Ghosting - what causes this ?

[Panza]

I was at the tivoli yesterday and took some pictures.
I would have been quite happy with this one if it hadn't been for the ghosting or what it is called.

http://wrc-cosworth.org/dv/ill/Tivoli01.jpg

Camera: D30
Lens: EF 17-40L: 40mm , f4 , 1,5seconds , Av.

What is causing this ?
I have never seen this before but I have never used the Canon UV haze sharp cut filter before either..

[drisley]

The UV filter is to blame.
It's a good idea to remove the UV filter when shooting nite shots. Or, do what I do...never use a uv filter, just lens hood all the time.

[RichardtheSane]

Just to ditto what drisley said.
Looks very much like ghosting from the UV filter.

[drbls]

I wouldn't go quite so far as to blame the uv filter, but it might have contributed. This ghosting is actually an internal reflection due to light bouncing between the elements in your lenses. Look carefully...the image is exactly across the lower left to upper right center diagonal axis of the photo from the bright spinning carnival ride. This is the same effect seen when shooting into the sun. The multiple copies of the sun (sun spots) are from internal reflections off the elements. Now, L glass is supposed to reduce the reflections somewhat, so the filter might have played a role. In general, the more elements in a lens (especially zoom lenses), the greater the chance for reflections.