Re: Do I need to upgrade to i1Profiler? With respect to UV
Re: Do I need to upgrade to i1Profiler? With respect to UV
- Subject: Re: Do I need to upgrade to i1Profiler? With respect to UV
- From: Graeme Gill <email@hidden>
- Date: Wed, 13 Apr 2011 12:57:21 +1000
Roger Breton wrote:
I don't have data to show (not yet, at least) but I always was under the,
wrong perhaps, impression that the single most disadvantage of tungsten
lighting, relative to D50, was its low UV content. Yet, you write that
typical "graphic arts" fluorescent lamps (aka viewing booths) seem to
exhibit the same low UV energy content as "properly adjusted lamps".
Hi Roger,
you need to distinguish between a tungsten (or any) source in an
instrument, and in a live viewing situation. In the instrument the
illuminant gets divided out to give reflectance. So it's the relative
energy of the illuminant at the FWA/OBE excitation and emission wavelengths
that determines how significant the measured fluorescent effect is.
In a live viewing situation this division doesn't happen, so our
impression is dominated by the greater energy of the tungsten lamp
at longer wavelengths.
In contrast fluorescent lamps have a more balanced spectrum,
just like sunlight (ie. their white points are closer to D50-D60,
rather than the 2800K of incandescent), so the difference
between use as an instrument illuminant and live viewing is
less dramatic.
Fluorescent lamps typically have a phosphor coating that absorbs as
much U.V. as possible, in order to turn it into visible light,
so unless such lamps make special provision (by adding say, a
phosphor that emits at softer U.V. wavelengths), they are usually
very low in U.V.
So for an instrument use a tungsten lamp will show quite noticeable
FWA/OBE effects, while in live viewing these effects will be much
diminished.
Live viewing can be effected greatly by the presence of glass over
various things too - like the light source, artwork etc., since
ordinary glass absorbs U.V.
Graeme Gill.
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