Any pixel transformation is going to reduce the sharpness to a degree and if you are starting with an area just on the limit then it could quickly stray into the unacceptable.
This discussion summarises some of the issues. Unsurprisingly it comes out strongly in favour of T&S lenses as it is by Rodenstock but it does show the issues well.
Thanks a lot for that excellent article from Rodenstock, its heavy reading but I am sure
it will answer my question.
Obvious point, perhaps - but instead of expanding the top, shrink the bottom. Yes, you lose total resolution, but with the newer high resolution sensors that shouldn't be a big problem. And the end result may still look better.
If you need very high resolution, there's always stitching. Same principle: reduce the base image a bit before running the align, so that you avoid too much stretching in the edge frames.
It seems like there are limited answers to the pronlem.
1- buy shift lenses, very expensive but if its necessay, then it has to be, I am not sure how Canons 17 and 24mm
lenses will preform, any experience here?
2-Double up my sensor size and leave ample space in order to pull in the bottoms of the image.
3- Even more expensive, go for larger format with shift facilities.
Can you successfully stitch vertical images that have not been shot on a shift lens? any tips?
1 person found this helpful
Can you successfully stitch vertical images that have not been shot on a shift lens?
In principle there's no problem. Take one horizontal base shot with no perspective distortion, and put that at the bottom of the stack. The others, that do have perspective distortion, will be automatically corrected to that.
If you then scale down this base shot first, there won't be stretching at the top. All resampling is down, not up.
However, for optimal results you need to avoid parallax error. That means the camera must be rotated around the optical center of the lens (that's where the diaphragm appears to be when you look into the lens from the front). This is easy enough horizontally with a focusing rail, a bit more tricky vertically. I raise and lower the center column by a predetermined amount, marked on the column.
Turn on lens correction in ACR! You need good rectilinear correction before merging.
Oh, one more thing. Don't use Photomerge. Run Auto-align first, then Auto-blend. Once the frames are aligned, you may need to nudge layers a couple of pixels. Sometimes Auto-align offsets individual layers a bit, I don't know why. Go to 100% and check for perfect alignment.