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First attempt at IRG

Infrared Processing
17 replies to this topic

#1 Stefano

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Posted 18 November 2020 - 21:11

Today I tried to "shoot" (more to "generate") an IRG image. I took the visible light image with a piece of chinese BG39 (2 mm) on the lens, the IR image with a Hoya R72, processed the visible image to have the original green channel on the blue channel and the original red channel on the green channel (getting rid of the original blue channel), converted the IR image to B&W and then to red, and stacked the two images. The result is OK color-wise, but the images are clearly not aligned, and it's not that great in general. As a concept, I like it.

Attached Image: somma 256.jpg

Tell me if this is the right section for this kind of work (maybe the ultraviolet and multispectral was better) and also if I need to write the settings of the original images.

#2 Andy Perrin

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Posted 18 November 2020 - 23:55

I think I've been putting them in this section also? We tend to regard a lot of the infrared/visible mix photos as "infrared" and this is also true more generally online I've seen.

Photoshop improved the alignment a lot at the expense of losing some edges. I think you could do the same in Hugin also.
Attached Image: Stefano IRG.jpg

Edited by Andy Perrin, 19 November 2020 - 00:31.


#3 Stefano

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Posted 19 November 2020 - 05:22

Thanks Andy, that's much better.

#4 dabateman

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Posted 19 November 2020 - 05:55

I think this post has the method or command line code for Hugin to do the alignment for you. This was posted by Bernard:
https://www.ultravio...__fromsearch__1

#5 Cadmium

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Posted 19 November 2020 - 06:01

Naw, you don't need Hugin for this, not if you have Photoshop, it has an alignment feature.
Two photos, visual and IR. Stack them, then use Photoshop Edit, Auto-Align Layers.
Visual photo: move green channel to blue, move red channel to green, desaturate IR shot, move to red channel of visual shot. Auto balance.
Nice job, Andy.

Edited by Cadmium, 19 November 2020 - 06:03.


#6 Andy Perrin

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Posted 19 November 2020 - 06:53

View PostCadmium, on 19 November 2020 - 06:01, said:

Naw, you don't need Hugin for this, not if you have Photoshop, it has an alignment feature.
Two photos, visual and IR. Stack them, then use Photoshop Edit, Auto-Align Layers.
Visual photo: move green channel to blue, move red channel to green, desaturate IR shot, move to red channel of visual shot. Auto balance.
Nice job, Andy.
Thanks -- I suggested Hugin because it's free, and I don't think Stefano has access to Photoshop. (I used Photoshop when I did it.)

#7 Stefano

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Posted 19 November 2020 - 07:41

Currently, I don't have either programs. Reading what Bernard wrote about his processing technique (linked by David), you also have the issue of different magnifications, since the focal length of the lens is not constant for all wavelengths. It doesn't seem to be a big issue for me, but maybe I will need to solve it too.

#8 Andy Perrin

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Posted 19 November 2020 - 09:03

I have never had significant trouble with magnifications. The alignment algorithm (in any software) will handle small differences for you.

#9 Stefano

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Posted 19 November 2020 - 09:05

I tried again. My camera has trouble focusing in visible light, apparently. This time I used a tripod.

Visible:
Attached Image: P1000548 - Copia.JPG

IR:
Attached Image: P1000549 - Copia.JPG

IRG:
Attached Image: somma 257 - Copia.jpg

To convert the visible light image to R->G and G->B I use IrfanView, I do a channel swap (RGB->GBR, the last option) and then remove the red channel. Is this correct?

#10 OlDoinyo

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Posted 19 November 2020 - 14:58

You have the right idea, but you might want to de-veil your IR frame before using it. The glare is adversely affecting your tonality.

#11 Stefano

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Posted 19 November 2020 - 23:33

What do you mean with "de-veiling"? I too noticed the IR frame appears "bubbly", maybe I need to shoot it changing the strong white balance I use to take the visible image. Is that the issue?

#12 Andy Perrin

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Posted 19 November 2020 - 23:42

The IR is a bit overexposed, Stefano.

#13 Stefano

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Posted 19 November 2020 - 23:59

Ok. I will try again tomorrow lowering the exposure time.

#14 dabateman

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Posted 20 November 2020 - 00:59

Your last IRG looks like an old 1970's film shot.
Your IR doesn't look blown. You could just open it in your favorite editor and drop the EV by -1 or -2. RawTherapee might work for that as a free option.


#15 Stefano

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Posted 20 November 2020 - 01:02

It didn't look overexposed when converted to B&W, but the channels suffered a bit due to the strong blue color of my chinese BG39, which makes IR appear very red. It actually looks almost normal in B&W.

#16 Stefano

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Posted 20 November 2020 - 13:46

Ok, I'm back. This time I reduced the exposure of the infrared image, and did a quick in-camera white balance in order to avoid blowing the channels. I also put a paper tissue to white balance the resulting image.

Visible:
Attached Image: P1000579 - Copia.JPG

Infrared:
Attached Image: P1000580 - Copia.JPG

IRG stack:
Attached Image: somma 258 - Copia.jpg

White balance on the paper tissue in IrfanView:
Attached Image: primo WB - Copia.jpg

White balance on the concrete in Irfanview:
Attached Image: secondo WB - Copia.jpg

...it didn't work as I expected. Too much red when white balanced on the paper.

#17 Andy Perrin

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Posted 20 November 2020 - 23:10

White balance on the paper did work in PhotoNinja for me. Very similar to your concrete results:
Attached Image: post-284-0-43171300-1605879694.JPG

I think this may mean that you need to do a white balance on a region (average white balance) which you can do in PN by dragging around on the neutral object.

Edited by Andy Perrin, 20 November 2020 - 23:14.


#18 Stefano

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Posted 21 November 2020 - 00:25

Thanks Andy. It seems IrfanView struggles a bit at white balancing, it may not be the best software to do it. The image you obtained looks so natural and balanced (no pun intended), the colors are very nice.