Human UV (ultraviolet) vision ?

kds315* · Expire: 2021-03-09

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 lableled 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 http://en.wikipedia.org/wiki/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 replicate the colors I am able to see as follows.

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.

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 vision image:

Diptych to compare camera UV image with camera simulated human UV vision 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'm sure many other people have this ability, yet just don't know about it...

Orio · Expire: 2012-12-04

Fascinating, Klaus! Thanks for sharing.
I'm not sure to understand however, how can you see the flower normally (Yellow) and UV at the same time. Confused

cooltouch · Joined: 15 Jan 2009 Posts: 9097 Location: Houston, Texas

I too am intrigued by this. Do you really see a yellow flower as purple? The dark areas in the UV image show as slight orange areas in the visible spectrum photo, and if by blurry you are referring to these orange areas, then I would agree -- I can't make out distinct edges to the orange, especially the way they appear in the UV images.

Still, I'm wondering how one would see the UV and visible spectrum at the same time. Given that UV is past the violet end of the spectrum, I would expect anything that is UV to have at least some sort of purple cast. There is none in the visible spectrum image.

mo · Expire: 2016-07-30

hoanpham · Expire: 2015-01-18

i guess that human needs a strong source of UV light to able to see some weak reflection?
Interesting that our eyes can be modified!

kds315* · Expire: 2021-03-09

kds315* · Expire: 2021-03-09

philslizzy · Joined: 07 Aug 2012 Posts: 4748 Location: Cheshire, England

I understand how kds315* sees the flower, I think I have it slightly in my left eye and while both eyes are open the brain fuses the two images together and gives an approximate idea of the colour. But when looking at it through my left eye only things are a little different.

As a painter I mix colours to how I see them in life and I am often accused of getting them wrong even though they look identical to me. I have never studied this phenomena, its been with me all my life and kds315*'s UV vision, I think, could explain what it is.

Violet and blue coloured flowers are notorious for being difficult to photograph in their natural colours (for me) everyone says the colours are the same in the photo but to me they are different.

Perhaps this is what we commonly refer to as colour blindness, common in men.

edit: Oh, and I too see different shades of light and dark in a 'solid' colour on a flower with my left eye, although very slight. I have severe astigmatism in both eyes and i've always put it down to that.

A very interesting and enlightening post. Thank you.

kds315* · Expire: 2021-03-09

Yep, maybe this IS indeed the reason why you see colors differently!

kds315* · Expire: 2021-03-09

Have added a 2 dioptries (f=500mm) calcium fluorite diopter lens to my test setup, now the image is sharper...

left: before; right: after (simulated what I see using my UV camera + filter)

LucisPictor · Expire: 2013-12-03

Can it be possible that you can even train that?
So that human eyes can "see" UV to a certain extent but the brain doesn't and that you can train your brain to "see" (=accept) it?

That would make sense because Klaus has so much practise with UV light.

I believe that the human brain / senses can do much more than we all know...

visualopsins · Expire: 2025-04-11

Now I wonder if my short-sight is due to my eyes focusing on UV instead of more visible part of spectrum!

On very clear-sky bright sunny days I see much better without glasses. Maybe not related, on cloudy days I see a BIG increase in color saturation, and focus better without glasses than other times without.

I have terrible time trying to match colors in photos to what I see -- most evident in trying to match colors in paintings and photographs of paintings.

Alex H · Joined: 25 Dec 2011 Posts: 344

Klaus, thanks for sharing. Very interesting!

visualopsins · Expire: 2025-04-11

I wonder too much. Wink

Now I wonder about results from human test in a dark room. Tester retinas get plenty of time to accumulate maximum rhodopsin, then switch on UV led, what do they see, anything? I think maybe good results because rhodopsin has such great sensitivity to low light, into UV wavelengths... In a dark room without Vis to compete, do eyes focus UV properly?(!).

JCDowdy · Posted: Fri Aug 09, 2013 6:18 am Post subject: Seeing UVA-1

Normal human visual range, photopic response spectrum, is known to overlap the UV from about 385 - 400 nm. Older eyes see less of this overlap. nonUV blocking IOLs of course skew this to shorter non physiological wavelengths.

You mignt find this interesting (I did): http://neuronresearch.net/vision/files/tetrachromat.htm

kds315* · Expire: 2021-03-09

visualopsins · Expire: 2025-04-11

So much for my theory. Laughing

Awesome work Dr. Schmitt! Thank you!!!

visualopsins · Expire: 2025-04-11

kds315* · Expire: 2021-03-09

Most welcome Wink