Hi Henry,
> is there a trick to guess and visualize the flicker rate of lamps with
> the digicam?
>
What do you want to vizalize? The flicker frequency is known in all
lamps, it is always the double of the operation frequency. If the
operation frequency is not 50Hz (as in lamps with electronic ballasts,
the operation frequency is given in the manual) the light intensity is
additionally modulated with 100Hz.

The only thing that is unknown is the modulation depth: How dark does
the lamp get.
You can vizualize this by taking fotographs of the lamp with exposure
time 1/1000 sec and fixed aperture and iso.
See fotographs here: http://www.testudolinks.de/lichtwiki/roehre/flackern
and here: http://www.testudolinks.de/lichtwiki/hql/flackern

But Reptiles won't see flicker when you don't see it. I found no
evidence that their flicker sensitivity is better than ours. See here:
http://www.testudolinks.de/lichtwiki/vis/flicker
The website is only German, but klick on the [number] and you will be
forwarded to the original scientific article in my literature database,
all of them are in English

Sarina