-- thanks for sharing the full details!
You want the full details? Okay! I'm in strict scientific mode for this post; no arty farty pretensions.
There's no doubt that the above 3 images were taken in progressive sequence, from left to right. The metadata indicates there are just a few seconds between each shot. However, looking at the larger sequence of shots on each side of these 3 (I took a few dozen or so from this position with various lenses), it's now clear that the first image is the third of a previous group, panning from right
to left, not the first of a second group panning from left
to right. I took over 12,000 images on this trip and have difficulty sometimes in remembering the precise circumstances of each shot. However, having given it some thought, I can now reconstruct the exact circumstances.
These particular images were taken with the 5D on a Manfrotto 740SH tripod from the top of a 'look out' tower. It's a rather inadequate tripod for stitching purposes, being a ball-head, and doesn't have much height, even with the column fully extended. But it's very light and compact and serves its purpose for stitching with a T&S lens using the RRS L bracket and clamp.
The 'look out' tower of course has a fence around the platform to prevent people falling off. My tripod was not high enough to allow the lens an unobstructed view over the top of the fence. My guide, a very obliging chap, suggested he might be able to find a few slabs of rock to elevate the tripod. So whilst my guide was searching below for suitable slabs of rock, I was taking handheld shots, some for stitching and some not.
A few minutes later the guide appeared carrying a few rocks that did the trick. I normally pan from left to right because Panavue IA positions images in numerical sequence. But on this occasion, lens flare from the sun on the right was a problem, so I started from the right, then back from left to right, then back from right to left and so on. Here are the first 5 shots.
[attachment=2044:attachment] [attachment=2045:attachment] [attachment=2046:attachment] [attachment=2047:attachment] [attachment=2048:attachment]
As you can see, the first image is reasonably level, judging by the clouds. The second image is not too bad but has a more noticeable slope to the left and the 3rd image is just atrocious. To what extent this is due to the ball-head and to what extent due to the effects of a wide-angle lens tilted down, I'm not sure. But it's clear that between the third and fourth shot, I tried to correct the tilt but overcorrected so the horizon is now sloping the other way slightly. However, in the 5th shot, the clouds are sloping in the opposite direction to the 4th shot, which tends to indicate the ball-head is not keeping the camera level.
Now, as you know, a good tradesman always blames his tools when things go wrong, so I'm blaming that ball-head tripod.
I converted the first 3 images again, paying particular attention to keeping the vignetting amount, vignetting mid-point, temperature and tint the same for each shot, something I sometimes overlook. Keeping the conversion settings identical in every respect seems to improve the tonal transitions between images in the sky. The image below shows how CS3 auto stitch compares to the best I can do with Panavue's Image Assembler using flags and lens selection, and also Panavue in full auto mode.
It's interesting to note that the CS3 result is significantly smaller in spite of more white background. The Panavue result in auto mode has duplicated the person being photographed in the foreground, otherwise it seems okay. The 'flag' stitch has a slight discontinuity near the base, as shown in the interpolated crops, and has used the duplicated figure in the middle image as opposed to CS3's preference for the first figure.
I should also mention that the first 3 images in this sequence were taken with the zoom lens set at 21mm. When I corrected the horizon level in the 4th image, I also changed the focal length to 25mm. The stitches in previous posts consist of one image at 21mm and two at 25mm.