20mmf1.7 : Strange artefacts in the night sky

[Jim-st]

I took a series of pictures beside the river clyde in Glasgow the other evening using the GF1 and Panasonic 20mm f1.7.
In a few shots I got weird "lights" in the dark sky, presumably some sort of flare. The following shots were all taken wide-open at ISO 1000, 1/20sec

First shot is flare-free:

Second shot has some flare points:

Third has same flares as previous, plus a couple more:

Layering second and third in Photoshop demonstrates exact co-incidence of the spots common to shots two and three:

These spots are pretty lethal, like big fried egg shapes and not easy to get rid of in PP

Has anyone else seen this sort of thing with the 20mm f1.7?

Can anyone suggest what's causing this, bearing in mind it's intermittency (about 6 shots out of 30 that evening have these artefacts)?

Might it stem from having a UV filter mounted on the lens?

Any suggestions??

Thanks in advance

 

[greyelm]

Although I haven't had artefacts like yours I did get flare from a UV filter on my 20/1.7, enough that I have now taken it off. All I can suggest is trying some test shots with and without the filter.

 

[Jim-st]

Although I haven't had artefacts like yours I did get flare from a UV filter on my 20/1.7, enough that I have now taken it off. All I can suggest is trying some test shots with and without the filter.

Thanks, greyelm - the filter does seem the most likely culprit. Hard to do any sort of controlled test for anything so intermittent, so I'll maybe just avoid using a filter after dark. Then if the artefacts don't return I'll know why!

 

[boomguy57]

I would also say it's the filter.

 

[Charlie Lemay]

I've kept a UV or ND B+W MRC filter on my 20mm f1,7 since I bought it and never noticed anything likke this The tiny white circles do seem like a reflection because they are in the same configuration as the larger lights which actually appear to be street lights. If you enlarge the image on screen even at this low resolution, you can see that each of the large orbs of light are next to a vertical pole and there is an arm going from the pole to the light. They never change position in relation to the poles. The small reflected artifacts should be easy to fix. The larger ones look like they are actually lights that are there to me.