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Rhytisma acerinum, on Maple

Multispectral
3 replies to this topic

#1 Mark

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Posted 02 November 2017 - 23:09

Someone told me recently there was "a big problem" with "the trees suffering from disease this year". And then this maple leaf was picked up and presented to me, as if it offered incontrovertible evidentiary truth. It seemed plausible - and worth spending some time under my lens.

Shown here in VIS, the leaf itself was unremarkable in form, though the large black 'disease spot' was prominent and surely indicated a terrible affliction.
Attached Image: 10-09-2017_20-02-20_baader-whiteLED.jpg

Looking at it under UV, discerning features practically disappear into an even-toned stone-like appearance.
Attached Image: 10-09-2017_19-57-33_andreau.jpg

Still under UV, but looking at the UVIVF now, a striking fluorescence is revealed. After a bit of internet'ing I now know this to be Rhytisma acerinum, a fungus commonly found on maples which does not normally cause substantial harm to the tree. How about that - the internet is good for more than just watching cat/dog videos after all ;)
Attached Image: 10-09-2017_20-00-13_baader-mte.jpg

Moving on in my multispectral set to the IR image revealed another surprise. Here the hysterothecia (fruiting bodies) are now visible within the stroma (thank you again, interwebs).
Attached Image: 10-09-2017_20-04-41_r72.jpg

While I often include an extended IR (filtered to ~1K nm cut-on) image in my multispectral sets, it is almost just as often that I am rather unimpressed with the typically boring (aesthetically) results. But not this time - here the hysterothecia are a bit more obvious with the slight increase in contrast.
Attached Image: 10-09-2017_20-10-36_eo1k.jpg

And to close the set I shot a UVIIF image. Here, the chlorophyll containing areas IR-fluoresce as expected, while the extent of damage in other areas is obvious.
Attached Image: 10-09-2017_20-05-35_r72-uviif-1xmte.jpg

Shooting info:
Camera
- Nikon D750 [broadband] + 50 mm Nikon Series E lens + 12 mm extension tube
Lens filters
- UV: AndreaU-MKII
- VIS & UVIVF: KV418 + 420 nm LP + Baader UV-IR cut [stack]
- IR & UVIIF: Hoya Y(K2) + R72 [stack]

- Extended IR: Xnite830 + 1K nm longpass [stack]
Illumination/Irradiation
- VIS: White LED bulb
- UV & UVIVF: 4 x 18" T8BL-B + FL-02 glass
- UVIIF: MTE-U303 + Hoya U340
- IR: 40 W incandescent clear glass bulb
Exposures

- 1/20-20 s
- ISO320
- f11


#2 Andrea B.

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Posted 02 November 2017 - 23:41

Very interesting. Nice side trip into the fungi world. Our UV/IR/FL photography is so very revealing, isn't it? B)

BTW, something fun to try with autumn leaves: Find at least 3 and pose them in an overlapping manner. Then shoot in IR to reveal the IR-translucency of the leaves. The outline of the underlying leaf portions are revealed thru the top leaves. Q.v.
Andrea G. Blum
Often found hanging out with flowers & bees.

#3 Andy Perrin

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Posted 03 November 2017 - 04:08

The colors in the UVIIF are my favorites. It's interesting that there seem to be several different areas. There is the visible-black area, and then some of the lighter parts (in visible) which show up in the other photos. And of course the fruits which are not apparent in the visible pic.

#4 JCDowdy

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Posted 07 November 2017 - 17:00

Very good, you should consider publishing this, perhaps as a short technical note in a relevant journal.