Photography Light/Polarisation

[Satori_001]

A friend of mine recently took some photos in Paris at night of the sites. Using a slow shutter speed on a Panasonic Lumix FZ5. In some of the photos (at distance) you can see trails of lights from cars which are apparently moving in a spiral motion, increasing in amplitude the further from the source (car) they get?

Someone please explain?

Many thanks!

[gen2]

That has nothing to do with light polarisation. It is to do with camera movement during the exposure. I could be more specific if I knew:
(a) just what the exposure time was and how many oscillations of the light are visible.
(b) was the camera mounted on a tripod or hand held?
(c) what was the ground beneath your feet?

There are many possible sources of movement:
(1) Vibration/movement caused by pressing the shutter.
(2) Human movement - breathing / pulse.
(3) Transmission of vibration from machinery through a rigid floor.
(4) Movement of whatever you are standing on (eg boat bus).
(5) Wind.

[8733mags]

The answer above is superb...just a tip.if taking photos at night set the self timer up and before you press the shutter hold the camera against a street lamp post or bridge parapet ...something solid. Press the shutter release...clamp camera and hold it still....the timer times out ...the shutter opens....wait.... the shutter closes and you can get good picture that way......or buy a tripod!

[Satori_001]

satori_001 - further info

Exposure time = 8secs

A tripod was used!

The ground generally tends to be quite stable

Attempting to make said photo viewable

[Satori_001]

SATORI_001 (more info...)

LINK TO THE PIC

http://kardjiev.googlepages.com/home

Also the timer was used.

[gen2]

Thank you for posting the photo. I have deduced that it is a view of the Ecole Militaire seen across the Champ de Mars. Yor viewpoint is higher than the Pont d'Iena and to get that view between the legs of the Eiffel Tower, you must be at the Palais de Chaillot with a long telephoto lens. I see your EXIF data gives a focal length of 47mm but I don't know what that translates into in 35mm terms (300mm maybe?)

At such long telephoto settings any slight movement will be exaggerated. The oscillations seem very regular and are therefore almost certainly of mechanical origin. Their frequency is estimated to be greater than 10 Hz and the motion is circular. During the time of the exposure the amplitude diminishes.

There are therefore two possibilities:

(1) The camera/lens/tripod system has a natural resonace frequency of around this value and takes several seconds to damp off. The original impuls causing the vibrations could be from the setting-up process or from the pressing of the shutter. If this is the cause, then you can confirm it by using the same system and setting it up elsewhere to take similar views of moving distant car lights. Somehow I rather doubt that this hypothesis would produce such high frequency vibrations.

(2) Vibrations are being transmitted to the camera system from an external source. Any motor, engine or pump nearby could be the source. The fact that the amplitude diminishes during the 8 second exposure could indicate that the source of vibration was moving away from you. I therefore suggest that one possibility is that there is a Metro line running somewhere nearby and that the passage of trains is causing vibrations.