Tiffen 85B good choice for EIR?

[Athiril]

I got a remaining roll of EIR in the fridge I never shot.

Was wondering if a genuine Tiffen 85B which I have would make a good filter for it as opposed to straight yellow?

 

[nworth]

The 85B is a light balancing filter to convert daylight to 3200K. It still lets a lot of blue light in, which makes for strange, blue results on IR film. A No. 12 (minus blue) filter is the usual recommendation. A No. 15 will probably work (with somewhat orange results) and so would a No. 8 (with somewhat blue results).

 

[Athiril]

No. 12 is ideal? I'll save the film then, until I get an ideal filter. Thought it may be a good filter (the 85B) since it's orange in colour.

 

[thisismyname09]

I've used some aerochrome, which is iirc essentially the same thing as EIR, with the #12 filter. The results are quite good. It essentially blocks out all blue light and allows from green to IR through. Since all of EIR's layers are blue-sensitive, you'd somewhat fog the film if you let blue light reach it.

I have an extra #12 3x3 inch gel... Though with my experience with shipping to/from australia, it would probably be cheaper to see if you can find one locally even if I offered it just for the price of shipping.

 

[2F/2F]

The 85B is a light balancing filter to convert daylight to 3200K. It still lets a lot of blue light in, which makes for strange, blue results on IR film. A No. 12 (minus blue) filter is the usual recommendation. A No. 15 will probably work (with somewhat orange results) and so would a No. 8 (with somewhat blue results).

What he said.

Color IR film is a "false color" film, meaning that the spectral sensitization of each layer does not necessarily have anything to do with the color of dye used for that layer. In a regular film, if an emulsion was sensitized to green light, a dye is used that will give you green in the end; a false color film would use a different dye to give you a color other than green in the end. What you see is not what you get; this is by design.

As such, it will not respond to color or to filters as one would think. Also, it is heavily blue without filtration, so the no. 12 gets rid of this. It is your baseline filter to "normalize" the film (if anything about this film can be called "normal").

A look at the cross section of the film in the data sheet will show you why the #12 is the filter for which the film is designed, and give you somewhat of an idea of what to expect and perhaps give you some ideas for manipulation of the images.

 

[2F/2F]

P.S. I found the data sheet on my computer.

This might help:

You have the normal dye layers that any transparency film has: cyan, magenta and yellow.

Here is the part to wrap your head around. :

All three layers are sensitized to blue light plus one other color of light.
Cyan dye layer, which gives you red in the end, is also sensitized to IR.
Magenta dye layer, which gives you green in the end, is also sensitized to red light
Yellow dye layer, which gives you blue in the end, is also sensitized to green light

Thus, these are the following "paths" of the types of light at the scene of the shot to the final transparency:

Blue light never makes it past the No. 12 filter => no layer is exposed by blue light => final image gives you black for blue

Green light passes through filter and exposes green-sensitive layer => green-sensitive layer produces yellow dye => final image gives you blue for green

Red light passes through filter and exposes red-sensitive layer => red-sensitive layer produces magenta dye => final image gives you green for red

IR passes through filter and exposes IR-sensitive layer => IR-sensitive layer produces cyan dye => final image gives you red for IR

So, you end up with the same final three layers in the transparency as you get on any other E-6 film, but none of them have been rendered by their own color of light.

Again, red becomes green, green becomes blue, blue becomes black, and IR becomes red

 

[Athiril]

Yeah I understand how it works. Sine an 85B reduces blue light for more blue sensitive films (tungsten films) to shoot in more blue sources (daylight) figured it may be good.

But cheers, I'll wait till I get my hands on a No. 12 filter, I'd like it to be spot on