How to avoid having yellow tones when shooting color infrared

fabulousrice said:

I shot the first one a while back

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fabulousrice said:

I had a few rolls of color infrared film sold by Film Photography Project.
I shot the first one a while back, and a lot of the photos had yellow tones like this

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fabulousrice said:

I had a few rolls of color infrared film sold by Film Photography Project.
I shot the first one a while back, and a lot of the photos had yellow tones like this one:

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And some photos produced a better result like this:

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I don't remember if one of them was cross-processed and the other one processed normally.
How can I make sure that my results look like the image on the bottom, rather than the top image while shooting and having the film processed?

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BAC1967 said:

I shot these with Kodak Aerochrome Infrared film using a yellow filter and never got yellow like that. Did you use a different filter or no filter? Infrared film is best with bright sunlight from behind you, could you have been facing in the direction of the sun? Cloudy day?

High Desert Farm House by Bryan Chernick, on Flickr

This one has clouds making the sky white but I still had bright sun from behind me.

Cape Creek Bridge by Bryan Chernick, on Flickr

More examples here: Aerochrome

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neilt3 said:

According to the information provided in your link you should be using a wrattan #12 yellow filter on your lens.
That would explain the yellow caste .
The second picture looks like it had no filter .
It's a very expensive film , if it's there's you bought !
Especially out of date film .

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fabulousrice said:

The second picture looks like it had no filter? What do you mean? Would the tree look red if there was no filter on the camera?

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reddesert said:

As I understand color infrared film, keeping in mind I haven't used it, it produces false-color images where the dye color is sensitive to light one step redward of the color it produces. So for example in a normal film you have layers sensitive to blue/green/red light that produce respectively blue/green/red colors in the slide. While in color IR you have layers sensitive to green/red/infrared light that produce respectively blue/green/red colors in the slide.

You use a yellow filter to cut out the blue light that would contaminate the three false-color channels. But unlike B&W infrared, using a red filter doesn't give you a "more infraredish" look. It cuts out the green light, so you only get the red and IR channels, which make green and red colors in the slide, not blue. So the red filter makes an image that looks like it was taken through a yellow filter.

neilt3's explanation of the yellow filter causing a yellow cast would be okay for true-color film, but this isn't true-color. Just use the yellow filter that the film is supposed to be used with.

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fabulousrice said:

I think you misunderstand how color infrared film works.

Color infrared is sensitive to different light wavelengths. It doesn't shift colors the way you would do it in photoshop.
For example you could take a picture of extremely dark, almost black foliage and it would look red. There is no way to select only black foliage in a photograph and "shift" the color otherwise everything that has shadows or dark areas would be shifted too.

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reddesert said:

No, I do understand how color infrared film works, but you are correct that it can't be trivially duplicated by altering a true-color image in photoshop. Color IR film creates a false color image because each of the three layers of the film is sensitive to a redder color of light than the dye that it makes. Green light makes blue dye, red light makes green dye, near-IR light makes red dye. The yellow filter is used to eliminate blue light, presumably because some of the layers are also sensitive to blue light.

Vegetation reflects strongly in the near-IR; this is why it appears white in B&W infrared images with a red or 720nm filter passing only red and near-IR light (the "Wood effect"). Using color infrared film, that near-IR light is rendered as red dye, so vegetation comes out red.

Using a red filter on color infrared film will just screw things up. It will eliminate the blue light and the green light, so you get no blue dye, so your images have a yellow cast.

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reddesert said:

Vegetation reflects strongly in the near-IR; this is why it appears white in B&W infrared images with a red or 720nm filter passing only red and near-IR light (the "Wood effect").

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fabulousrice said:

I still think we have a different understanding of how it works.
Vegetation is NOT green in 60% of instances and yet it comes out as red.
I have taken lots of infrared pictures of yellow, black, blue, purple, etc plants and they come out looking red

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reddesert said:

It does not matter much whether the vegetation is green or blue or purple in visible light. What matters is that it reflects a lot of near-infrared light (or fluoresces to emit near-IR light as JensH pointed out). If it is very bright in the near-IR, it will expose the near-IR-sensitive layer of the film, that layer will get converted to a so-called cyan dye, transmitting red light in the transparency.

A couple of useful resources are the Aerochrome datasheet at https://125px.com/docs/unsorted/kodak/EN_ti2562.pdf and this page: https://www.analog.cafe/r/kodak-aerochrome-a-colour-ir-film-guide-and-review-uwi3 Fig 1 from the datasheet shows a sort of flow chart of how different wavelengths of light expose different layers of the film and the resulting colors. It also explains the use of the yellow filter.

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Figure 2 shows the spectral sensitivity of the different color layers. We can see that the layers are all very sensitive to blue, which is why the yellow filter is needed. However, a red filter would also cut off the layer labeled "Yellow (G)" [yellow dye sensitive to green light], which forms the blue areas when reversal processed.

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fabulousrice said:

Thank you so much for this insightful answer. So to make sure I understand correctly, if I want to have results that look like the picture of the palm tree, I should use a yellow filter and process it in C 41 chemistry, correct?

I wonder if someone has made comparisons of what the results would look like depending on what filters and what type of processing is used.

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