Summer Start

by VonSchnauzer

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

Super Anya

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):

subject histogram

and here's the same for the background:

background histogram

and for completeness, the full-image histogram:

full 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.

iPhone snap

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.

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2  
Regardless, think of it as bonus subject isolation! ;) –  rfusca Mar 24 '12 at 18:43

2 Answers 2

up vote 8 down vote accepted

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.

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What about the sky? –  mattdm Mar 25 '12 at 14:09
    
@mattdm: It can be the same deal with the sky. I shoot birds in flight a lot, and I try to meter off the bird. When the bird is well illuminated by the sun, the sky becomes a very dark blue. If I miss-meter, and meter off the sky, the bird usually blows highlights and the sky becomes a soft, light, baby blue. I think Pete has it nailed (and the blue sky is often a lot darker than you might assume...human eyesight has far greater DR than a camera, and the sky looks brighter to us than it does to a camera.) –  jrista Mar 25 '12 at 16:24

To add to what Pete said, not only do the leaves of the bushes have lower reflectivity, but on average some leaves will be facing the sun, some won't, and some will be shaded by others. Note that the sun is coming sideways to the picture. The girl's right side is much brighter as a result. Consider a good fraction of the leaves will be shaded by others and therefore more like behind a fold of the dress on her left side.

No, the focal length of the lens has nothing to do with this. On average, the brightness of the light from the bushes and the light from the dress, especially on the girl's right side, is very different for a combination of reasons.

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Would you expect a histogram of just the brighter leaves to be similar to the histogram of the girl, then? –  drewbenn Mar 25 '12 at 7:01
2  
@drewbenn: No, because as Pete pointed out the leaves have lower reflectivity than the very light dress, so will still be darker even when illuminated by full sun. –  Olin Lathrop Mar 25 '12 at 12:56

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