Thanks Bart. I think a level other than my tripod one is the way to go. I do think Im getting level or very close but there seems to be some distortion. Both of these images had a lot of shift but no tilt and there seems to be some barrelling. This is with the 24mm without the converter. I know its onlyslight but would this be expected with the lens. I guess i can correct in PS or LR.
Hi,
The tripod levels are not all that accurate, but it will remain difficult to nail the leveling in-camera as well. For very accurate work I tend to square the image in a Pano stitcher such as PTGUI or Hugin.
Judging from the images, there is no
geometric lens distortion to speak of. Maybe some can be detected at full size, but still negligible. There is a minor amount of Yaw, Pitch, and Roll, as detected by PTGUI, and corrected in the attached image which is now virtually perfect.
For example, the
projection distortion for P1 was caused by:
Yaw: -0.0115 degrees
Pitch: 1.9962 degrees
Roll: -0.3315 degrees
and for P2:
Yaw: -1.4425 degrees
Pitch: -0.9158 degrees
Roll: -0.0967 degrees
As you can see, also very small corrections, hardly possible to detect when composing the shot in camera, but still noticeable on wide angle shots.
In addition, one may want to
not correct the Pitch angle for 100%, because it might look a bit more natural to leave some keystoning in the image. Changing the Pitch angle a very small amount in the Stitcher settings is all that's needed to achieve that more natural look. Lightroom and Photoshop ACR make somewhat similar (faster but a bit lower quality) choices for correction with the Upright feature, and also allows subsequent manual tweaking of the vertical correction to deliberately under-correct keystoning.
Another consideration is that buildings are not always perfectly square and, like these examples, may feature façade elements that are less or more recessed which can cause an optical illusion of distortion where none is in actuality.
Cheers,
Bart
