False color IR with Harman Phoenix?

[Yobo57]

I noticed Harman Phoenix 200 has extended red sensitivity past 700nm and a relatively high peak at around the 665-685 range.

Theoretically, with about a 680nm filter or something like a ZWB3 filter, would it be possible to take false color infrared photos with this film stock? Maybe even 720nm and long exposure times?
The scans would definitely need to be white balanced afterwords.

I know the graphs is for tungsten, not sure how much this affects the values for daylight or if it’s negligible.

What do you think, is it worth a shot to try?

 

[Andrew O'Neill]

Oooooh! I'm very much intrigued!

 

[dcy]

What do you think, is it worth a shot to try?

Please, do try it. What do you have to lose? You could sacrifice 1/3 of a 35mm roll and take 12 shots at +1 stop increments. With 12 stops of range, you'd have a pretty decent chance at either finding an exposure that works, or proving that it doesn't work. Pick a scene that's likely to look good in IR (lots of trees, sunny day, sun behind you).

Do you already have a filter?

 

[koraks]

Theoretically, with about a 680nm filter or something like a ZWB3 filter, would it be possible to take false color infrared photos with this film stock?

No. What you could do is use a 680nm filter and obtain a totally red image, but it won't be anything resembling a false color 'IR' photograph. The red exposure will only create cyan dye, so there will only be one color in the final image. It will not be much different than any other color film (negative or positive) shot through a deep red filter.

For false color IR you need wavelength shifting; so longer wavelength captured light needs to be converted into a color that corresponds to a different wavelength in the spectrum. That's what e.g. Kodak HIE did. Basically, it would capture IR and show it as red, capture red and show it as green etc. That's a bit of a simplistic way to put it, but it's the basic principle of how the stuff worked. It relies on the fact that the sensitizing dye (which determines the layer's spectral sensitivity) and the dye coupler (which controls the color of the dye generated during processing) are distinct aspects of the emulsion and can be chosen in separation from each other. Harman Phoenix is no different from any other regular color negative film in this regard.

 

[khh]

What you could probably do is shoot it like a trichrome exposure, but with each exposure on the same frame, and substitute the red filter for a 680nm or higher filter to capture more infrared than ordinary red. It still wouldn't look like aerochrome, though. Unless I'm completely messing up the color model in my head, it should shift folliage towards a more yellow hue.

 

[koraks]

Unless I'm completely messing up the color model in my head, it should shift folliage towards a more yellow hue.

If you shoot through a red filter, what part of the film is going to create yellow or magenta dye? Or do you mean a regular exposure without filter followed by one through a deep red filter? Even so, you'd just be creating additional cyan dye (=red in the positive photo). It would just shift the color balance of the entire frame towards red.

 

[dcy]

If you shoot through a red filter, what part of the film is going to create yellow or magenta dye? Or do you mean a regular exposure without filter followed by one through a deep red filter?

Given the reference to trichrome, I think a strict reading of @khh's suggestion is to take three photos with three filters: blue, green, and IR.

I had a similar idea, but @khh's is more interesting. --- My idea was to have blue, green, red, and IR filters and then do digital post-processing to shift the wavelengths. But then I said to myself "What's the point? You can do that with plain IR-sensitive B&W film".

@khh's idea, if I understood it correctly, doesn't require digitally shifting colors. It just deletes red and replaces it with IR.

 

[khh]

Given the reference to trichrome, I think a strict reading of @khh's suggestion is to take three photos with three filters: blue, green, and IR.

I had a similar idea, but @khh's is more interesting. --- My idea was to have blue, green, red, and IR filters and then do digital post-processing to shift the wavelengths. But then I said to myself "What's the point? You can do that with plain IR-sensitive B&W film".

@khh's idea, if I understood it correctly, doesn't require digitally shifting colors. It just deletes red and replaces it with IR.

Yes, exactly. Three exposures of the same frame using a blue filter, a green bandpass filter and an IR filter. You could get the same effect with two exposures using a lowpass filter and a highpass (i.e. IR) filter, but it would probably be even harder to color balance that correctly.

Edit: I mean, as I said you wouldn't end up with aerochrome looking stuff, and what you got probably wouldn't look very good. But it should be a true IR color image.