[blende8]

The moon moves in about two minutes through his own diameter.
This is too slow to result in the enlongation shown.

[pingflood]

I still think I'm right.

I've seen instances where SR doesn't kick in immediately, and that could well cause this exact thing.

[WerTicus]

the moon moves pretty quickly

[pingflood]

No it doesn't... especially not at those focal lengths.

[KungPOW]

Was there a UV filter on the lense? I'm just throwing this out there. Typically a filter reflection would show as a green ghost mirrored to a bright object across the vertical and transvers axis. So in this case I would expect to see a ghost in the bottom right corner, but there isn't one. I expect you didn't have a filter on the lens, but I am just asking.

I think the colour shift arround the moon is due to a combination of chromatic aberation (ie purple fringe) plus over exposure. If the red chanel burns out before the blue does, the result is a blue fring instead of a purple fringe. The opposite side shows the greenish colour that is often seen along with purple fringing. This makes me think that the elongation of the moon is a result of the CA near the moon itself has been over exposed to the point where it pure white, and as a result it looks like the moon is oval.

So in short, my therory on you oval moon is that it is a result of extreme overexposure combined with CA from the lens.

[snostorm]

I'm with pingflood on this one. Camera shake is going to be much more evident on the overexposed bright object.

Scott

[khardur]

I agree with the "this is an aberration" camp here, not related to SR at all.

I have a few pictures where I have seen a similar effect. Slap your camera on a tripod, turn SR off, put a streetlight in a similar position at the edge of the frame and take a picture with the same settings. I would almost bet my paycheck you get the same result.

[Ex Finn.]

I go along with the aberration or maybe even internal reflection theory, coupled with overexposure.

Cheers, Mike.

[KungPOW]

This question needs a poll!

[ma318]

I would go with the CA theory. The exposure time was 1/10 sec so it could not be due to moon movement.

Light reflected to the Earth from the Moon's surface is composed of colors throughout the visible spectrum. So moonlight, like sunlight, is more susceptible to CA versus the reflected light from the building.

Using a wide angle lens with the subject, reflecting a full color spectrum, near the edge is also more susceptible to CA versus using a telephoto lens with subject, reflecting a full color spectrum, in the center.

[RobG]

Thanks for all the responses - I had no idea it would generate so much discussion! Someone asked for a poll - but that would require knowing all the possible answers. From all that I've read, my own opinion is that it is a side effect of stabilisation in that (as some have suggested) the comparatively bright moon is much more likely to show movement than the dim building. While the fringing may well be connected with lens abberation, I don't think the elongation of the moon itself is.

However, someone mentioned internal reflections within the lens, and I have had issues with this in the past but with a longer lens. It's possible because the lens is shot, the reflected image of the moon is close to the real moon, blurred together over the length of the exposure.

If anyone has the opportunity to do a test with and without SR, I'd be interested to see the results.

[pingflood]

If somebody does decide to do a test, I think three types of shots should be tested, probably with a half dozen of each type:

1) On tripod, no SR

2) Hand held, SR on, no half-press and wait for SR to kick in

3) Hand held, SR on, half press and wait for SR to kick in

I am guessing that #2 will yield similar results. I don't agree with the lens abherration theory unless you had a coke bottle mounted on the camera.

[RobG]

If somebody does decide to do a test (snip)
2) Hand held, SR on, no half-press and wait for SR to kick in

Meaning effectively no SR?

3) Hand held, SR on, half press and wait for SR to kick in

Since this option is with SR

I am guessing that #2 will yield similar results. I don't agree with the lens abherration theory unless you had a coke bottle mounted on the camera.

As I have said, it was the.... oops. The EXIF data said f2.8 so that means it had to be the 35mm f2.8 limited NOT the 16-45. Sorry! I assumed it was the zoom, but it must have been the first time I used the new lens! Anyone still insisting on aberrations?

Anyone still insisting on aberrations?

I still say it's not SR and it's probably not aberration, just an optical quirk caused by exposure, distance to subject and the length of time the shutter was open.

[Adam]

The moon "moves".

This is in fact the true reason AFAIK; any shutter speed below ~1/125s for moon shots will show slight signs of motion blur.

The elongation in your photo looks like it's more due to exposure or CA, though.