Kodak HIE and other infrared films

Tim Gray

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Now that spring is coming in full force, I've started shootin my stash of HIE again. Oh, how I wish it was still available. I love the grain, the extended IR sensitivity, the general high speed, and the lack of an anti-halation layer.

So HIE has been unavailable for a while. What have people settled on as a decent replacement? I wonder what the interest would be for a similar product from another manufacturer. Or the feasibility of that ever happening. I'd love it if Ilford came out with a high speed, extended IR film with no anti-halation layer.

A semi related question to PE or someone else. Why does HIE have such a big dip in sensitivity around 520 nm?
 

keithwms

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My guess is that there is an AH dye on some of the current films that could be washed off with buffered water before exposure. Also, you might actually defeat the AH layer by placing a reflective metal behind the film. Been meaning to try both (though I personally don't care halation most of the time, especially when it is supposed to evoke the afterlife in shots from cemeteries. But that's just me).

The films I think you might check out are the new Rollei superpan and the efke IR. I actually like the Rollei IR, which is near IR sensitive, but some won't care for the longish exposures.

The sensitivity dip will just come from the choice of sensitizer, no? My guess is that they swapped out one sensitizer for another... Ron will know for sure.
 

aluk

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Hasn't the efke IR film been (re?)introduced without an anti-halation layer?

Edit: Here it is
 
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Tim Gray

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I should clarify about the dip in sensitivity. Is it there because that's just the way it worked out due to the sensitizer choices, or for other reasons? 520nm is really close to the peak sensitivity in human vision *and* the maximum reflectivity of chlorophyll...
 

Photo Engineer

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Here are the spectral sensitivities of most types of films. What the OP is referring to is seen in the bottom two examples in the attached figure.

IR film can be made to be pancrhomatic and IR sensitive but it is more feasible to make them just blue and IR sensitive as the IR sensitivity is what is being used (or what the customer wants).

Therefore, most IR films have only Blue and IR sensitivity. The exception is EIR which is essentially pancrhomatic and IR sensitive.

It is my understanding that IR dyes become increasingly expensive as they are pushed to longer wavelengths and they become increasingly unstable to heat.

PE
 

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keithwms

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Swapping out the green sensitizer for the IR one(s) would make good sense, since most people who shoot IR are looking to get Wood effect. If the film were sensitive to green reflections and IR reflections then it might be too easy to "blow" the highlights off leaves.

Not sure why they'd want to keep the blue sensitizer though, it seems to me that you give up some sharpness as a result, because the film would then be sensitive to a rather broad spectrum over which most lenses are not apochromatic. Maybe they have no choice, maybe the sensitizers pick up blue as well. A lot of ring compounds absorb in the blue/UV.
 

Photo Engineer

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Keith;

The fundamental sensitivity of a Br/I emulsion is in the UV/Blue region of the spectrum. Unless one uses heavy UV filtration and a lot of Yellow filtration you are going to see the native sensitiityof the emulsion itself. If you Blue sensitize it, you see a rather pronounced bump in the blue sensitivity, usually at about 420 - 440 nm.

PE
 

Photo Engineer

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Keith;

With a blue sensitive only emulsion, in the first row of the figure, it is difficult to say, but in the remaining examples, you see how the sensitizing dye represses blue sensitivity? In those cases, a blue sensitizing dye would have left its trace as a distinct peak in the range I gave. It would show up more clearly. So, in full answer, to #1, IDK, to the rest, most likely no blue sensitizer, just native remaining blue sensitivity.

I'll qualify that by adding that the last row example may have a blue sensitizer. Note the increase in peak?

PE
 
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Ray Rogers

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Photo Engineer said:
...the last row example may have a blue sensitizer.PE
Click to expand...

One thing is curious in that last one...

the sensitivity seems to suddenly cut off somewhat unnaturally (on both ends but esp.) at about 675 or so.

Do you think this is an artifact of some sort ?

Ray
 

Photo Engineer

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Ray;

At least 2 if not 3 monochromators would have to be used for those IR exposures. There would be one more if UV was required. In the manipulation, I'm sure artifacts would apppear. My spectrosensitometer can do that type of exposure, but it must be in 3 stages with a reset and recalibration of the device after each separate exposure.

Picky, picky, picky!

This is the nature of many such spectral devices. In fact, in the far IR case, glass cannot be used in some cases. We used cast Sodium Bromide crystals. They were about 1/2" square, about 1/4" thick and cost more than some people make in a year. They had to be stored in a vacuum dessicator while not in use.

PE
 

keithwms

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Yup that looks like there was a lamp change. To take these data, one would ideally have a lamp with relatively flat output across the wavelength range, but that was basically impossible to get across the whole range from UV to IR. Now you can do it with a really good white light source e.g. a Ti:Sapphire laser pumping a photonic fiber, which they most assuredly did not have when this data was taken. Back then I guess they would have switched lamps, corrected the relative intensities for the lamp spectra as best they could, and just stitched the different wavelength regions together... probably with a copier machine and some tape
 
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