Ever heard of Aerochrome? It’s a unique type of color infrared film, originally created for the US military and designed for surveillance planes. Photos taken with Aerochrome film show trees and other vegetation in vivid reds and pinks, creating images that aren’t quite like anything else.
Sadly, Aerochrome hasn’t been made for over a decade. What’s an enterprising hacker with a fascination for this unobtainable film to do? [Joshua] resolved to recreate it as best he could, and the results look great!
Aerochrome isn’t quite the same as normal film. It is sensitive to infrared, and photos taken with it yield a kind of false color image that presents infrared as red, visible reds as greens, and greens are shown as blue. The result is a vaguely dreamy looking photo like the one you see in the header image, above. Healthy vegetation is vividly highlighted, and everything else? Well, it actually comes out pretty normal-looking, all things considered.
Why does this happen? It’s because healthy, leafy green plants strongly absorb visible light for photosynthesis, while also strongly reflecting near-infrared. This is the same principle behind the normalized difference vegetation index (NDVI), a method used since the 70s to measure live green vegetation, often from satellite imagery.
Aerochrome may be out of production, but black and white infrared film is still available. [Joshua] found that he could re-create the effect of Aerochrome with an adaptation of trichrome photography: the process of taking three identical black and white photos, each using a different color filter. When combined, the three photos (acting as three separate color channels) produce a color image.
To reproduce Aerochrome, [Joshua] takes three monochromatic photos with his infrared film, each with a different color filter chosen to match the spectral sensitivities of the original product. The result is a pretty striking reproduction of Aerochrome!
But this method does have some shortcomings. [Joshua] found it annoying to fiddle with filters between trying to take three identical photos, and the film and filters aren’t really an exact match for the spectral sensitivities of original Aerochrome. He also found it difficult to nail the right exposure; since most light meters are measuring visible light and not infrared, the exposure settings were way off. But the results look pretty authentic, so he’s counting it as a success.
We loved [Joshua]’s DIY wigglecam, and we’re delighted to see the work he put into re-creating an authentic Aerochrome. Fantastic work.
I’ve got some trichrome’d Rollei infrared and Superpan 400 awaiting development, probably with the same filter set!
If digital is your thing, there’s a few good methods as well. Most start with modifying your camera to remove the uv-ir hot mirror filter to make it full-spectrum sensitive. Then you could trichrome like [Joshua] did, or you can use filters to various effect. Kolari makes a filter that emulates the look with a single filter, straight out of the camera, however it doesn’t extend very far into IR, and the true aerochrome buffs don’t think it looks accurate.
The method I’ve been trying recently is documented here: https://hiddenrealms.ch/aerochrome-keep-it-simple/ ([Christoph] runs a fantastic blog, lots of cool image techniques)
It uses a really cool filter that has three light pass-bands, red, green, and NIR: https://midopt.com/filters/tb550660850/
I’ve measured mine, and the transitions are really as sharp as shown in the graph on that page. Optics are so cool, I have no idea how they would make it (Destructive interference except in the passband?)
Here’s a small album of some of what I’ve taken: https://imgur.com/a/gOUiAm8 The burned out forest is interesting, the new/unburned growth shows some great contrast, and (I think) shows why color IR sensitive film was fantastic in surveillance.
All that being said, without doing a trichrome like what [Joshua] does, the IR light leaks into all three channels, as the Bayer filter doesn’t block IR in any color. Anyone have any leads on custom Bayer filters? :D
This is what I am trying to figure out as well. I think you can do this with a two-shot process with the original Bayer filter in place. Shot one would be IR-only, cutting all visible light. The resulting B/W image would be used as the red channel in the final image. Shot two would be an IR and blue cut (not sure what filter or combination of filters to use for this). This second image would have the red channel mapped to the green channel and the green channel mapped to the blue channel for the final image. The issue is that the IR-only shot would be over-represented since it is affecting all pixels on the sensor, while the red is affecting only a quarter and the green affecting only half (assuming a normal RGGB Bayer filter on the sensor).
I presume that if you’re going that route, you would be better served using an R72 filter for your monochrome shot and then a hot mirror filter to block your IR, PLUS an orange filter to cut the blue. But if you’re replacing the blue channel in software you may not even need the blue cut filter.
How about removing the ir filter from you dslrs sensor? Wouldnt that yield similar results (and a camera that can only shoot ir…maybe a lens filter will allow you to take ‘normal’ light photos again?)
I have a DSLR that’s modified how you suggest for astrophotography purposes. While it makes tress look slightly more red, it’s no where near the sensitivity of an actual IR camera, and it doesn’t produce the level of saturation in IR that you see in the photo above.
I want to say “Yes but imagine how complicated that process can be”, but shooting 3 different frames of film is arguably more complicated.
_However_, it’s film – and outside of the whole “I shoot film because it’s just more real maaaaan”-Bubble, there are still normal film enthusiasts who just like using it and looking at it and developing it etc. I’m one of those, I just like having a physical thing with the captured moment permanently etched into it. I also like manual cameras.
So, if one really likes film _and_ one wants to have the Aerochrome look, this method is probably one of the few that can kinda-sorta approximate the real thing.
And let’s be honest. If you like film that much you probably already have some sort of film scanner. And you’re probably actually a little pleased to get fewer pictures out of a roll of film so you can get the thing out of your camera that much sooner.
You could try, but you will still need multiple exposures. When you remove IR cut filter, all three channels become sensitive to IR. As result, you can’t see the difference between ordinary white and dark leafs (dark but with lot of IR, looks white without IR cut filter). You can get same effect with two exposures with two different filters on lens, once with IR cut filter for green and red channels, and once with IR pass filter for IR channel.
Been a long time, but iir you can make a filter out of regular exposed/developed film to block visible light while passing ir.
To clarify for those who aren’t total film nuts: this applies to color film in modern processes. B&W is IR opaque and unexposed Kodachrome may be too.
Yes! This is it. The last issue to resolve then becomes balancing the resulting channels. The sensor will be receptive to IR on all pixels, while only sensitive to red on 1/4 of the pixels and green on 1/2. When remapping the colors this means the end result will be a major overemphasis on the IR to red channel, which is probably ok since most people want that really strong red color, but the remapping of green to blue will overemphasize blue in the final image. There’s probably a simple fix to this but it’s not coming to me immediately.
totally possible and there are even companies that you can send a camera to and they’ll remove the IR filter for you
Noealz does it with just the raw image from a single exposure and some channel balancing (https://mobile.twitter.com/noealz/status/1127057144346361856?s=12), he has some youtube videos on the process, one of them is this: https://youtu.be/i5jllj6A_3w
You totally can. But you also use an extra filter to basically replace the IR/UV filter, and you get really close right out of the camera.
i remember shooting 35mm infrared film in the 70s…my dad bought some rolls to experiment with…same colors as aerochrome…
I wonder how images would looks if a camera could somehow use the red channel for infrared, green for visible, and blue for uv.
kolari vision makes a chrome filter for modded DSLRs https://kolarivision.com/product/kolari-vision-ir-chrome-lens-filter/
I use this setup quite a bit. It works really well
I thought I remembered hearing of a chemical process you could use to “hyper” normal film, astrophotographers used to use it. Which if used with hella stopped down lens in daylight would look similar. Maybe you needed additional filters, wasn’t up on all the details.
I’m not sure it’s even technically chemical so much as structural but one of the most common techniques is to soak the film in hydrogen gas before exposure.
Why not just use lomochrome purple….
There are RGB-IR sensors that substitute half of the normally green pixels with IR pixels. With that would just require a bit of image processing and you get this effect without any filters.