Re: Unexplained Alteration of Horizon

Michael Demyan <mdemyan@...>

Hi Dan:

I noticed the bow also. I attribute it to the spherical abberation of the camera lens.

I discovered that if in the Lens Corrections module the "Enable Profile Corrections" box is checked in the RAW converter (both ACR and Lightroom 3.6 allow for this adjustment) the images will have the anomaly.

The metadata on the RAW image shows the camera as Canon 5D MKII and the lens as EF70-200 f2.8L.

Mike Demyan

----- Original Message -----
From: Dan Margulis
To: colortheory@...
Sent: Tuesday, January 10, 2012 11:07 PM
Subject: [colortheory] Unexplained Alteration of Horizon

Can anyone explain an anomaly, apparently due to differences in acquisition, in the Grand Canyon images we're studying?

In all of the versions that I posted (which I derived from the raw) the far horizon is bowed, that is, the left and right sides are slightly lower than the center. The large majority of entrants have this characteristic and register with each other perfectly.

One entrant, however, submitted one where the horizon seemed to have been straightened, it no longer bowed but rather went very slightly downhill going from left to right. Although this image has the same number of pixels as all the others it doesn't quite register with them, especially higher up in the image, as the canyon itself is affected.

I thought that this must have been someone being hyperenergetic, but then two more entrants showed up with *exactly* the same pattern. The three entrants match up precisely with each other but not with the majority. So there has to be something funky going in in acquisition. Does anybody know what it is?

The three entrants who don't match the others are JJB, NJ, and JP.

Dan Margulis

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