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Red foliage with UV-IR cut filter + BG-3 filter

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#1 Hornblende

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Posted 16 March 2017 - 00:24

Hi all,
I was playing with my filters and I tried to stack some filters to see what happens. Well, I stacked the Lifepixel UV-IR cut filter with the Lifepixel Super Blue Infrared filter (wich is very similar to Schott's BG-3) and my plants foliage turned red!
I think this is interesting because it kind of reproduce by itself the look of IR film pictures.

I used an incandescent light source and the WB was done on the PTFE piece.

Canon 6D full spectrum - Carl Zeiss Jena Tessar 50mm f/2.8 - ISO 800 - f/2.8 - 0.3"
Attached Image: IMG_8578 - copie.jpg

Edited by Andrea B., 04 June 2017 - 20:42.


#2 Hornblende

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Posted 16 March 2017 - 01:18

I tried to replicate this effect in photoshop by taking a normal visible image and replacing the green channel by the blue channel (RBB) The result is similar but the red color is not so bright and way less saturated.

RBB image
Attached Image: IMG_8581.jpg

Image with BG3 + UV-IR cut filter stack (the PTFE piece is overexposed).
Attached Image: IMG_8582 - copie.jpg

Edited by Hornblende, 16 March 2017 - 01:42.


#3 Andy Perrin

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Posted 16 March 2017 - 02:03

Goodness, now I would love to see what will happen when we have some warm weather and the leaves come out!

#4 Hornblende

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Posted 16 March 2017 - 02:09

Same!
We are having a huge snow storm here on the east coast, I wonder if spring will ever come.

Edited by Hornblende, 16 March 2017 - 02:09.


#5 Cadmium

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Posted 16 March 2017 - 21:03

Hornblende, Quite beautiful and interesting, but...
Based on the graphs you linked to, the UV-IR cut graph appears to match with BG40 2mm.
My experience with BG3 + BG40 produced cerulean (turquoise blue) foliage, not red. So your results are much different than what I would expect from BG3 + BG40 or even BG38 stacks.
Anyone who has BG3 and BG40/BG38 might want to try that stack, and see if you get red or turquoise foliage.
Attached Image: UVIRcut_BG_L.jpg
Attached Image: BG3_2mm_BG40_2mm_stack.jpg

#6 Andy Perrin

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Posted 16 March 2017 - 21:27

Hm. The plant may be very dark between 300-500, but due to Wood's effect, very bright in the near IR where that "leak" is? So if all the NIR ended up in the red channel after WB, maybe that makes it red? Here is a vegetation spectrum. Also, incandescent light might be heavy on the IR.

http://physicsopenla.../30/ndvi-index/
Attached Image: veg.jpg

Edited by Andy Perrin, 16 March 2017 - 21:31.


#7 Hornblende

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Posted 17 March 2017 - 00:23

Quote

Also, incandescent light might be heavy on the IR

Now I want to know what happens under sunlight. If it is indeed turquoise it is not very fun.

#8 Andrea B.

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Posted 17 March 2017 - 00:32

Camera: Nikon D610 conversion
Lens: Coastal Optics 60/4.0
Filter Stack: BG3 + Baader UV/IR-Cut
Subject: Matthiola incana and some leaves on a Spectralon target

ADDED LATER --> This photo was made in mixed lighting. Also the TV and laptops were all on. Too much blue??


With this stack, the recording is predominately in the blue channel.

Here is the raw composite from Raw Digger.
Attached Image: 610_0068rawComp.jpg

Here is the white balanced version. Colour profiling has not been applied.
Attached Image: 610_0068wbNoProf.jpg
Andrea G. Blum
Often found hanging out with flowers & bees.

#9 Andrea B.

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Posted 17 March 2017 - 00:37

......and I have a question.
Why does Life Pixel call that filter a UV/IR-Cut??
It clearly is not cutting UV. Strange!
Lifepixel UV-IR cut filter
Andrea G. Blum
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#10 Hornblende

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Posted 17 March 2017 - 01:04

Adrea : Yes, I was wondering the same thing..

