Can telephoto lenses cause the background to be darker than the foreground in the same light?

Question

I took this photograph yesterday afternoon at around 5:15pm EDT, about two hours before sunset:

The sky, in my perception, was bright, and my little subject is standing in the same lighting as the bushes behind her. She's well-exposed, but the sky and background foliage appear darkened — even though they were most definitely not in the shade. To my eye, everything was bright, and while I'm not unhappy with the contrast in the final result, it seems a bit strange.

This is a linear histogram of just the foreground subject (selected by hand):

and here's the same for the background:

and for completeness, the full-image histogram:

Here's an iPhone snap taken a few minutes later; she's in the shade in this, but when the above picture was taken, she was in the bright sun by the shrubs you can see in the center background, as are the shrubs themselves.

That's far from a technically-great image by any measure, but you can see the brightness of the sunny areas.

Here's the key EXIF from the image:

Date                            : 2012:03:23
Time                            : 16:12:54
Camera Model Name               : PENTAX K-7
Lens Type                       : smc PENTAX-DA* 200mm F2.8 ED [IF] SDM
Focal Length                    : 200.0 mm (35 mm equivalent: 300.0 mm)
Flash                           : Off
AF Point Selected               : Center
Metering Mode                   : Multi-segment
Effective LV                    : 13.5
Exposure Compensation           : 0
ISO                             : 160
Aperture                        : f/4.0
Shutter Speed                   : 1/1000

What's going on here? Is this somehow an effect of the 200mm focal length I used? And if so, how could that be? (I wouldn't think this to be the case, except it's not something I've really noticed with my more-typically-used shorter lenses, even in similar outdoor situations.) Or is it simply a matter of the difference in tones and reflectivity of her bright clothes and light skin as compared to the green bushes? Are my eye and brain compensating for the dynamic range such that my judgment of the scene doesn't match reality? That seems plausible, but the sky was definitely bright — we've been having uncharacteristically lovely spring weather in Boston — and it appears rather dim in the photo.

Asked by mattdm

Answer

I don't think that focal range has anything to do with it.

I think that the issue is that different materials reflect light differently. Althought the different elements of the picture are illuminated by a uniform light source, they do not reflect the light equally. The green foliage is normally about 2/3 stops darker than neutral (18%) grey. The white part of the dress is of course much brighter than neutral grey. The colors in the dress look very vibrant, so I would suspect that would also reflect more light than neutral grey. And she does look like she has bright skin, so I would think that she would also reflect more light than neutral grey.

So I think that the darkness of the background is simply due to the fact that it reflects significantly less light than your main subject that the exposure has been metered for.

When you are physically present at the scene, your brain makes up for this, and what you perceive is that they are of equivalent brightness. But when you take a photograph and look at the photograph, it will reveal the difference in light reflection.

Answered by Pete

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