Tony Cooper wrote:
On Thu, 4 Jul 2013 15:09:07 +0200, Wolfgang Weisselberg
Tony Cooper wrote:

[Fireworks]
Bulb can be used instead of 4 seconds if you have a black card to hold
over the lens and take away the card to capture the burst and then
replace it. This can produce some interesting multiple exposures
because several firework bursts can be recorded on one image.

You can also simply merge several firework burst images. :-)

Yes, that can be done in Photoshop (and maybe other programs)

You probably mean "that can be done in other programs (and
maybe in Photoshop".

by
bringing in additional images as new layers and changing the blend
mode to Screen on all but the Background layer to drop out the sky.

Or simply use additive blending, or "choose the brightest
pixel". (Newer Canons can do that
in camera, even!)

But, not everyone has Photoshop to work with.

Dudley would simply whip up a perl script: choose the brightest
pixel and done. (Or add all pixel values and scale down so
the maximum values don't cross 255.)

Or people could use the GIMP ...
.... or dozens of other programs.

-Wolfgang