UV reflective vs UV reactive(=fluorescent)

Discussion in 'Fly Tying' started by jwg, Feb 7, 2013.

  1. jwg

    jwg Active Member

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    I came across a good article about the difference between materials that reflect UV, which we cannot see, and those that absorb UV and then fluoresce at wavelengths we can see.

    Of most interest to me, it discusses which fly natural fly tying materials are likely to be UV reflective.

    These include peacock herl.

    "(the Royal Coachman has white feathers (highly UV
    reflective) and peacock herl (blue/green—next highest UV reflective"

    Jay
     

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  2. Norm Frechette

    Norm Frechette Googlemeister

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  3. jwg

    jwg Active Member

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  4. Alchemist

    Alchemist Soaking Wet

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    From everything I have read, the UV-salmonid connection is very weak, which makes intuitive sense. The attenuation length of UV light in any natural water is considerably shorter than visible wavelengths, making it a poor candidate for general underwater imaging. That is not to say specific uses might be made by certain fish, but most of the UV craze is pretty pictures and mumbo jumbo. UV-induced fluorescent materials are a slightly different story. But if anyone thinks the actual underwater effect in fishing situation is anything like what is observed in a darkened room with a UV lamp... well I have some magic UV-beans for sale in the classifieds.
     
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  5. jimmydub

    jimmydub Active Member

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    Like Alchemist said above, I'm not so sure there's much to the UV concepts with trout fishing. It seems that most animals with UV vision are night feeders or deep dwellers, and usually there's a tradeoff between UV vision and visual acuity. While it would make sense that salmon and larger trout (those that feed at night) would have a need for better UV vision, I think the highly developed lateral lines in these fishes make up for their loss of sight to darkness. These fish have terrific visual acuity, and probably detect just enough light outside the visual spectrum (on each end) to get by in low light situations.

    In all the applications of night fishing for monster browns, I have not yet heard of someone skating a gigantic Royal Coachman. I have, however, heard of large leech patterns, large dragonfly nymphs, rats, ducks, you name it. I think they pick up more on vibration and profile more than UV signature.

    If you have the ambition to experiment with UV, go for it. Being confident in your patterns pays dividends. If there is a connection between UV and catch rates, I'll definitely jump on board. As it stands, I spend enough of my time experimenting with weights, profiles, and the colors in the visible light spectrum. I try to take the KISS approach to tying flies, but it's not easy to keep things so simple.
     
  6. Jim Wallace

    Jim Wallace Smells like low tide.

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    Can anyone tell me how deep one can go before one can expect UV to lose its effectiveness?
    If the UV effect is reflected off the UV treated lure from sunlight penetrating the water, then it must fade as the depth increases.
    I've been using the "glow in the dark" plastic twirl tails for bottom fish at greater depths (deeper than 35') and toward evening in the shallower spots I fish (15' to 35'), since they emit light, rather than reflect it.
    Large WHITE twirl-tail grubs (6" or longer) on 2 oz jig-heads, or large (6" or longer) reflective holographic swim baits have been my most successful Ling Cod lures here in the shallower depths (15' to 50') I normally fish. Bounced off the bottom, of course.
    I don't use the "glow" lures that often, but when I do, they seem very effective.

    Only 5 weeks left until the Ling opener 3/16 here on the coast!:)

    I might try some UV flies for Black Rockfish this spring/summer, if my arm is ready to cast an 8 wt with a T-14 head.
     
  7. silvercreek

    silvercreek Active Member

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    There is no set answer. Depends on turbidity due to algae, silt, etc. Plus UV means ultra violet, the entire spectrum between X rays and visible light so it has a very wide rand from 10 - 400 nm. The UV spectrum is greater than the entire visible spectrum of 380 - 740 nm. Near UV is what trout can see and that penetrates a bit deeper than the near UV that we can see.

    Since we cannot see UV below 380 nm, we are color blind to UV. Ask any person that is color blind. The absence of a single cone changes the entire color spectrum. They cannot match what they see to what we see. Similarly, we lack the UV cone and we cannot tell by looking at a UV dubbing if it will match what the fish sees.
    [​IMG]
     
  8. silvercreek

    silvercreek Active Member

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    Here's a recent study on UV vision in birds. They have 2 different UV cones that do not overlap and so a bird with one type of UV cone sees colors differently than a bird with the other type of UV cone.

    http://news.yahoo.com/birds-got-uv-vision-131119080.html

    "Birds see color in a different way from humans," study co-author Anders Ödeen, an animal ecologist at Uppsala University in Sweden, told LiveScience. Human eyes have three different color receptors, or cones, that are sensitive to light of different wavelengths and mix together to reveal all the colors we see. Birds, by contrast, have four cones, so "they see potentially more colors than humans do," Ödeen said.

    Birds themselves are split into two groups based on the color of light (wavelength) that their cones detect most acutely. Scientists define them as violet-sensitive or ultraviolet-sensitive, and the two groups don't overlap, according to Ödeen. Birds of each group would see the same objects as different hues.

    http://www.biomedcentral.com/1471-2148/13/36/abstract

    So we see colors differently that a fish that has UV vision and the problem for us is how do we know that the UV material that we put on a fly matches the UV spectrum of the food. Another problem is how much of it do we use. Just like we have different colors of brown or olive depending on what mix of the primary colors we use, we will get different colors depending on the mix of UV in the fly ro the dubbing

    I suspect that much of the UV material really does not match any natural at all. I think it acts as an attractant just like the hot spot on a Frenchie nymph. There is nothing wrong with that since it works but lets not fool ourselves into thinking that we are somehow"matching" the hatch by using UV.
     
