#1. "RE: Strange edges on HDR merges" In response to Reply # 0 Wed 16-May-12 07:04 AM by Antero52
Different alignment across the component shots perhaps? Even if you use a tripod, if you have VR on, you'll have slightly misaligned captures. HDR software can re-align the content but some of the edges will be present in only some of the component shots. If you mean "top or bottom" (not both) literally, misalignment in the vertical direction may be the culprit. If the problem was with the D800 sensor, you'd see artefacts at any high-contrast lines, not just the picture edges. Your VR may be in the "active" mode wherein vibration in the horizontal direction is not compensated, to provide faster horizontal panning.
#2. "RE: Strange edges on HDR merges" In response to Reply # 1
The thin bright line was always on either the top or bottom...not both at the same time. Now that I think about it, I can see that it is the vertical misalignment. With Photomatix merge, you can elect to crop the misalignment off during the merge. CS6 does not have that option; you get the entire 32-bit merged file to deal with after merge.
I think I prefer the manual crop. Seeing the thin line tells me I am still not totally stable with my tripod/mount combo.
With the D300, I could get away with "not totally stable." I guess with the D800 I have to redefine stable when shooting the HDR frames.