A couple of thoughts:
1. You will need to know the spectral output of the LED lighting (where the
UV is occurring, is it a narrow "spike" or a broad "hump")
2. You will need to know the spectral response of the various UV & skylight
filters available which are probably different for different manufacturers
and may actually have changed from time to time depending on manufacturing
techniques and materials.
3. Match the filters to the LED lighting and evaluate the results
4. The "problem" you mention regarding fluorescence (glowing shoes and
likely the stage makeup) can only really be solved by filtering out the UV
before it reaches the fluorescent pigments/dyes, that is filters on the LED
lights themselves which presents another problem - you will need to provide
additional lights without the filters if for some reason you really want to
provide black light effects.
...Wayne
-----Original Message-----
From: olympus
[mailto:olympus-bounces+wayne.harridge=structuregraphs.com@xxxxxxxxxxxxxxxxx
] On Behalf Of Ken Norton
Sent: Saturday, 19 November 2016 3:38 AM
To: Olympus Camera Discussion <olympus@xxxxxxxxxxxxxxxxx>
Subject: [OM] LED Stage Lighting and UV
A couple weeks ago I wrapped up a contracting job where I sold and installed
a sound system, stage lighting and large flat-screen tv system for a
multi-purpose rental venue. For the stage lighting, I installed full-color
LED lights. The lights use those combo multi-color LEDs. Some are four
channel (Red, Green, Blue, Amber) and Some are six channel (Red, Green,
Blue, Amber, White, UV). The UV channel provides "black light"
functionality.
One of the battles every photographer has fought is LED stage lighting and
how hard it is to photograph in it without clipping. And, depending on the
camera, you'll get really horrible color casts. This is one of those cases
where film actually is far superior than digital for capture.
But why?
I think I figured out part of the problem. The LED lights produce copious
amounts of near-UV light. (I wear bright neon colored shoes, so it was easy
to see the black-light effect even with the UV channel turned off). Most
digital cameras, to one degree or another, have a secondary sensitivity bump
down right near the UV end of the visible spectrum. In the case of the
classic E-1, this secondary bump is present in the red channel. This way, a
violet colored subject will capture as purple, whereas some cameras (and
films) will capture it as blue. Older Nikons were especially prone to the
blue-shift to an extreme.
At issue is how the camera sees and captures this near-UV illumination
caused by LED lighting. I'm noticing a general color fogging that can't be
mapped out during raw conversion. If a person is wearing stage makeup, the
result can be that it looks like you yanked the Clarity Slider backwards 50
points and has a Trump-color to the skin.
No stage makeup and you'll get green-blue pastel zombie apocalypse.
Now, understand that I almost never use skylight or UV filters on my lenses.
They go commando. It may be that for LED stage lighting, I need to try using
a UV filter.
Thoughts?
AG (purple and glowing) Schnozz
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