Jump to content
UltravioletPhotography

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


Hornblende

Recommended Posts

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"

post-136-0-06925500-1489622960.jpg

Link to comment

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

post-136-0-70135500-1489626974.jpg

 

Image with BG3 + UV-IR cut filter stack (the PTFE piece is overexposed).

post-136-0-32921400-1489626975.jpg

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

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.

post-87-0-44769400-1489698117.jpg

post-87-0-87443500-1489698102.jpg

Link to comment
Andy Perrin

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/

post-94-0-27912600-1489699641.jpg

Link to comment
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.

Link to comment

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.

610_0068rawComp.jpg

 

Here is the white balanced version. Colour profiling has not been applied.

610_0068wbNoProf.jpg

Link to comment

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?

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

My light source is a tungsten filament light bulb, which emits this kind of spectrum:

post-136-0-18468200-1489714220.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.

Link to comment

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.

Link to comment

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

BG3-2_BaadUvirCut_20170317wf_207pnWB.jpgBG3-2_BaadUvirCut_20170317wf_207rawComppn.jpg

 

 

BG3 + BG40

BG3-2_BG40-2_20170317wf_212pnWB.jpgBG3-2_BG40-2_20170317wf_212rawComppn.jpg

 

 

BG3 + BG39

BG3-2_BG39-2_20170317wf_219pnWB.jpgBG3-2_BG39-2_20170317wf_219rawComppn.jpg

 

 

BG3 + BG38

BG3-2_BG38-2_20170317wf_230pnWB.jpgBG3-2_BG38-2_20170317wf_230rawComppn.jpg

 

 

BG3 + S8612

BG3-2_S8612-2_20170317wf_234pnWB.jpgBG3-2_S8612-2_20170317wf_234rawComppn.jpg

Link to comment

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.

post-87-0-47066900-1489732500.jpg

Link to comment

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.

Link to comment

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?

Link to comment

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.

Link to comment

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:

post-87-0-07866000-1489767746.jpg

 

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

post-87-0-17657800-1489767757.jpg

Link to comment

....you know WhiBal makes that new target now, WhiPur.

 

I absolutely MUST get that!! :lol: :rolleyes:

 

*****

 

The reason we try to always white balance on a good reflective target is so that comparisons can be made across various platforms and converters.

 

With accurate white balance and colour profiles, the effects of different illumination or different lenses can be better judged.

Link to comment

I have generally find the best results with full frame Marquee. I really miss it with other cameras.

However, there are other time it looks best white balanced other places.

The reason I WhiPur'ed the outdoor pic on the sky/top of dark trees is because the sky was a little yellow when using full frame marquee, with an annoying white edge to the tree line,

and I wanted it to look more natural.

Try it out outdoors if you want, and see what you come up with.

Link to comment

White balance is a matter of taste in artistic photos. But even with the reduced false colour range when shooting UV, white balance accuracy is better when the WB is made on something UV-white or UV-light grey rather than averaging over an entire frame. Here is one example. The differences are real, but subtle between spot WB on a white Spectralon target versus average WB over the whole frame. How much these differences matter depends on what one is trying to illustrate.

 

In this example, I don't think I can detect the differences just by eyeballing it. But that's an observation for this example. Other examples may show more striking differences.

 

[The journey from the original raw NEFs to the reduced size, sRGB JPGs shown here may have introduced further colour bias which is impossible to control.]

 

 

White balance was made on the white target in Capture NX2 using the Marquee tool. The sample RGB values were made in PSE using a 5-px dropper in the middle of the white and grey targets as determined by a selection bounding box.

d600Stds_uvBaadSB14_uvNikkor_040513wf_5275spotWB.jpg

 

An average white balance was made on the entire frame in Capture NX2 using the Marquee tool. The sample RGB values were made in PSE using a 5-px dropper in the middle of the white and grey targets as determined by a selection bounding box.

With average white balance the white target has a very slight green bias.

The grey target is deficient in blue.

d600Stds_uvBaadSB14_uvNikkor_040513wf_5275aveWB.jpg

Link to comment

Well try it with a green leaf in there, might be interesting.

As far as my pics, the incandescent ones can also be white balanced on the white square, which looks about the same as the full frame marquee with these.

I didn't use any target for these other than what you see in the pics.

Enjoy ;-)

 

Below for reference, either full screen or arrow got me the same result.

 

Vis, BG3 + UV/IR-Cut, BG3 +BG38 (all three with Kuri 35mm lens), incandescent bulb:

post-87-0-62395300-1489774570.jpg

 

BG3 + BG40 (with 18-55mm VR lens), incandescent bulb:

post-87-0-00064600-1489774582.jpg

Link to comment

I have nothing green to shot at, but here is an outdoor picture.

 

Lifepixel super blue + UV/IR-cut, Canon 6D, Carl Zeiss Jena Tessart 50mm f/2.8

White balance on the snow.

post-136-0-18729900-1489775199.jpg

Link to comment

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
×
×
  • Create New...