natural lens flare on coldish but sunny alley

Flare can take many forms, and this may include just one or all of the polygonal shapes, bright streaks, or overall washed out look (veiling flare) shown above.
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Flare
Techniques Glossary Flare
Flare is unwanted light reflecting within a lens or camera that reduces contrast and creates bright streaks or patterns on the image.
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Flare and ghosting are a major problem in contra-light situations. The problem is caused by reflected light - either from the lens elements or the inside of the lens barrel. There are certain techniques to reduce these reflections: ...
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Flare:
Cause: It is light reflecting off the inner and outer surface of a lens. Solution: Use a lens hood. Remove UV Or Sky light filters.
Dark corners in the picture: ...
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Lens flares are currently a visual cliche and are often added to images digitally. When you don't want lens flares, use a sunshade on your lens and watch out for light sources in your camera's field of view.