Why do red subjects sometimes look unnatural in photos?
Asked 4/24/2011
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2 answers
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When I photograph strongly red subjects, especially when they fill most of the frame and there is very little background, the color often doesn’t match what I see in real life. Sometimes the red looks too saturated, other times slightly desaturated, with or without flash. I’ve mostly noticed this in natural light. Is this normal, and why does it happen?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
15y ago
2 Answers
18
It is difficult to answer the question accurately without knowing what you really photographed. But what you have reported is very similar to what many photographers experience when photographing red flowers.
This has a two fold cause.
First the CMOS sensor in the camera has an extended spectral response extending into the near infrared. See the diagram below. Taken from this Kodak publication.
A near infrared filter is normally fitted to limit the response to 700 nm, corresponding to the human eye. In practice the sensor is still responsive to some light in the near infrared range. See Thom Hogan, Shooting Infrared With Digital Cameras.
Secondly many red flowers have a strong spectral reflectivity extending into the near infrared. See the spectral response plot for the poppy below.(www.reflectance.co.uk, a database of flower reflectance) See also this paper, FReD: The Floral Reflectance Database.
It is the additive combination of strong reflectance extending into the near infrared and the slight sensitivity of the sensor to the near infrared that results in saturated, over exposed red flowers.
The way to deal with this problem is to spot meter on the brightly reflecting red object and treat it as if it were a highlight(which it is). Then increase your exposure by about 2 EV. The exact value will depend on the lighting and you will need to do some tests to determine the correction value.
Originally by user1368. Source · Licensed CC BY-SA 4.0
user1368
15y ago
0
Generated from our catalog & community — verify before relying on it.
Yes, this can be normal. Strong reds are a common problem in digital photography, especially with subjects like red flowers.
Two likely causes were noted:
-
Sensor response: Camera CMOS sensors can still respond a bit to near-infrared light even though they have IR-cut filters. Some strongly red subjects also reflect light into that near-infrared range, which can make reds record inaccurately compared with human vision.
-
White balance errors: If the red subject fills most of the frame, the camera may not have enough neutral tones to judge white balance correctly, which can shift color and make reds look too strong or too weak.
What to do:
- Use a grey card or set a custom white balance before shooting.
- Shoot RAW so you can correct white balance and color more accurately afterward.
- Be aware that highly saturated reds are among the hardest colors for cameras to reproduce exactly.
So yes, it’s a known issue, and red is one of the colors most likely to show it.
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