IR - can it be made into colour?

[Overread20]

Ok musing thoughts here late at night/early in the morning. Simply put is it possible to take a photo in IR (film/digital) and then adjust it to present the photo as a normal colour exposure? I know they can take old B&W film and turn it into colour via a tinting method - but what about IR and the digital world?

 

[480sparky45 44]

You could probably do it, at least make a color image out of it. But it wouldn't represent anything, at least I don't think it will.

In other words, it will not represent a 'color shift' from a wavelength in IR to a wavelength in the visible spectrum.

You might be able to do it using the same technique astrophotographers utizile: Taking luminance, red, green and blue photos using red, green and blue filters. Then combine them into a color image. But you would not be able to use red, green and blue filters.... you would need filters designed to allow only specific wavelengths in the IR.

 

[Garbz]

What is your goal? IR is a thin band of wavelengths and most IR photos are represented as black and white as they are one channel only. The false colour film IR photos are actually only partially IR with a shift in wavelength as a result of developing. Typically they do things like use a yellow filter to cut out blue and the reversal process then renders IR light red, green light blue and blue light grey.

Digital it wouldn't be directly possible without using a filter to select the wavelengths as desired as sparky said, because there is no process where colour is added to a chemically sensitive film. If you shoot a picture with a modified IR camera and a yellow picture you'll end up with a yellow picture and no amount of white balance will get those colours to shift.

So what are yo trying to achieve?

 

[dupek]

Playing with RGB will get you some colors.

 

[Overread20]

It's part of my longer term plan to build an IR nighttime photography setup - a cheap rebel camera with liveview (and video) modified for IR combined with a few IR spotlights (for lighting) - thus giving my a setup that can do nighttime photography without disturbing anything (mostly, since of course different creatures see different parts of the light spectrum).

Being able to modify the results into real colour would be a major boon in this - however considering the subjects I'd not expect to be able to take a series of several shots which could later be stacked together.

 

[Garbz]

Not really possible. If you illuminate the sensor with only IR you will reflect only IR. This is a single small band. Your best bet for colour would be to manually paint the subjects afterwards using a colour layer in photoshop (quite possible and quite pleasing if you do it right given how texture will be handled by the greyscale layer).

However it's not possible to get the true colour because the true colour of what you're looking at is a narrow band of infrared. If you took a photo of me as I sit here right now you'd have a guy typing at a laptop with a green and blue stripped jumper with grey coloured cuffs. If you were to take a photo of me with your setup with only IR and no colour light passing back you'd get a guy typing at a laptop with a white jumper with white cuffs.

Many things in the visible band look completely different in IR. Inks on cloths, coloured leaves, lipstick, even my cat loses it's orange stripes (but not it's black) when taken in IR. This colour can only be recorded in colour, so your only option left is to fake it.

 

[Overread20]

Ahh the point about colours is indeed interesting - esp how its affects fur colouring.

Also I got reminded by another on another site that IR can also be affected by the heat/temperature of a subject and that two identically coloured and surfaced subjects when at different temperatures would show differences in the IR light amount they give off.

 

[Garbz]

Depends on the sensitivity of the IR. Thermography works in the mid-IR band, we're in the near-IR band. I haven't seen it mentioned specifically in terms of IR photography but I think it could be conceivable that some gets picked up by IR cameras.