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  9. overmywaders

    overmywaders New Member

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    I would like to step in to address some of the issues raised. I'll take them in no particular order.
    • UV penetrates much deeper in water than visible light. It has been documented at a depth of 600m (1800+ feet). SCUBA divers take advantage of this by wearing patches on their wetsuits of fluorescent material which fluoresces in the UV, allowing the divers to see one another even at great depths.
    • Humans can see in the UV as children*; however, as they age yellow pigments build up in the lens of the eye to block the hazardous UV rays. The artist Monet painted differently after his cataract surgery which removed the lens from his eyes. Trout lack the protective yellow pigment but have stem cells that regenerate any "burnt out" retinal cells.
    • The percentage of available UV wavelengths increase at dusk. The night-mating insects such as mayflies have UV vision and UV markings in order to determine the species and gender for their "one-night stand". It is logical that trout will expect the same markings in an artificial as the insects they are feeding upon.
    • Trout lose their UV-specific cones - except in the dorsal temporal region - at smoltification. However, all of the cones have a secondary peak in the UV. Thus trout are constantly receiving UV input. At night the cones are withdrawn and the rods extend. The rods are more sensitive to UV light than visible light.*
    • In turbid water, the UV photons are scattered, providing a light ambient background. A UV dark fly, for example a fly with peacock herl and black hair, stands out against the UV light backdrop.
    • Trout (and birds) get most of their UV in the 365nm range, and virtually none below 340nm. Since many modern digital camera sensors can be modified to this range, we can determine what the insect looks like in the UV and then replicate it with appropriate fly tying materials.
    • Most scientists studying salmonid vision believe that the UV-specific cones are retained or regrown** in the dorsal-temporal region. Flamarique, OTOH, believes that those corner cones shift to providing blue; however, in terms of the UV vision in trout, Flamarique says it doesn't matter, as all the cones have the secondary peak in the UV, so the trout has UV vision regardless. (BTW, salmon returning to freshwater regrow their UV cones.)
    [​IMG]
    In the image in the top left, when a photon of 500nm is absorbed, it can be absorbed and expressed by many different cone opsins. Draw a line from the 500 straight to the top. Every opsin it passes through will be triggered to a greater or lesser degree. However, because 500nm is visible green, the intensity of each opsin should still register on the visual centers as green, with different intensities.

    As well, note the peaks of each cone opsin type. While each cone opsin type has a unique peak, they all have a secondary, lower peak in the UV (below 400nm). So, when any of the cones receives a UV photon of 350nm (the left axis), the visual center should register it as UV. This is wavelength discrimination, the essential element of color vision. And Flamarique's statement holds true. If you look at the graph, the opsin expressed by the SWS2B (blue cone) reaches 37.5% at 350nm; much greater than all the other cones but SWS1 (UV specific).

    * Near ultraviolet radiation elicits visual evoked potentials in children
    George C. Brainard, Sabrina Beacham, Britt E. Sanford, John P. Hanifin,
    Leopold Streletz, David Sliney


    ** Degeneration and regeneration of ultraviolet cone photoreceptors during development in rainbow trout
    W. Ted Allison†, Stephen G. Dann‡, Kathy M. Veldhoen, Craig W. Hawryshyn§*
    Article first published online: 17 OCT 2006
    Journal of Comparative Neurology Vol 499 Issue 5
    also

    Functional mapping of ultraviolet photosensitivity during metamorphic transitions in a salmonid fish, Oncorhynchus mykiss
    Mark E. Deutschlander*, Danielle K. Greaves, Theodore J. Haimberger and Craig W. Hawryshyn 2001Functional mapping of ultraviolet photosensitivity during metamorphic transitions in a salmonid fish, Oncorhynchus mykiss


     
  10. overmywaders

    overmywaders New Member

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    BTW, The paper linked to by the original poster has a multitude of errors. Even the quote

    is incorrect.

    Peacock herl has a very low UV reflectance, as does every iridescent natural material I've tested. Since the color of feathers is a matter of feather structure and not pigmentation, generalizations regarding UVR based upon color don't hold up. There are two subspecies of a particular European songbird (can't remember it now); they look identical in natural light, however, one has a highly UV reflective neck patch, the other doesn't.

    And look at the honesty markings in the golden pheasant crest, below:
    First in visible light:
    [​IMG]

    and now in UV reflected
    [​IMG]

    The crest on the left is from a younger bird and is quite bright in ultraviolet reflectance, the other crest is only medium in UVR; yet both appear the same color in visible light.
     
  11. jwg

    jwg Active Member

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    overmywaders:

    curious to know the light source and filters and camera used to get the image in UV reflected

    jwg (original poster)
     
  12. silvercreek

    silvercreek Active Member

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  13. overmywaders

    overmywaders New Member

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    The light source was natural sunlight through an insulated double-pane window. (yes, there is lots of UV lost by the window, but it was very cold outside).
    The camera was a Lumix GF1 with the ICF and dustshaker removed and replaced with a clear quartz glass over the sensor.
    The filter was a PrecisionU UV bandpass filter - see http://uvroptics.com/index.php?products I developed and manufacture those filters.
    The lens was a Ludwig Meritar 50/2.9 pre-WWII with three elements in three groups.
    ISO was 800 for both. Exposure 1/1000s at f/8.0 for visible; 1.3s at f/8.0 for UV.

    The GF1 has two customizable white balance settings. I used both. The first was WBed for visible light, the second was WBed for UV. A PTFE standard was used for WB setting. The WB of the GF1 also provides a very dependable gamma correction. I have found that the raw WBed image from the camera needs no post processing in most instances.