View Full Version : UV, coatings, fluorescence

15-Aug-2005, 09:35
Having been a sea-level guy all my life I never had to think of UV issues that weren't handled by a simple contrast filter.

But what about being about 15k feet above sea-level? Any special considerations? Do any modern lenses (say, Schneider or Rodenstock lenses made after 1965) have issues with fluorescense?

15-Aug-2005, 09:45
The issue is with the film more than the lenses. Most films are sensitive into the UV spectrum past what's visible, so the blue atmospheric haze that you see at altitude get exaggerated. At 1500 feet UV and deep blue is very strong. Even att just 8000 feet you can see a difference in the light with your eyes; film sees even more of it.

John Cook
15-Aug-2005, 10:52
There is an old “Bert & I” recording wherein a man is asked if he has lived in Fox-Croft Corners all his life. He answers, “I dunno. Haven’t lived all my life yet.”

But perhaps like you, I have spent the bulk of the last six decades in the coastal plain of the North East.

I have “been high” only twice: once shooting in Arizona in 1962 and the other in Colorado in 1969.

In Arizona, the dry desert sky was deep navy blue. It had its own built-in Wratten #29 filter. Open shadows which in Massachusetts are about two stops dimmer than highlights, were absolutely black. Subject luminance range was like the surface of the moon. Don’t leave home without fill flash.

Colorado was in November at the summit of Snowmass Mountain in Aspen. As my family in Penobscot, Maine, is fond of saying, “colder than a well-digger’s butt”. The Hasselblad 500C froze solid. Had to pound it with my fist to get the mirror back down.

Really didn’t ever get around to considering fluorescence. And expect I won’t get the chance in future. I am becoming too fond of being home for lunch after the shoot. ;0)

Bob Salomon
15-Aug-2005, 11:20

Color or black and white?

With color many photographers use stronger warming (skylight) filters like a KR6 or KR9 to filter out the excess blue. These filters are also commonly used in winter at any altitude to warm up the blue in shadows as well.

With black and white films strong UV filters used for aerial work may also be used but these have a strong yellow cast so they must normally be removed for color work.

Ole Tjugen
15-Aug-2005, 11:35
I haven't shot colour slides higher up than 2200m (about 7300 ft), but didn't notice any problems with excessive blue.

The only places I've noticed extra blue is right here, near sea level in western Norway. But that is more due to very blue skies (when it's clear) and deep shadows in narrow valleys.

I haven't heard of any lens, regardless of age, with fluorescent elements!

15-Aug-2005, 13:26
Ole: "I haven't heard of any lens, regardless of age, with fluorescent elements!"

Well, your life isn't over. You may yet learn of a lens that fluoresces under UV, unless Norway has different physics than the rest, which I could believe. My ex was Norwegian and her logic was from the Far Side.

15-Aug-2005, 15:49
"Don’t leave home without fill flash."

Are you talking about color transparencies?

I've done a lot of black and white work in the desert southwest in midday sun and had no problems ... but trannies might have been nearly impossible.

I also suspect some of the lower contrast color neg films (like NPS) could handle that hard light pretty well.

15-Aug-2005, 15:50
You migh also check out rockclimbing.com

there's a photography forum there. not everyone's a rock climber ... there are plenty of alpinists with experience taking pictures at some really terrible atlitudes.

Jim Rice
15-Aug-2005, 18:07
I thought it was a witch's tit.

Struan Gray
16-Aug-2005, 01:05
Optical glass doesn't fluoresce. Or rather, if you could pump in enough UV to see the fluorescence you would also see a red glow from the glass getting hot and the emulsion would be toasted and crispy.

I've climbed to 6000 m and just made do with a skylight filter. People - especially climbers - expect altitude climbing pictures to look a bit blue, so I wouldn't overdo the corrections. Even at 6000m there can be cloud cover, so if you really care about colour casts you will have to carry a colour meter and a whole set of correction filters. Alpine flowers can come out very funky on film, but that's the same 'anomalous reflection' problem you get in bright sunlight at sea level, and the cures are the same.

16-Aug-2005, 08:54
Where were you at 6000m, Struan? do you still climb?

16-Aug-2005, 11:46
Struan said: "Optical glass doesn't fluoresce. "

I'll have to find the specific reference - it wasn't to the glass, but a certain cement used between lenses that supposedly fluoresces under UV. Maybe it was just hogwash.

(Get the lens yet?)

Struan Gray
17-Aug-2005, 00:48
Paul, I went to the Biafo Glacier in the Karakorum in '87. We stayed a tad under 6000m to avoid peak fees, picking unclimbed peaks off a map drawn by Shipton in the 20s. The highest is called Ghur, bang on 19k feet, and is quite impressive from the K2 walk in along the Braldu valley (now a jeep track). We nipped round the back and up from the Snow Lake side. There's a picture of me on the top in the '87 or '88 AAJ.

Great fun. I get a lot of wierd joint pain these days, and crick my neck at the drop of a hat. That puts me off doing the sort of alpine and winter routes that I really love - a spasm half way up would not be fun for me or a partner. The Itch is still there, and I surreptitiously boulder when I think fate isn't looking, but I'm keeping my skills in reserve until my kids grow up a bit and we can go cragging together.

JJ(s): you have more nicknames than Old Horny. I got a slip from the PO yesterday, but that might be books from Photoeye. Rest assured, I'll let you know.

Any non-metal will fluoresce if you hit it with enough short-wavelength UV. The important question is the fluorescence yield: what proportion of the incoming light produces a fluorescence rather than just heating the material. Optical materials are usually chosen to have as low a yield as possible, partly because the light from the fluorescence can cause problems, but also because a strong fluorescence has effects on the material's optical dispersion that make it hard to tame chromatic abberrations.

17-Aug-2005, 08:11
The joint pain must be a drag, but it sounds like you earned it. If I ever go to the himalayas or karakorum, that's the exact kind of trip I'd like to take ... avoid the crowds, peak fees, and outrageous altitudes of the famous peaks, and do something fun and new.

Struan Gray
18-Aug-2005, 00:50
I wouldn't have turned down a chance to take a crack at the Abruzzi Spur, but the lightweight, pioneering approach has a lot more to offer if you like the mental aspects of mountaineering. I still have a ticklist of winter routes in North Norway and first ascents in the Bogda Ola to complete, so if I can tame the twinges I may 'go high' again. That said, climbing for me was always an intensely aesthetic experience (which always baffles those who can only think in terms of pitting yourself against the mighty mountain) so I'd settle for trekking with a LF outfit - and about a thousand porters to carry necessary supplies like film, caviar and Bollinger.