According to D.M. Procida :
The pictures themselves are great - but the camera (Pentax K100D) makes
an absolute racket.

There's a bit of noise during the exposure itself, but afterwards, while
I presume the camera is processing it, it sings and coughs to itself at
length. Is this normal?

Also, it seems to take the camera as long to process a 30-second
exposure as it does to take the picture itself (i.e. before the camera
is ready for further action). Why should this be the case?

Well ... based on the Nikon D70, the default mode for long
exposures is "Long exp. NR" mode, which takes a second "non" picture with the same
exposure time as the actual exposure, but with the shutter closed. This
gives the camera a reference for the noise patterns for that length of
exposure at the temperature at which the camera is being used. This is
then subtracted digitally from the actual image, making for a much
better image than if you turn the NR mode off (which I do when shooting
fireworks, since I am more willing to live with the noise than to lose
the ability to take another shot right away.

Your camera may also offer a way to turn off the NR mode
(whatever they call it), and you should experiment with shooting two
long-exposure shots (one with and one without) just to show you what the
difference in appearance is, so you can know when you can live with the
noise as a tradeoff for the ability to shoot another exposure soon after
the first.

Enjoy,
DoN.
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