From: Sandy King (sanking@clemson.edu)
Date: 10/27/01-05:31:27 PM Z
Ed,
>Sandy:
> As I understand it, BLB bulbs are simply BL bulbs with a secondary
>coating that blocks visible light. Should this be true (and it can be
>checked by contacting Phillips), the BLB bulbs should not be inherently
>faster unless the visible light portion of the spectrum inhibits printing.
>Something to think about.
I am not at all sure you are correct in this assumption. First, I
have the spectral data or a number of bulbs. There appear to be two
kinds of BL bulbs: one know as the BL bulb with a phosophor that
emits in a very narrow bandwith mostly around 360nm, another called
the 350Bl that has a much broader bandwith, starting around 300nm
with significant tail out to around 420nm, with spikes out to 550nm.
As best I can determine the GE BLB is a filtered BL tube, "not" a
filtered 350BL. The Sylvania tubes that I am using as comparison with
the GE BLBs are 350BL, the one with the broad bandwith.
> Further, I have a spectrum on the super actinics. They give a very
>strong peak at 410 nm which trails off within 35 nm in both directions. No
>secondary peaks. Power means nothing if the light emitted is not within the
>active range of the emulsion.
I also have the spectral data for Super Actinic 03 bulbs. The
phosphor of this tube begins at about 380nm and extends out to about
480nm, with the peak at around 425nm. My spectral data shows a
significant spike at about 575nm, not I imagine of much use to our
processes.
> Thus, comparing fluorescent bulbs with metal
>halides means little unless you have the spectral response of each.
The spectral data chart for metal halide bulbs shows that they emit
all over the place, which is one of the reasons this type of light
can not be used for making color negatives or slides when accurate
color balance is important. However, making direct comparisons of the
printing speed of the metal halide unit with the other lights makes a
lot of sense to me since it is the practical aspect of printing speed
that I am interested in.
Sandy King
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