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Fall Leaves in full spectrum

Infrared
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#1 GaryR

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Posted 24 October 2020 - 01:03

Not much time for photography lately, but managed to grab some backyard shots before all the leaves disappear. All taken with the Sigma sdQ-H w/Sigma 70mm DG macro + KG3

Attached Image: _SDI1299.jpg

Attached Image: _SDI1301.jpg

Attached Image: _SDI1305.jpg

Attached Image: _SDI1306.jpg

#2 colinbm

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Posted 24 October 2020 - 02:17

Good on you Gary
The KG3 reduces the IR a bit ?

#3 Cadmium

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Posted 24 October 2020 - 06:34

Gary, Great colors, very nice photos! :smile:

#4 GaryR

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Posted 24 October 2020 - 14:55

View Postcolinbm, on 24 October 2020 - 02:17, said:

The KG3 reduces the IR a bit ?

Actually, I got the idea for using the KG3 on the sdQ from Steve.
In FS mode, the sdQ produces way too much red in the IR range. The KG3 attenuates the excess red, and there's plenty of IR to work with.
https://www.newport....ew-502954110916

#5 GaryR

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Posted 24 October 2020 - 15:01

Thanks Steve!
Getting ready for a major move to another town, so this is a last look in our current back yard.

#6 Andy Perrin

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Posted 24 October 2020 - 16:21

Love this!

#7 ultrainfra

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Posted 27 October 2020 - 00:23

Nice pictures!

What do the leaves look like in visible spectrum only? It was my impression that leaves reflect IR due to chloryphyll so I'd have guessed in full spectrum the autumn leaves look as if a red-enhancer filter was used on a normal camera (which is kinda what those pics look like!). Leaves haven't changed here yet so I can't find out for myself just yet.

#8 Stefano

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Posted 27 October 2020 - 00:43

View Postultrainfra, on 27 October 2020 - 00:23, said:

It was my impression that leaves reflect IR due to chloryphyll
...yes and no. It is actually a good question. Chlorophyll doesn't absorb IR, as IR light is both reflected and transmitted by leaves, but I don't know for sure why foliage is white in IR. Doing some research on Internet I found that this brightness is in a small part due to UV/VIS induced IR fluorescence, but for the most part it should be due to light scattered in the spongy mesophyll layer.

#9 Andy Perrin

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Posted 27 October 2020 - 01:09

Yeah, I think scattering is responsible for the Wood effect (named for Robert Wood, not the plants).

#10 Cadmium

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Posted 27 October 2020 - 01:13

Myself, I am going to just go for the simple explanation that the IR is reflected by the chlorophyll.
Certainly you can induce IR fluorescence, either with visual or UV, however, that requires fairly long exposures in total darkness void of all other light (visual and IR).
Such weak fluorescence does nothing more than does visual fluorescence in daylight photos.
Keep in mind these are not IR photos, these are full spectrum photos with attenuated IR, but my point being is that what you see here is a mixture of the full spectrum.
Furthermore, I have the same leaves on the ground here, outside my door, I just now walked out there and looked at them, and there is a mix, some are entirely brown, no green, no chlorophyll,
and others have some chlorophyll left, mixed in with the dead parts, and even a few look almost entirely green still.
If you ask me, IR reflected from the chlorophyll, everything else doesn't really figure in to the results here, except the visual colors.
Also, there are examples above that show still alive leaves, and completely dead leaves, the pumpkin with the dead leaves, and the still alive pumpkin vine (?) for example, all of which follow what I am saying.

Edited by Cadmium, 27 October 2020 - 01:18.


#11 Andy Perrin

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Posted 27 October 2020 - 01:46

It's not a thing that's subject to opinion, this is a known fact that it is scattering, not chlorophyll (which is mostly transparent in IR), which is responsible for the Wood Effect, Cadmium.

Attached Image: Screen Shot 2020-10-26 at 9.45.49 PM.png

https://www.osapubli...seq=0&mobile=no

Edited by Andy Perrin, 27 October 2020 - 01:48.


#12 ultrainfra

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Posted 27 October 2020 - 05:11

View PostAndy Perrin, on 27 October 2020 - 01:46, said:

It's not a thing that's subject to opinion, this is a known fact that it is scattering, not chlorophyll (which is mostly transparent in IR), which is responsible for the Wood Effect, Cadmium.

Attachment Screen Shot 2020-10-26 at 9.45.49 PM.png

https://www.osapubli...seq=0&mobile=no

I think I may have been slightly misunderstood. I knew (or believed) the IR 'Wood effect' comes from the reflection of chlorphyll, but since autumn leaves have much less of the compound I was curious if what he saw visibly looked much different than the full spectrum shots posted.

Still that's some neat information, thanks for sharing! From my understanding of it, they are saying that chlorphyll does indeed reflect IR and does not absorb it (as is commonly thought), but rather than being the cause of the wood effect, it simply enables it by virtue of not absorbing NIR. But perhaps my interpretation is incorrect.

I wonder why if it is the case chlorophyll isn't directly responsible the wood effect that dead vegetation tends to look much darker than live vegetation. When the leaves start changing here perhaps I can take some photos of vegetation I previously photographed in IR and/or full spectrum and post a comparison! But I don't mean to derail the thread so I'll stop my musings here!

Edited by ultrainfra, 27 October 2020 - 05:15.


#13 Andy Perrin

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Posted 27 October 2020 - 06:07

Ultra, I was responding to Cadmium in my last post, not you (or at least not you directly).

In fall, other things change about the leaves than the chlorophyll. There is a lot going on here. Definitely dead vegetation looks different than living vegetation. But stuff like water content also matters to scattering so if that changes than it may explain some of the difference.

Edited by Andy Perrin, 27 October 2020 - 06:11.