Help explain an optical effect

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The discussion centers on a photo of astronaut Tracy Caldwell-Dyson in the ISS cupola, where the distortion of the Earth/space boundary at the window edges raises questions about optical effects. Participants suggest that the observed distortion may be related to increased contrast at light-dark boundaries, potentially due to diffraction. The effect resembles capillary action but is likely symmetrical, with brightness differences influencing perception. One participant notes that similar effects can be observed by blocking part of one's vision with a finger. The conversation emphasizes a desire for a deeper understanding of the optical phenomenon.
Bandersnatch
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Hi, new to the forums, nice to meet you folks, etc.

Today the English wikipedia featured a picture of Tracy Caldwell-Dyson in the cupola of ISS(http://en.wikipedia.org/wiki/File:Tracy_Caldwell_Dyson_in_Cupola_ISS.jpg).
In that picture the arc of Earth/space boundary is visibly distorted at the window edges and where the astronaut's forearm obscures the view.
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Looks a bit like capillary action, although it's probably symmetrical and only appears to distort towards one side due to brightness difference around those points.

Anyway, last time I touched optics was in high school, and while I'd love to grok the how&why of the effect, I don't even know where to look for it. Is this due to diffraction? Something else?

It bothers me to no end, and I'd appreciate any help here, be it an in-depth explanation, or just pointing in the right direction.

Cheers chaps.
 
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It's in the camera - you are getting increased contrast at the light-dark boundary. Notice how the cloud detail is also washed out near dark foreground objects?
 
I don't know the reason. But if you just put your finger in front of one of your eye. You will see the similar effect.
Most likely it is diffraction effect. yes...
 
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