Monday, July 1, 2013

Human UV vision simulated using reflected ultraviolet UV photography

Today about something very different, still using shots of a decorative flower, a Zinnia haageana - Mexican Zinnia in reflected ultraviolet photography using my "work horse" UV filter, the Baader-U filter but additionally a new, very special XHUV filter, this time NOT for simulating bee and butterfly vision, but to visualize and simulate HUMAN UV vision (hence labeled XHUV). It has been reported since years, that some humans have UV vision, mostly either after cataract surgery where the natural lens was replaced by one that allows UV to be transmitted or because of having aphakia. Some individuals having UV vision are known to me and I am in discussion with them about this ability. This discussion led me to do some tests on myself and it seems that I also have some (limited) ability to see UV light, well not much, and quite blurry, but nevertheless it seems to be there (compared to my wife who cannot see anything at all under identical test conditions). Using my UV sensitive camera I tried to simulate the colors I am able to see as follows using XHUV filter.

*** DO NOT TRY TO REPLICATE THAT HERE, if you don't know exactly what you are doing, as it may harm your eyesight!! ***

Let me explain it a bit further: First one starts looking in the visible at the flower (and taking a normal photograph to document that for comparison reasons), then an UV transmitting filter is held in front of one eye, shielding all the natural light around. Let the eye adapt to darkness and then UV image starts to form. Use a UV LED to enhance that if needed. Then attach to the UV sensitive camera an UV transmitting filter and record in similar fashion when has been seen. Use these two images side-e-side as a diyptych to present the differences in visible and UV vision - this is what I have done here. It is a comparison side-a-side, is is NOT concurrently seen. What I have additionally done is experiment with various UV transmitting filters until I found one that closely simulates what I have seen in UV, that's the now called XHUV filter.

Lens was a Hamamatsu 50mm quartz fluorite lens. Light source for photography was a UV enhanced Xenon flash, for the human tests sun and a UV LED. All photographic shots were done at about f8.

[click on image to see a larger one]

Visible light image, identical to how I see it:  

UV image using Baader-U filter (approx. 320-395nm, effective peak approx. 375nm) as my UV camera sees it:  

UV image using XHUV filter as my camera sees it, quite similar to how I see it (including the blurriness as I cannot get sharp UV focus):  

Diptych to compare visible image with camera UV image:

Diptych to compare visible image with camera simulated human UV image:

Diptych to compare camera UV image with camera simulated human UV image:

Mexican Zinnia flowers have a very specific UV pattern, its petals are very UV dark on the middle and bottom, but its petal tips are very UV bright. Hence why I used that to test out what I would be able to see looking through a UV transmitting filter and then to simulate that using my UV sensitive camera. I hope all this gets nicely visible.

*** Again: DO NOT TRY TO REPLICATE THAT HERE, if you don't know exactly what you are doing, as it may harm your eyesight!! ***

There is a follow up about Human UV vision HERE.

Stay tuned, more will follow on that fascinating subject...

More info on this very interesting field may be found on my site