New UV lamps for Ultraviolet photography

Madatec srl  is an Italian company supplying scientific imaging and analytical equipment. We have been in touch for a while since they serve the art diagnostics and conservation sector and, such as CHSOS, it has a keen attention on exploring innovative low-cost solution. My contact at Madatec is Davide Manzini, their expert on Imaging and Spectroscopy equipment. He was inspired by a post I wrote and he was interested in developing a UV lamp for the cultural heritage sector. We had a bit of talking about it and eventually he told me it was done; “Antonino, interested in trying our new UV lamps?”  Of course, you know the answer.

First look. Definitely, they are long overdue tools.  You can have a look at them here. These UV LEDs lamps come in 2 varieties, one is called  CR-UV Viewer and the other CR230 . There are obvious reasons why to use LEDs rather than the wood lamps. In this post I provided some info on lamps for UV photography and I introduced a good UV LED lamp. Though, at that time I noticed that it was a pity the LEDs where not filtered. Indeed, even if this generation of LEDs is centered at 365 nm, they have a purple visible component which limits the quality of the UV image. This visible component can be easily filtered out applying a UV-pass only filter as the BW 403 used for UV Reflected photography (UVR). On the other hand they can be bought with specific dimensions from optics vendors or now it is possible to purchase, eventually, a powerful filtered LEDs lamp, as the CR-UV Viewer or the CR230. Some other features: they are very sturdy, got a metal frame; relatively compact with a total length of 30 cm (~1 feet) for the  battery operated version and just 20 cm for the power cord operated lamp (CR230) . On the website it is available the emission spectrum for the CR-UV viewer.


pigments checker v2 vsPigments 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’.


ultraviolet fluorescence photography

Testing the CR-UV Viewer (top left) with the pigments checker (middle) and the UV meter (right).

 

Ultraviolet LEDs lamp

The compact model, power cord operated CR230

Power output. I wanted to compare these two new lamps with the UV lamp I currently use. I have a Xenopus Electronix HighFlux 365nm LEDs. As I mentioned above this lamp has a strong visible component which I filtered out using a UV-pass filter that I took from another lamp, one of those using mercury bulbs.

365nmFiltered

Xeno­pus Elec­tronix High-Flux 365nm LED lamp filtered with a UV-pass filter.

 

I compared the power output of the two lamps measuring the amount of UV light that the lamps deliver. I filtered the UV meter in order to avoid any visible and infrared contamination with the BW 403 (Vis blocking filter) and CC1 (Infrared blocking filter).  The first thing to notice is that the Xenopus Electronix HighFlux 365nm LEDs has an emission angle less than 90 degree since it mounts special lenses on its LEDs to provide a UV spotlight. The UV lamps from Madatec do not mount lenses, in order to have a more uniform illumination, and their emission angle results about 110 degree. Consequently, while at close distance (few tens of centimeters), the emission of the CR230 is comparable with that of the Xenopus, at higher distances  the CR23o irradiates a much bigger area with less intensity.    For example, on a target at 150 cm, this is roughly the distance I keep when doing UV fluorescence photography on a medium sized painting, the UV meter gave  a value 70 uW for the Xenopus Electronix HighFlux 365nm LEDs,  10 uW for the CR-UV Viewer and 15 for the CR230, as a consequence of the higher area of irradiation.

Light quality Madatec loaded on its website the emission spectrum of the lamp which shows the visible component is effectively filtered. I did want to test it with the pigments checker to evaluate any difference between the filtered Xenopus Electronix HighFlux 365nm LEDs and the CR-UV viewer as far as concerned the excitation of the pigments’ fluorescence. I shot two photo with the same conditions (lens, distance lamp-target and aperture). I just changed the exposure, 2 sec for the Xenopus and 15 sec for the CR-UV Viewer. No difference can be appreciated.

madatec UV lamp

The two photo where taken with the same conditions just the shutter speed changed (2sec for the Xenopus, 15 sec for the CR-UV).

Pros

  • Sturdy
  • It has plugs for both ¼ and 3/8 tripod threads.
  • The illumination is awesomely uniform. This is actually the main feature I appreciate in these lamps. Madatec chose to guarantee a uniform illumination over a spotlight configuration. For example at 70 cm the Madatec lamp illuminates an area 1 x1 m while the Xenopus an area about 35 x 35 cm.
  • It is an off-the-shelf already-filtered UV lamp. Convenient if you don’t want to tinker with filters.

Cons

  • The power of these lamps, both Madatec and Xenopus, it’s not enough for big surfaces; such as if you want illuminate at once a fresco from the floor or a big painting at once. Then there are more stronger lamps.

Suggested applications. Definitely these two Madatec UV lamps are useful for documentation of relatively small objects, such as historical documents (prints, purchaments,..) For these applications you would appreciate the excellent uniform illumination and the power of the lamps is just fine to obtain perfect UV fluorescence images.

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2016-10-17T16:33:21+00:00

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