for the fogging of HIE. The felt 
trap of IE should leak as much as HIE, and yet it doesn't fog.
 
> |Btw 1: you can use opaque IR filters with EI, but you end up with an 
> |overall red image; red in those parts where HIE would be bright white 
> |when using the same filter.
> 
> That's what I meant by losing the full color spectrum of the film.  I
> don't see any point in it.

It *could* be interesting if there would be completely IR-absorbing 
elements in the picture....like bright red plants against a black 
soil. Must do some experiments some time....
 
> |Btw 2: the recommended minus-blue *is* an ordinary yellow filter,
> |Kodak recommends #12, but I wasted an entire film with it; I have
> |used a b&w orange #21 from Cokin, and was very satisfied with
> |results. Inbetween there is also a color #16. 
> 
> First, according to Kodak's spectrographs, a No. 12 has an extremely
> sharp cutoff at 500 nm, whereas the other yellow filters (8,
> medium-yellow, K2; 9, deep-yellow, K3) are less sharp and include some
> shorter wavelengths.  When I've tried these filters or orange (Wratten
> 21?), I've consistently found the color to be similar but not as clear
> and clean and vibrant.  I therefore stopped using anything but a
> Wratten 12 with the material. 

Yep, you are right about the steep cut off compared to #8 and #9.
But even besides that, both #8 and #9 are roughly 20nm more 
transmissive towards the blue, it's not just the steepness of the plot.
Another interesting difference, at least according to my 1928
Wratten catalogue: #12 also shows a 2-3% transmissive 'dip',
centering around 310nm. Not much, but apart from #15, none of the
other yellow/orange colors shows this dip.


> I don't understand how you could have
> "wasted an entire film with one."  But I haven't used the material in
> at least ten years, so maybe it has changed?  Not likely.

Oops, I screwed up in my numbers: the Cokin yellow I used was a #8 
yellow for b&w. And this one is recommended by Kodak....
Anyway, I ended up with a horrible blue cast. Perhaps I shot at the wrong
time of day, and in too harsh light (Spain, mid summer), and maybe
even overheated the film....but the #21shots under the same