my best aerochrome simulation yet

[Fandyus]

I have spent countless hours lately reprocessing all my images taken with an orange filter on a full spectrum camera. I spent a lot of my time over the last year or so researching all the ways one could emulate aerochrome, but none really satisfied me. This method though, I think, can look very faithful. It is done almost entirely in Darktable (with the use of one simple LUT to switch the color channels). There are several aspects to this process. One important aspect is that I switch the input color profile to "linear Rec709" which disables the default color channel subtraction cameras use today to mimic lifelike colors. I find that this gives the images a more filmlike appearance (because films don't do this). Then I do the normal color swap you would do for digital aerochrome, red channel for blue channel, and then blue channel for green channel. Lastly, I use the color contrast setting and I set the blue yellow contrast to 5. This gives the image the sort of color depth that you would get with real IR-R-G images. I find that it actually does all sort of things that you'd expect from real aerochrome, for example, red LEDs render as green, green LEDs render as blue. There's subtle differences to the shade of red foliage takes on depending on what species it is, human skin also gets the weird yellow-beige tone that you'd get with real aerochrome.

I used Jason Kummerfeldt's aerochrome images for reference. Namely, images from this video.

 

Here's an image that is not great overall but it displays what this method is capable of very well. (please note that the "Autodrom" sign was made of red lights, most likely LEDs)

 

Next up are two images that show how the skin tones look.

 

Other images are a random selection.

comparison shot on my phone:

 

[Chris Barne]

Interesting! 

 

I may have to try some of this processing out. I was just thinking about writing a post about my own aerochrome efforts, but I haven't thought it through fully yet.

 

An orange filter is much more light than I get with my current set up! You have no infrared reduction from a filter at all in this set up?

[Fandyus]

@Chris Barneno infrared reduction. Orange filter only is how aerochrome was commonly shot back in the day, I do realize that modern cmos sensors are are sensitive a bit further into IR but it doesn't seem to be enough to have an effect.

[lonesome_dave]

Great stuff Fandyus. I used the #21 orange filter quite a bit with color IR film back in the day and it usually resulted in greenish skies and red-orange vegetation. The only way I ever got blue skies was with the #8 light yellow or #12 deep yellow filter. The latter one is what Kodak recommended. 

The color renditions you show here are what I would expect with a yellow filter in front of color IR film with a fair amount of boosting of chroma and contrast in post.

It looks good to me even though my taste is for a little less chroma. I like the church one best.

[colinbm]

Beautiful, I like them all.

[Fedia]

Great Fandy ! I'll share some of my latest images later. I'm impressed by your linear rec709 hack. The separation beetween green light and infrared light is very articulated. It doesn't seem that infrared ligh is influencing the green and red channels, which is surprising without any Ir reducing filter.

 

 

[Fedia]

10 hours ago, Chris Barne said:

An orange filter is much more light than I get with my current set up! You have no infrared reduction from a filter at all in this set up?

Same for me ! May I ask what your filter setup is ?

[Chris Barne]

13 minutes ago, Fedia said:

Same for me ! May I ask what your filter setup is ?

Of course! I use the triple bandpass 550/660/850 from midopt on the back of the lens and a Hoya X1 on the front as a red and IR cut. 

 

I'm drafting a thread of my workflow, but I'm currently on mobile so I think I'll have to wait until this evening when I have access to my PC.

 

I've been a lurker for some time and I've seen and actually tried out your filter stack, but I found that I would get blown out skies due to the foreground being so dark.

[Fedia]

On 4/26/2024 at 10:39 AM, Chris Barne said:

I've been a lurker for some time and I've seen and actually tried out your filter stack, but I found that I would get blown out skies due to the foreground being so dark

I didn't encouter this problem. What camera and lens are you using ?

 

There is a big drawback in using the TB. It acts essentially as a mirror for all the light it doesn't pass. The result is the light gets trapped between the filter and the lens (if you use it in front of the lens) or between the filter and the sensor (if you use it behind the lens). It can be hard to deal whith grey skies as it tends to bleed all over the image. It is best to use the filter behind the lens. When I used the filter in front of the lens I had an inverted "ghost" of the scene that wandered around the frame as I pointed the camera. The pink gel adds even more reflections...

 

Yet it is the only method that allows you to bypass the color substraction stage as it is designed to pass a lot of red compared to IR to make sure the red channel records red light primarily and not IR light.

 

Fandy's method of using a traditional orange filter is the best to get good contrast and dynamic range. You just have to work on the colors more.

[Chris Barne]

I use a Nikon d5200 and the Nikkor 28-80, the combo takes good monochromatic infrared photos so my assumption was that it would also work for aerochrome. TB is attached to the back and anything else on the stack is at the front. The other benefit of the FX lens onto his camera body is that I don't need to worry about vignetting from filter stacks. 

 

I replied to your other thread where I mentioned that I have been using a Cokin pink filter so maybe I'll try and get a Lee filter in and see if that works any better. 

 

Wish I still had free and easy access to spectrometer...

[Unscenerie]

I'm very intrigued to emulate your process, Fandyus.

I can't figure it out, though. Could you help me out?

 

I shot with an orange filter (no brand; gives an IR look).

In Darktable for the input color profile I chose linear Rec709 RGB (you didn't mention the RGB in the name but there's no other). (Working profile is also linear Rec709 RGB on default.)

Then I do the color swap (color calibration in Darktable): see attached screenshot

Then color contrast: blue yellow contrast to 5

 

No matter what I try, or what color swapping pairs I try out, I never achieve your look. Maybe my orange filter isn't suitable for this? Screenshot attached.

Thanks for advice.