One-Image Aerochrome with Green and Orange filter

[Stefano]

I don't know why people are so squeamish about subtracting channels or so set on getting things straight-out-of-camera. I always edit all my images anyhow, what's one more step? And you can always make a photoshop action or whatever.

I have some thoughts about this. Having a quicker result may be handy and useful in some situations. Or maybe another reason is that people may feel manipulating a photo too much makes it less "authentic" and "natural", but this doesn't make sense considering how we take photos here. Even a WB is a manipulation, and in our case (for UV and IR photos) it is very strong. The mere act of seeing invisible light makes our photos "unnatural" in my opinion.

 

But another good reason is videos. I don't think there are many softwares (if any) that allow you to do the kind of post-processing you did here on videos.

[dabateman]

I don't know why people are so squeamish about subtracting channels or so set on getting things straight-out-of-camera. I always edit all my images anyhow, what's one more step? And you can always make a photoshop action or whatever.

 

I haven't found time to fully label and sort my photos, let alone properly edit them in one of the tens of photos editing software I have.

I have recently thought to just nail everything in the camera. Then its done, as I compose with the framing and color I want.

This was part of the push to get a Pen-f camera. Its amazing at color and monochrome in camera with curve adjustment

live while viewing. But its only stock not full spectrum. I did get my Em5mk2 converted to full spectrum though.

[Andy Perrin]

But another good reason is videos. I don't think there are many softwares (if any) that allow you to do the kind of post-processing you did here on videos.

Honestly, that would be trivial in MATLAB, and I've actually done similar things. I can't recall if I ever posted my thermal time-lapse to the board, but I made a time lapse over several hours showing the vanishing of text from an advertisement as the sun set. That was done with MATLAB. Channel switching and so forth would be equally easy. I should post an example.

 

dabateman, I never take more photos than I plan to edit the next day or two. Not letting them build up is key for me.

[Andy Perrin]

I'll take a stab at that. Foliage in red is dark due to chlorophyll absorbing out to about 720 nm. Throw in an IR signal and the same leaves go quite pale. Some dark blue surfaces will behave similarly.

Since my answer was that I expected the saturation to decrease in areas of high IR reflectance, I think we agree?

[Stefano]

I can't recall if I ever posted my thermal time-lapse to the board, but I made a time lapse over several hours showing the vanishing of text from an advertisement as the sun set.

You didn't post videos, but you posted about the fading sign: https://www.ultravioletphotography.com/content/index.php/topic/3935-fading-signs-in-lwir

 

I would be interested in channel-swapping some UV-IR videos I made. Blue skies and red tones.

[Christoph]

Green only if LED (no IR.) Yellow if incandescent, and red plastic lenses also go yellow.

 

Pulling this off without subtraction looks difficult to me.

 

Taillights are yellow, red berries are yellow as well. This color change occurs with Orange-Green...

 

 

[Andy Perrin]

The sky color looks off to me, but if you are happy with it, that is all that matters.

[Christoph]

I'm not 100% happy with it, Andy. Otherwise I would not post anymore. But I would not have criticized the color of the sky Too blue for you?

[Stefano]

To verify the accuracy, you could try a rainbow or a diffraction grating and see if it looks normal.

[Christoph]

Unfortunately I don't have the tools (or the rainbow) ... But a simple color checker could also help... or just comparing shots of Orange-Green with Two-image-IRG....

[Andy Perrin]

Saturation hue looks off to me somehow, not like a blue sky in visible light (and not just because it’s darker, which we expect in IR) but most people here know I’m somewhat colorblind with red/greens so you should probably ask someone else! So maybe it’s fine, but I think I’m out of this conversation. Once it gets down to judging tiny color differences like this, I can tell you what I think but it may not match your own vision.

 

I tend to be good with technical details and I can tell you something like what the effect of not doing the subtraction will be on the image but I can’t tell you how it looks to the eye fo someone who isn’t me.

[Stefano]

As a non-colorblind person (tested), watching this on an AMOLED/OLED screen (I don't know the exact type, but it's not LCD), the sky looks about right, but a bit greyish, not well saturated. Increasing saturation a bit may fix it.

 

*just checked, it's an AMOLED display.

 

Also, just saw Andy's edit. We agree on the blue sky. Andy, your vision might not be that far off in some circumstances.

[Andy Perrin]

Stefano, I know it isn’t, but the problem is that I am awful at predicting when it’s misbehaving.

[dabateman]

A garden hose is a good controllable rainbow source.

[Christoph]

Unfortunately, I've reached my photo upload limit here. I was outside earlier and took some photos to see how well the orange and green filter method reproduces the “Aerochrome-specific” color changes: one set with the Orange-Green combo, the other with the two-photo technique. In my blog I have posted the corresponding photos as well as the steps necessary in Photoshop. So if you are interested: https://hiddenrealms.ch/blog/

[Andy Perrin]

Yeah, you should replace your earlier too-big photos with properly resized ones and then you'd have space. Andrea wrote up the preferred photo dimensions and compression settings here:

https://www.ultravioletphotography.com/content/index.php/topic/1321-publishing-guidelines-upload-file-size-and-pixel-dimensions/

[Andrea B.]

Unfortunately, I've reached my photo upload limit here.

 

Christoph, I'm going to go move you to the Members+ group so that you can upload again.

 

Done!

[Christoph]

Thanks, Andrea!

[Christoph]

I had only a few seconds of sun today, during the last days it has been raining and snowing almost continuously here. I could use the short time window to test the orange-green filter method with video. I had always failed before because I wanted to set white balance and color tones exactly the same as for photos in Photoshop.

 

The problem with video is, first, that you don’t get the same result with white balance in post as you do with photos. I assume this is partly because you can’t film in a RAW format (at least with my camera), and simply the detection of neutral tones works differently in Premiere with video. Also, you can’t move the hues around like you can in Photoshop. Accordingly, attempts to swap the channels (you can do that in Premiere) or with the channel mixer were doomed to failure.

 

I therefore tried it differently and finally succeeded. I did the following:

I set the white balance in the camera to 2500 Kelvin (with no changes in tint). Then I selected the standard variant in the color presets and reduced all sliders there by 1-2 strokes, so that contrast and saturation were reduced.

When filming, I made sure (and this is very important) that the image was underexposed.

Once in the box, I imported the video into Premiere and made a few changes to the channel mixer (under Color Correction). I entered the following values there:

 

Red:

70

0

200

 

Green:

150

0

-100

 

Blue:

70

70

-100

 

That’s all. Here’s the result. There’s still room for improvement, but I really like it so far:

 

https://vimeo.com/506751984

[Andy Perrin]

Pretty!

 

In terms of getting the original colors in RAW, one way to do that would be to put a 850nm+ long pass filter on the camera first, and white balance in-camera. Because the Bayer filter is transparent at 850+, that should give you the "unwhitebalanced" colors. Then you could do the channel mixing and subtraction. I'm not sure how that would compare to what you got above, but it might be interesting to try.

[Stefano]

Andy, that's a clever idea. It isn't a true RAW but if one isn't too picky on the exact colors it should work.

[Christoph]

Will try that, Andy! Thanks!

[Cadmium]

Hmm, Doing a movie like that is cool!

[Christoph]

https://vimeo.com/509835258

 

https://vimeo.com/509835178

 

Channel mixer only (in Premiere), slightly different values than above. Neutral setting in-camera, underexposed shot.

[Cadmium]

Christoph, Excellent! Bravo!