Why do trees look reddish in a long-exposure moonlit night photo?

Asked 12/17/2013

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2 answers

I took a 63-second night exposure of a bright moonlit sky with a Nikon D60 and 18-55mm lens at 18mm, f/3.5, between 2 and 3 a.m. In the image, the leafless trees at the lower left look reddish-brown, even though in daylight they appear grey/silver.

There were no filters used. I wondered whether this could be infrared, moonlight, or possibly spill from a distant street light. What would cause this red tint in a long exposure, and is there a practical way to avoid or correct it in future shots?

color-cast lighting white-balance night-photography long-exposure

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

12y ago

2 Answers

Clearly there is some artificial light affecting the shot. Look at the top of the distant house too, and you'll see that it, also, has a red tint on the roof. And more importantly, there is a distinct shadow line on both the roof (from the roof next door) and on the trees (from the distant roof) that shows that the external source of light is coming in at a fairly low angle, probably just above the height of the house (but it's not easy to tell for sure).

Originally by user3558. Source · Licensed CC BY-SA 4.0

user3558

12y ago

AI Answer

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The most likely cause is artificial light contamination, not infrared. In the scene, other objects also show a similar warm/red tint, and the visible shadow lines suggest a low-angle external light source illuminating the trees and nearby roof.

A distant street light or other man-made light can strongly affect a 63-second exposure, even if it seems dim to your eyes. Long exposures let weak colored light build up, and pale grey/silver surfaces can easily pick up a reddish cast. Reflection from nearby surfaces, such as a red roof, may also contribute.

To reduce it in future:

change your shooting position or angle to avoid the stray light
shield the scene from nearby light sources where possible
correct the white balance or color cast in post-processing
if your camera allows, shoot RAW for easier color correction

A filter is usually not the best fix unless you know the exact light source spectrum. This looks more like mixed lighting than a camera IR issue.

Why do trees look reddish in a long-exposure moonlit night photo?

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