are several different types and as many different qualities
of UV Black light units on the market. Generally speaking
they fall into 3 main types:
Vapour Lamp - Used in large UV
Projectors such a UV Canon and a UV Flood.
Fluorescent Tube or Bulb - Most
widely used form of affordable Black light.
UV LED based
- LED Torch or Flashlight versions.
Holy-Grail of UV lighting is to produce a pure
365nm UV output with Zero Visible Light
Interference. As this is not yet practical (or
affordable), so let price be your guide as to
how close your choice of UV light will come to
The more visible light you see, the worse the UV
quality will probably be.
applications a certain amount of visible UV glare is
acceptable which makes the basic UV units affordable.
tube based black lights generally produce the best results
when compare with LED based alternatives. However, they only
offer a short effective working range (illumination
distance) and require mains-powered operation to deliver
their best results, both of which limits their use and
and Flashlights generally produce a strong 'UV beam' best
suited to illuminate 'at a distance' and are not usually
suited to close-up work, owing to the higher visible-light
'interference' output, which tends to mask (or suffocate)
the resulting fluorescence.
Forensic Torch with a lower visible output, may be used for
both close-up and distance work
Let price be
your guide and do not buy cheap UV LED torches expecting
Lots of visible 'Purple light' is usually an indicator of
POOR UV Quality!
test below will enable you to find out into which frequency
band your UV Torch belongs...
Products Fall Into 3 Categories
POOR QUALITY (Frequency
Range: 390 - 405nm)
operating in the wider 390nm - 405nm range generally use
poor quality 'cheap' UV LEDs which produce far too much
unwanted visible 'purple glare' (interference) and far too
little in the way of a useful UV light.
rule-of-thumb is the more LEDs the torch has, the lower the
Quality of UV produced. Avoid torches with more than 9
Range: 380 - 385nm)
outputting UV in the 380nm range perform much better and
produce superior results, with a much reduced 'visible'
(interference) output. Such units will naturally be more
expensive than the cheaper 390-405nm models.
(Frequency Range: 365 - 375nm)
contrast, the higher quality, more expensive torches
producing the 365nm wavelength, produce a near pure UV
output which is the optimum frequency for UV fluorescence.
This means you will see far more detail and in a greater
range of colours than any other wavelength. As these units
generate less unwanted Interference light, they may
naturally appear weaker or darker. This can be misleading
and should not be misinterpreted.