One of the challenges with the reproducibility and comparability of UVL results include the wide variation of UV radiation sources available. UV sources have a different wavelength output (peak and distribution), filtration, and intensity,
which all will impact the color and intensity of the resulting luminescence and the photographic recording of that luminescence. In addition to differences in peak and distribution, some UV sources may also have stray radiation outside
the UV region, including visible and IR radiation, which will impact the results and possible interpretation of the results. This would would be the reasoning for the recommendations for the 2E and 918 filters. Another consideration is the spread and evenness
of the illumination as the UV radiation sources come in all shapes, sizes and intensities.
In addition to the UV sources, the camera and image processing will also influence the final results. There are different recommendations for the processing (AIC Guide to Digital Photography and Conservation Documentation,
UVInnovations workflow, and the CHARISMA Multispectral Imaging User Manual).
The UVInnovations target helps to improve the reproducibility and comparability. There are some great resources on the UVInnovations site including workflows, equipment and some of the studies that they did to develop the target. One challenge with this
target is that the results do not necessarily match with the visual perception of UVL or previous UVL imaging results, which relates to the radiation source, differences in human vision and variation in the camera and position. It is also calibrated with a
UVA source with a single peak near 365 nm, and this relates back to the wide variation of UV sources being used. The target has some limitations when trying to record weak luminescence.
As an aside for the reproducibility and comparability, it is critical to include information about the setup and equipment (i.e., radiation source, filters, and processing) in the metadata since these components significantly impact the results and are
important for interpreting the resulting luminescence.
Best,
Keats
E. Keats Webb
Doctoral Student
Hi Halvor,
The chart sounds like it might be a good idea and I’ll have a look at the filter you mentioned.
Many thanks,
Sam
From: AHFAP, for image professionals in the UK cultural heritage
sector [mailto:[log in to unmask]] On Behalf Of Halvor Bjørngård
Sent: 07 November 2018 09:58
To: [log in to unmask]
Subject: Re: Basic UV Photography
We have been using the solution from UV innovations with the target you link to for a while now. This solution is easy to use and you get consistent results with it, meaning
for different paintings the fluorescence effect vil be comparable to each other in intensity. Images we get is a lot better now than how we used to do it earlier ..
Only difference we did, due to an insistent konservator :-) was that we have gone with this filter:
Normal photographic uv / ir filters blocks by absorbing the rays. But the filters has some elements that also has fluorescence so the filter itself affect the results
by producing some fluorescense. This filter blocks UV / ir by reflecting the rays so there is no fluorescence from the filter itself. I am not certain how much effect this is, but there has been written a couple of articles about this effect.
We use this with a Phase one iq180, have only tried this solution.
Halvor Bjørngård Dr.Eng.
Photographer, photo section.
På 6. november 2018 kl. 16.36.16, Sam Drake ([log in to unmask])
skrev:
Hi All,
I’ve recently been asked to do some UV photography of a collection of works on paper- I’m hoping someone might be able to give me some advice on very basic UV photography.
Up until now our conservation department have been doing their own UV photography with some UV tubes and a point and shoot camera with no added filtration in a far from ideal studio environment. The results have been ok for them as working resource but I’m
quite keen to improve the quality of the images :)
I’d be using the same UV tubes but in a more controlled environment.
In the past for a previous job (if I remember rightly) I used a 2e filter on the front of the camera and some UV tubes. Does this seem like a reasonable way to proceed?
Should I be using a 18A or equivalent filter as well?
One website I’ve been looking at recommends a 2e and a PECA 918 filter- would this be better?
http://www.uvinnovations.com/getting-started
Would it be best to use a Phaseone with a CCD IQ180 back or (because of the low light and long exposures) a Nikon D810?
Previously the conservation department I worked with wanted the colour temperature set on tungsten because they found it easier to see how the different surfaces were fluorescing- is this common practise?
Does anyone have any experience of using a target similar to this and is it worth the expense?
http://www.imagescienceassociates.com/mm5/merchant.mvc?Screen=PROD&Store_Code=ISA001&Product_Code=TUVUVGC&Category_Code=TARGETS
Many thanks,
Sam
Sam Drake
Photographer
National Galleries of Scotland
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