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.
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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.
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.
Pigments Checker is for photographers, conservators and scientists interested in technical documentation of paintingss. It has 54 swatches of historical pigments designed for infrared photography, ultraviolet photography and other technical photographic methods for art examination. Check it out!
Pigments Checker is a collection of 54 swatches of historical pigments that have been applied using gum arabic as a binder on a cellulose and cotton watercolor paper, acids and lignin free. This paper is not treated with optical brighteners, it’s slightly UV fluorescent, and it reflects IR. Two cross-hair lines, 0,2 mm (vertical) and 0.4 mm (horizontal) are printed on each swatch of paper before the application of paint, in order to have a means to evaluate the pigments’ transparency in the IR and IRR imaging. Among all the pigments and their varieties ever used in art these pigments collection select the most used ones from antiquity to early 1950’.
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.
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.
Let’s see what happens with pigments.
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.
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.
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.[ws_table id=”4″]