This is just a conjecture: I do not think this focused image of the
eclipsed sun is a pin-hole artifact. My guess is that it is a focused
image by the lens, but is a 2nd or 3rd internal lens relfection. In
this manner, the image might be reversed, and its brightness greatly
attenuated, so as to allow the sun appear to be displaced, properly
exposed, and in focus.
I don't see why the front surface of the lens would be hot. My guess
about the red glow is that it is a completely different internal
reflection, and that the circular nature of it is defined by the
circular edge of a lens component. I think this would be analogous to a
telescope's or binocular's "exit pupil".
-Bill
On 1/5/2011 2:54 AM, Frank King wrote:
Dear All,
A collegue pointed his iPhone at the
partially-eclipsed sun yesterday morning
and sent me the result:
http://www.cl.cam.ac.uk/users/fhk1/Eclipse11.jpg
It is clear that the camera wasn't stopped
down anything like enough but why, he asks,
does he get a pin-hole artifact of the
eclipsed sun?
At this stage of the eclipse the crescent
was the other way round from the way it
appears in the artifact. This is what one
would expect from an image created by a
pin-hole but not when printed and turned
the right way up!
Could this be an image of the reflection
in the water?
I know almost nothing about iPhone camera
technology and cannot give a convincing
explanation of the physics behind this
artifact.
There is also the surrounding elliptical
red background to explain. Could that be
an image of the hot front surface of the
lens?
Any thoughts?
Frank King
Cambridge, U.K.
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