In an earlier post, I mentioned a spotlight which had caused flare within a photo. The frame is shown its entirety below to show the full nature of the effect.
You can see here how the bright blue light nearest the centre of the photo has been reflected within the lens, causing an area of reduced contrast with a blue colour cast on the side of the building (known as ‘ghosting’).
This is a common problem with zoom lenses when shooting in these conditions, although modern coatings do make the problem less significant. As you can see here, the Tamron 18-270mm has actually dealt with the flare quite well; the pattern caused is very simple, and easily remedied with a simple colour and contrast shift over the affected area.
Compare this with the complicated pattern in the shot below, from the Nikon 18-135mm:
As you can see, this problem will affect any lens under the right circumstances. You can limit this by using lens hoods wherever possible, or by composing very carefully so that bright lights are hidden within the shot. Incidentally, the only reason I didn’t do this in the shot above is that I only had a compact tripod with me at the time, meaning I couldn’t get the correct height to tuck the lights behind a handrail.
Some people choose to use multi-coat filters, but these can often increase the likelihood of flare by adding another piece of glass. As far as I can see, the Tamron shows only minimal ghosting – certainly better than my 18-135 used to – and I don’t feel it necessary to add such a filter, which would have a negative effect on resolution and sharpness.