Earl
>
> Thanks for the warning! It never would have occurred to me, but after
> thinking about it, I think it makes sense. Here's a possible explanation
> of what is going on:
>
> In high school I worked as an assistant for a professional photographer
> and I learned that xenon strobes give off huge amounts of UV light.
> This causes trouble is in wedding photography. It turns out that satin
> wedding dresses fluoresce brightly under UV light! This results in a
> bluish or purple cast to the dress and can really ruin the picture. To
> avoid this, the Pros use a UV blocking filter over their strobes.
>
> The second bit of info comes from an experiment I made to enhance the
> coloration of some my Droseras with UV light. Since sunlight enhances
> anthocyanin production much better than most artificial light, I thought
> that this might be due to the extra UV in sunlight. To test this idea,
> I took a short wavelength UV lamp from a EPROM eraser unit and directed
> the light onto D. capensis plants. The results were devastating. A 10
> second exposure from about 6" distance caused all the tentacles to dry
> up and wither.
>
> Could it be that Michael's strobe was unfiltered, but Barry's had a
> plastic diffuser/filter built-in. A powerful strobe puts out about
> 50-100 watt-seconds of energy which is roughly comparable to my 10 watt
> UV bulb for 10 seconds.
>
> --
> Rick