John Hudson wrote:
> Hi Moose ........ I was thinking. What made you think that the pole was shown
> to be leaning other than through barrel distortion.
Simple enough. It appeared to be leaning toward the center - to roughly
the extent I might expect in a relatively wide angle shot looking up
slightly from the horizontal. I seem to have a fairly acute sense of
level. I used to drive a tech photographer who worked for me crazy. I'd
walk into the camera room and remark that the subject was mounted not
quite level. He's grab his leveling device, find I was right, often by
1/2 deg. or less, and shake his head.
I wasn't sure, as the curve looked as though it might be an actual bend
where the two parts meet, but it also looked like there might be barrel
distortion.
To satisfy my curiousity, I looked at it with a grid and found it was
both leaning and bowed/bent. I didn't know if one or both were a result
of photographic aberrations, or actual qualities of the subject.
Hence my question.
> Hopefully my 12-60 is not a barrel distortion lens. The 14-45 kit lens was
> horrible for barrel distortion.
>
It does have noticeable barrel distortion, worst at 12 mm and almost
gone by 18 mm. As Mike says, PTLens will quickly and easily correct it.
What he didn't mention is how useful PTLens is as a way of seeing the
distortion in lenses on doesn't have at hand. Simply load an undistorted
image with some horizontal and vertical lines, turn off auto EXIF
recognition, manually select the lens in question and observe the effect
of clicking Preview on and off at various focal lengths.
Now that I know what lens was used, I checked the image and found that
the bowing in the pole is slightly greater than that caused by the 12-60
at its worst, 12 mm. So it appears the pole may actually be bent.
> Would you have come to the same conclusion had the shot been, say, of the
> Leaning Tower of Pisa.
>
Probably not, even if I didn't know about it. For one, it isn't
noticeably bowed. Second, there are other nearby structures that would
provide a reference. Even relative to the level ground around it, the
angle is obvious. (No, I haven't been there, but I did watch a special
on PBS about efforts to stabilize it. :-) )In more natural
surroundings, on un-level ground and with no points of reference (even
the horizon is hills that clearly aren't level), the Stanage Pole is
trickier to be sure about.
> Now there is a challenge.
>
> How about finding a shot of the leaning tower and making it stand up straight
> and thus gain fame beyond that of Leonardo of Pisa :-)
>
Relatively easy to do, but I doubt that PS manipulation of such things
is a way to fame and fortune. :-)
Moose
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