infrared editing in creative cloud

[davidhaney0404]

Now that I can finally afford Photoshop and Lightroom I am wanting to swap the red and blue channels in my IR files but can't find anything up to date on how to this with the current photoshop. Any thoughts, how tos, or ideas? Thanks

[D Fosse]

IR is a moving target. What are you trying to do, specifically?

Generally, you use a channel mixer adjustment layer. It's pretty self-explaining when you open it, just set one input to 0% and the other to 100%.

Since you ask about channel swapping, the standard procedure for "IR false color" is to take two exposures, one IR filtered and one normal. Then you shift all the channels one step sideways, leaving a slot for the IR data in the original red channel. The original blue channel is discarded. I don't know if this is relevant for you, so I'm not going into the details now.

[Chuck Uebele]

Forgot about channel mixer, that works well.

[Chuck Uebele]

If you want to swap them, I would create new alpha channels and save the original channels there, so you can write over one, then retrieve it from the copy to paste or apply to the other original channel.

[D Fosse]

I'd just like to add that with digital sensors, IR is monochrome, grayscale data. There's no meaningful separation between the red, green and blue-sensitive pixels. Normally IR is effectively filtered out, so you'd also need a camera with this filtering removed from the sensor.

This is why you combine separate IR and visual exposures into what is known as IR false color.

IR film is a different matter.

[davescm]

Hi

You could just add a channel mixer adjustment layer and set the Red output to come from 100% blue and the Blur to come from 100% Red

So this :

Plus this :

gives

Dave

[davescm]

Looks like the others replied whilst I was taking screenshots

Dave

[Jeff Arola]

All kinds of stuff here about infrared and photoshop.

https://www.lifepixel.com/photo-tutorials/infrared-photoshop-basics

[D Fosse]

When shooting infrared with a modified camera, it's important to know what's really happening.

The red/green/blue Bayer filter array on the sensor is intended for visual light. When you move into IR, the Bayer array behaves very differently. Some of the IR passes through the red filter, a little less through the green filter - but most of it passes through the blue filter.

At the same time, the IR band beyond red is still very narrow, even with the IR cut-off filter removed from the sensor. Once the offset between red/green/blue has been corrected, you're left with perfectly monochrome data, a grayscale image.

The point being - the IR information is not meaningfully separated from the visual information. Instead it contaminates the visual information. It's all mixed up.

The only way to truly separate them, is to use a very steep IR-pass filter in front of the lens, cutting off all visual light. This is very difficult to work with since you can't see anything. There's also the IR focus shift to compensate for - this is what the red focus point, the additional red dot, on most lenses is for.

And there's one more complication: Ultraviolet. When removing the filter pack from the sensor, the camera extends not only into infrared, but also ultraviolet. Again, there's no way to separate these two components without additional cut-off filtering in front of the lens. They both pass mainly through the blue filtering in the Bayer array.

What I'm getting at, is that the link above presents a somewhat inaccurate and simplistic picture. IR isn't necessarily what you think it is. These people modify cameras, so it's in their interest to present it as easy and fun. Fun it can be, in that you get unexpected colors, but it may not be very accurate or even reproducible.

[davidhaney0404]

Heres the original photo from my modified pentax istD

[davidhaney0404]

Here is after channel swapping and lightroom

[davidhaney0404]

The pic doesn't look like that on my monitor unfortunately

[D Fosse]

The first thing you need to do is "normalize" the channels so that they have roughly equal output and dynamic range. Here you have some channels severely underexposed and this is why you get the heavy color cast.

Use Levels for this, and set the black and white endpoints for each channel separately, so that the three channels roughly overlap in the histogram. Here's your original first, and then with red and blue swapped:

Note, again, that there's no "correct" way to do this - unless you follow a standardized procedure such as what I outlined above. There's no visual reference for how it "should" look.

BTW I did this in Photoshop since you posted jpegs, but normalizing the three channels is best done in Lightroom in the raw stage. Just get a good balance between the three channels. "White balance" is not really a meaningful concept here, but that's what you're doing, only on a purely subjective and visual basis.