Your picture is interesting, wat king of lighting did you use? What happen if you use an incandescent light?

#11 Andy Perrin

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Posted 17 March 2017 - 01:21

Hornblende, don't you have that pocket spectroscope? Can you visualize the spectrum of your light source for us?

#12 Hornblende

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Posted 17 March 2017 - 01:38

My light source is a tungsten filament light bulb, which emits this kind of spectrum:
Attached Image: Emission-spectrum-of-incandescent-bulb - copie.jpg


- The tiny red/IR leak of the filter stack + high reflectivity of the plant is sufficient to overwhelm the red channel.
- The green channel does not record much signal since green light is filtered out.
- The blue channel does not record much signal because very little blue light is emited by the lamp

In the end, red foliage under incandescent light makes sense.

Edited by Hornblende, 17 March 2017 - 01:41.


#13 Andrea B.

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Posted 17 March 2017 - 05:07

Martin, let me retry with only an incandescent bulb with all other lights turned off. And the TV and laptops turned off also!! I'll be right back with some results.

I added in my post above about the lighting. I think the TV might have been the problem. The guys were watching the basketball games.
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#14 Cadmium

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Posted 17 March 2017 - 06:03

Andrea, your not going to get it with your Baader UV/IR-Cut filter. Pull out your Schott BG38.

#15 Andrea B.

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Posted 17 March 2017 - 06:09

Camera: Nikon D610 conversion
Lens: Coastal Optics 60/4.0
Subject: Color Checker Passport and Spectralon
Lighting: Incandescent Bulb with no other ambient light
Filters: BG3 with Baader UV/IR-Cut, BG40, BG39, BG38 and S8612
All filters were 2mm thick, so each stack was 4mm.

The results depend very much on which IR-blocker is used. The raw composite versions show that the blue channel is predominant for all filters. However, the BG38 also has a strong red channel so that the the BG38 raw composite is almost magenta. The white balanced versions show strong red only with the Baader UV/IR-Cut and the BG40.

These photos are about 400 pixels wide. They should appear in side-by-side pairs if your browser is expanded enough. The left photo is the white balanced version. The raw composite is on the right. The white balance is not perfect for two reasons: (1) I have not yet made colour profiles for the converted D610. (2) When there is a strongly predominant channel, you sometimes see imperfect WB in bright areas.

EDIT: Fri 17 March 2017
I replaced the original images with a set which is free of cat fur.
Thank you converters which supply a clone tool.

BG3 + Baader UV/IR-Cut
Attached Image: BG3-2_BaadUvirCut_20170317wf_207pnWB.jpgAttached Image: BG3-2_BaadUvirCut_20170317wf_207rawComppn.jpg


BG3 + BG40
Attached Image: BG3-2_BG40-2_20170317wf_212pnWB.jpgAttached Image: BG3-2_BG40-2_20170317wf_212rawComppn.jpg


BG3 + BG39
Attached Image: BG3-2_BG39-2_20170317wf_219pnWB.jpgAttached Image: BG3-2_BG39-2_20170317wf_219rawComppn.jpg


BG3 + BG38
Attached Image: BG3-2_BG38-2_20170317wf_230pnWB.jpgAttached Image: BG3-2_BG38-2_20170317wf_230rawComppn.jpg


BG3 + S8612
Attached Image: BG3-2_S8612-2_20170317wf_234pnWB.jpgAttached Image: BG3-2_S8612-2_20170317wf_234rawComppn.jpg
Andrea G. Blum
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#16 Cadmium

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Posted 17 March 2017 - 06:35

Well, I was wrong about UV/IR-Cut.
Here are my tests using an incandescent bulb:
Left: Visual (Baader UV/IR-Cut), Center: BG3 2mm + Baader UV/IR-Cut, Right: BG3 2mm + BG38 2mm.
Attached Image: Vis_BG3_x_BUVIRc_BG38_1080.jpg

#17 Andrea B.

