Circles of the Sun

Flare is an interesting photographic ingredient, and it’s especially prevalent in infrared photography. Whenever the sun is in the frame in an infrared photograph, you can be guaranteed some kind of flare! Sometimes you’d like to avoid it, other times it can be embraced, and in an image like this is almost becomes the subject itself.

Why do we have to deal with flare in infrared? Lenses have special coatings that prevent flare and other optical problems, and most of these are based on the principles of “thin film interference”. The same physics that puts rainbows in soap bubbles and creates colour in many of my snowflake images is used to cancel out flare, but there’s a problem. Thin film interference is inherently linked to certain wavelengths of light, thereby the lens coatings are only effective at certain wavelengths. Move to the infrared spectrum, and those coatings are either ineffective or counterproductive.

Infrared coatings do exist, but no standard photographic lens uses them. This means that flare in IR images is a visual ingredient that photographers need to contend with. You may choose to avoid it, though you might have fun embracing it from time to time. I’ve found that it can make for a very interesting element when used correctly.

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