"Anti"-trichromes

As I imagine most people on this forum would know, a trichrome is when you use a red, green, and blue filter to expose three frames of black and white panchromatic film, which you can then combine together to create a colour image.

But what about antitrichromes? From the moment I found out about trichromes I wondered if the opposite was possible—three B&W images on single frame of colour film using filters—but wasn't able to really find anything online... I mean, I don't even know what to search for, if this concept has a name I wouldn't know how to find it.

But in principle it seems you could expose a single colour frame three times with different images filtered with R/G/B and then scan and extract each channel in photoshop to have separate B&W images. I imagine that given imperfections in various things here (the filters, the chemicals, the scanning setup, etc.), what you'd end up with is a muddy/messy result where channels bleed into each other a bit... but I bet it would look interesting. The orange mask might be a problem... maybe on Aero 100 cross processed in E6?

You mean “anti” as in shooting through cyan, magenta and yellow filters (instead of RGB)?

I would risk saying that you could get these in Photoshop and use them as channels in a CMYK image. Heck, you could even shoot a frame without any filters and use it as the K channel.

It’s either that, or my brain is not working good

fdonadio said:

You mean “anti” as in shooting through cyan, magenta and yellow filters (instead of RGB)?

I would risk saying that you could get these in Photoshop and use them as channels in a CMYK image. Heck, you could even shoot a frame without any filters and use it as the K channel.

It’s either that, or my brain is not working good

Click to expand...

Noo I meant shooting three different images onto a single frame and extracting them out.

Mockup I made in Photoshop:


From which you can extract three B&W images:

illawarraflametree said:

But in principle it seems you could expose a single colour frame three times with different images filtered with R/G/B and then scan and extract each channel in photoshop to have separate B&W images. I imagine that given imperfections in various things here (the filters, the chemicals, the scanning setup, etc.), what you'd end up with is a muddy/messy result where channels bleed into each other a bit... but I bet it would look interesting. The orange mask might be a problem... maybe on Aero 100 cross processed in E6?

Click to expand...

Your reasoning is sound as far as I can tell. Yes, there will be crosstalk between the images for the reasons you mention. And yes, it'll look interesting! The orange mask is not really a problem if you scan the film. Give it a try!

Attic Darkroom gave it a try @3:14:


He calls it "reverse trichrome" and the conclusion is that is sometimes works but most of the time it doesn't.

illawarraflametree said:

Noo I meant shooting three different images onto a single frame and extracting them out.

Click to expand...

Oh! Now I get it and the “channels bleeding into the others” makes total sense now.

I don’t think there’s a way to get the images separated without this extra info.

It sure a crazy way to save on film, three shots per frame!

OAPOli said:

He calls it "reverse trichrome" and the conclusion is that is sometimes works but most of the time it doesn't.

Click to expand...

The problem is most likely due to the fact that this approach is very sensitive to crosstalk in several stages of the imaging chain. In the video, he does address the inherent crossover between the layers and the issue of imperfect filters. What he skips or maybe doesn't realize is that there's also crosstalk during digitization. The latter could be minimized by using selective wavelength illumination while digitizing the film. With today's technology, this is within reach of consumers, but will involve a little electronics DIY. The crosstalk during exposure is more tricky to handle; it would involve highly selective and effective band-pass filtration for green and blue and a sufficiently long-wave filter for red. Apart from the difficulty in acquiring/setting this up, the evident drawback will be that the spectral sensitivity of the process will be very specific and different for each photo. This will have a huge effect on how a scene renders.

Yeah, I would love to see if this can get better results by minimising crosstalk during exposing and scanning with good filters and the right wavelength narrowband LEDs during scanning.