What creates this strange flare and how to prevent it?

Question

I shot at a concert for the first time. The pictures were pretty good for the capability of my equipment, but on some shots, the light has a very strange flare. It isn't the usual rays, but some soft, non-symmetric form which I find quite strange, and, on most shots, distracting.

On this image, you can see it just above Gino's head and also behind his back, to the right of the mic stand. I am not sure if the slight blue lines on the left side of the picture (they form a triangle aimed at Chris's head, maybe not visible on all monitors) are part of the problem or if they come from a different light source.

What makes them appear, and how do I avoid them?

I shot with a D90 with a 18-200 lens, no filters or hoods attached. The settings were quite strained (iso 3200, often at max length and max aperture for the length. This specific picture is 1/125, f 5.3, 95 mm).

Answer 1

If you're talking about the strange arcs like in the bottom left corner of this picture:

Then it's just flare caused by shooting into a lightsource. Concert lights tend to produce strong flaring effects as they are very focussed.

The only fix is to use a different lens (they all flare differently) or not shoot directly into any lightsources. However when I'm shooting concerts I usually shoot directly into the lights on purpose and use any flare as an artistic tool to make the image more interesting.

Here's another image featuring some particularly strange flare from the Canon 50 f/1.8:

Answer 2

Your other choice is to use a hood. That will help avoid the flares from off the frame.

It also appears that the flare is accentuated by some CA as well. Stopping down a little or using a brighter lens that is better corrected may help.

Lastly, don't use UV filters indoors/at night unless they are multi-coated to remove such reflections. When in use, they provide two additional surfaces for flaring. It's better to leave them off in these situations.

Still, having flares used for dramatic/visual effect (eg: Star Trek) is in vogue. If you like this look, do all the reverse!