Ultraviolet Photography: lighting

This post is all about lamps for UV photography.

Studio Photography. UV Black light tubes

If you work in a studio you will probably need just 2 UV fluorescent tubes. They are very cheap and you can mount them on any fixture for the normal visible light fluorescent tubes. Choose fixtures whose materials are not UV fluorescent. These tubes are very economical which means you can have more than two and have as much UV lighting as you need. Drawbacks: since the tubes are big there is no way to filter out their violet visible light and infrared light. This is not a big deal if your examination is limited to detect inpaintings (which will look darker than old paint and varnish). Though, the violet light will not allow you to appreciate the subtle UV fluorescence colors from old paints and varnishes.

We do run a lot of initiatives, Stay on top of things!

My first UV lamp. Sirchie TigerUV

I do provide on-site art examination and documentation with, what I call, lightweight-low-cost-Ryanair-approved-luggage plan. So, being light, for my specific work, is mandatory. For a couple of years, until last month, I used the Sirchie TigerUV lamp. This is a spot light and is much more compact and lightweight than UV fluorescent tubes. It’s a 150W Mercury vapor lamp with internal ballast and long wave filter cover. Weight just 2,4 Kg and has a sufficient UV lighting: power density 4000uW/cm^2 at 15”. This is enough for  “light painting”. Indeed, since this is a spot light you don’t have uniform lighting over a painting so you have to quickly move the lamp during a long exposure, generally between 5-8 seconds, in order to have a final uniformly UV exposed image.

ultraviolet fluorescence, ultraviolet photography, paintings conservation, paintings authentication, Technical Art Examination coins, prints, drawings, stamps, manuscripts, wall paintings, pigments

Sirchie TigerUV. My first portable UV lamp for on-site documentation. It has inside a mercury lamp and the VIS light cutting filter.

Super lightweight. High-Flux 365nm LED

2,5 Kg were too heavy though, so I purchased the Xenopus Electronix  High-Flux 365nm LED fixture. Actually, my friend Filippo in Florence told me about this product. He’s really good at searching the internet for new products and has much more patience than me. Xenopus lamp mounts 3 high-flux Nichia 365 nm LEDs, providing output power 3x325mW at 365 nm which becomes output power density 5000uW/cm^2 at 15”. This is the magic; at a lower weight (0,5 Kg) we have a higher UV light output than the 2,5 Kg Sirchie TigerUV.

The advantage of UV LED lighting are obvious:

  • Instant start up. No more waiting between re-starts, like with the UV bulbs, such as Sirchie Tiger UV.
  • No heating up.
  • Very lightweight (0,5Kg) and very sturdy. When traveling, sturdiness is something you really look for.

It has only one drawback, it’s a bit overpriced, but definitely a great product.

Xenopus Electronix High-Flux 365nm LED. ultraviolet fluorescence, ultraviolet photography, paintings conservation, paintings authentication, Technical Art Examination coins, prints, drawings, stamps, manuscripts, wall paintings, pigments

Xenopus Electronix High-Flux 365nm LED. The perfect UV light solution for on-site art documentation.

No posts could be found that matched the specified criteria.

Enhancing the Xenopus Electronix High-Flux 365nm LED

The Xenopus lamp is small (7×9 cm) and it becomes easy to filter out the violet visible component of the UV LEDs. Indeed, UV LEDs, though centered at 365 nm, they still have a violet light component. It’s not overwhelming, but you want filter it out to appreciate subtle fluorescence.

This site shows nice spectra of the Nichia UV LEDs emission tailing toward the violet.

I made my Xenopus Electronix  LEDs lamp a very only-UV-light  lamp using the same VIS (cutting off) filter from my retired Sirchie TigerUV lamp. On eBay you can find a number of used lamps such as the TigerUV whose filter will work just as fine.

Xenopus Electronix High-Flux 365nm LED. ultraviolet fluorescence, ultraviolet photography, paintings conservation, paintings authentication, Technical Art Examination coins, prints, drawings, stamps, manuscripts, wall paintings, pigments

The longwave filter from the Sirchie TigerUV fits the small Xenopus Electronix High-Flux 365nm LED and cut off the violet visible emission from the Nichia LEDs.

Let’s see some examples. I stamped my hand on my living room wall and took some UV pictures with and without the VIS (cutting off) filter. The difference is dramatic. I wonder why Xenopus don’t sell the lamp with that kind of filter already mounted on, since, I guess, their main market is forensic.

ultraviolet fluorescence, ultraviolet photography, paintings conservation, paintings authentication, Technical Art Examination coins, prints, drawings, stamps, manuscripts, wall paintings, pigments

UV fluorescence photos of my left hand fingerprints on my living room wall. A Visible cutting filter dramatically enhances the image quality.

Let’s see what happens with pigments.

ultraviolet fluorescence, ultraviolet photography, paintings conservation, paintings authentication, Technical Art Examination coins, prints, drawings, stamps, manuscripts, wall paintings, pigments

UV fluorescence photos of 3 white pigments. A Visible cutting filter dramatically enhances the zinc white yellow fluorescence documentation and overall true fluorescence colors.

Spectroline MiniMAX UV-5F Short-Wave

UVF254 is the acronysm for UV fluorescence excited by a short wave UV lamp (254 nm). There are not LEDs at these short wavelengths so we still need to use mercury lamp. There are just small hand-held lamp on the market that deliver about just 5W. Though, it is fine to work with this low power since UVC radiation is harmful for eyes and skin, please read this before use UVC lamps.

I use a Spectroline MiniMAX UV-5F Short-Wave Hand-Held UV Lamp. UVC 254nm unit complete with LONGLIFETM glass filter. UVC light excites fluorescence that UVA lamps (365nm) don’t; some examples are given in the posts on madder lake and on postage stamps.

Spectroline MiniMAX UV-5F. ultraviolet fluorescence, ultraviolet photography, paintings conservation, paintings authentication, Technical Art Examination coins, prints, drawings, stamps, manuscripts, wall paintings, pigments

Spectroline MiniMAX UV-5F. A practical UVC (254) lamp.

UVR 254?

As a note, we cannot do UV Reflected with the UVC (254 nm) lamp since the digital camera detector can see UV light until about 350 nm.

 The Infrared tail

UV fluorescent tubes and mercury bulb lamps, such as Sirchie TigerUV have a sizable IR emission.

ultraviolet fluorescence, ultraviolet photography, paintings conservation, paintings authentication, Technical Art Examination coins, prints, drawings, stamps, manuscripts, wall paintings, pigments

UV fluorescent tubes exhibit IR emission.

This IR emission doesn’t affect Ultraviolet Fluorescence photography, if the X-Nite CC1 filter is used together with the BW 420 (UV Fluorescence) and BW 403 (UV Reflected) to cut off that IR reflection. The UV 365 nm Nichia LEDs have another advantage here. They have a negligible IR emission.

Nichia 365 nm LEDs. ultraviolet fluorescence, ultraviolet photography, paintings conservation, paintings authentication, Technical Art Examination coins, prints, drawings, stamps, manuscripts, wall paintings, pigments

Nichia 365 nm LEDs turn useful also for UV Reflected since they have a very small IR emission.

[ws_table id=”4″]

CHSOS newsletter

2016-10-17T16:34:44+00:00

2 Comments

  1. Moshe March 25, 2013 at 9:54 am - Reply

    Thanks Antonino. Very useful. I’ve been recently doing some UVR and UVF imaging and have run into problems finding suitable lighting.
    Moshe

Leave A Comment Cancel reply

Time limit is exhausted. Please reload CAPTCHA.