Sigma 24-70 F2.8 - what's this?

Hi All:

I have a new Sigma 24-70 F2.8 DG Macro lens, and have an issue with it. This is NOT the front focusing issue - which by the way this copy does have, and I plan on sending back to Sigma for calibration.

Below is a recent shot with a 20D, this lens, F2.8, 2.5 second exposure, ISO 100. I have noticed this on several different night shots. You will notice the green mirror image ghosting in the sky - I've placed a red bar above the ghosts and below the original lights. You can even see the green ghosts of the strung, hanging lights (although they aren't hanging in the ghost version).

I've tried these types of shots with and without a filter - and while without a filter usually is better, it does not eliminate the problem.

Any thoughts on what this is, why it's caused?

Thanks in advance for your thoughts!

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Lens flare - essentially internal reflections and very difficult to cope with when thelight source is in the frame.

Ya, you have too much direct light coming straight into the lens. A filter would add an extra layer of glass for the light to bounce around off of, and increase this effect.

On the whole having direct light shine straight into the lens is a bad idea, except perhaps in certain situations where flare can be a creative effect. Like all these effects, it can also be over used - like the nausea -inducing blurred waterfalls and the stroke-inducing blood red film of a 'sunset filter'

With digitial cameras the sensor itself has a reflective surface, and it can sometimes 'see' it's own reflection off of a layer of glass within the lens - this is 'ghosting' . The sensors and also lens elements have coatings to help with this - your lens is I presume one of Sigma's DG lenses ( digital glass) which is optimised for digital cameras with such coatings.

Practice with the lens, discover how it performes in certain circumstances, and avoid or use those circumstances as you see fit. But above all, enjoy.

Was there a pool (out of site) in this picture?

Also the sigma lens hood leaves much to be desired.

Thanks to all for the responses.

Yes in fact there were two bodies of water beneath the picure - a pool to the right of the roof of the smaller building pictured, and a small lake to the left of the roof of the building pictured. Am I correct in assuming the reflected light off the water would cause additional problems?