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Posted 17 March 2017 - 06:51

I really like the oranges showing up in the white balanced BG3 + BG38. Some interesting art possibilities there perhaps.

The Baad UVIR-Cut did not behave well in my stack. Looks somewhat washed out. Probably the shiny surface caused some flare, methinks.
Andrea G. Blum
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#18 Cadmium

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Posted 17 March 2017 - 07:49

I tried the BG40, which is the target BG filter, which is closets on the overlay of the LifePixel graph.
I didn't think it looked good, but I will redo that. It should look half way between the Baader UV/IR-Cut and BG38 colors.
The LifePixell graph is a BG type filter, probably BG40.
Your BG40 color look closer to my BG38 colors. But we probably are not white balancing the same, mine was just full frame Marque, seemed to look best to me on all of them.
Your UV/IR-Cut looks kind of fogged with orange, so I am wondering it that is the best white balance for that one?

Edited by Cadmium, 17 March 2017 - 07:50.


#19 Andrea B.

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Posted 17 March 2017 - 14:42

Traditionally, white balance is made on some subject which is neutral in colour. That would be a subject with RGB values like (X,X,X), all the same. Although you don't want to use too dark of a neutral subject. Use white, near white or very light gray subjects for WB.

So I use white balance sampling, droppers or marquees only on the 99% reflective, diffuse Spectralon because average white balance across an entire frame may create colour casts on neutral subjects.

Color casts happen anyway. Sometimes it takes two trips through the converter to get white looking like white. First on the raw, then on the resulting tif.

No, the Baader UVIR-Cut does not play well in this particular stack under that particular lighting. The fogging is probably flare (as mentioned) due to the shiny Buvircut surfaces.

****

Argh!!! I just saw cat fur on the Spectralon!!! Winter is IMPOSSIBLE. Too much static electricity indoors. Argh, argh argh.
Andrea G. Blum
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#20 Cadmium

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Posted 17 March 2017 - 16:26

Andrea, try white balancing on the cat fur, you know WhiBal makes that new target now, WhiPur.
(that was a joke, meow).
Well I white balance on all sorts of things to find what is best. But forget about that,
here are two new tests.
The first is shot indoors with BG3 2mm + BG40 2mm, but I think the main difference here is that I shot this with my 18-55mm VR kit lens, which has poor UV transmission, and seems to make it more red that way than on the Kuri.
I need to compared those directly, I might be wrong on that, but I got nothing like that with the Kuri when stacking the BG40, and as I said, I am pretty sure what Hornblende has is a BG40.
White balance was full frame.
The second shot was shot outdoors, it is raining, and this was a BG2 2mm + BG38 2mm stack, with the 18-55mm VR.
White balance was the sky and upper dark trees, not the grass.
You may not get the same white balance using Ninja, I am using CNX2 for these.
Also, I have a feeling these are going to white balance a LOT differently with various light and sun, this outdoor pic below looks pretty cool to me, but I am not going to hold my breath for it to look that good when the sun is out, which might seem opposite of what one would expect, but... just a feeling.
Another single filter you may want to try for outdoors, is the Hoya B-410, Colon kinda discovered that, and he has some good examples of how red that can look, which I personally have never been able to duplicate, mine come out looking more orange.

Hornblende, I would really like to see you go take a snapshot outside, if there is anything green out there at all.

BG3 2mm + BG40 2mm, 18-55mm VR lens, incandescent light:
Attached Image: BG3_2mm_BG40_INCAN_600.jpg

BG3 2mm + BG38 2mm, 18-55mm VR lens (this is the stack that was so orange with the incandescent lighting):
Attached Image: BG3_2mm_BG38_2mm_1020.jpg

Edited by Cadmium, 17 March 2017 - 16:30.