Bart van der Wolf wrote:
"frederic pichon" wrote in message
my soft to make Panoramas (photostich) often ends up doing them on a curve. How can I straighten up the picture, ie decurve an image?
First you’ll need to start with using a leveled tripod when shooting. Next you could use a different stitching utility, allowing to control yaw, pitch, and roll. The pitch and roll parameters can be used to distribute the tripod leveling errors evenly over the composite image.
Bart
It is often more than that. A curved pano is due to the camera being pointed slightly up or down during taking. It is almost impossible to keep it level by hand. You are right that a leveled tripod will fix that.
I have a big, heavy pano head on a great tripod that will do that just fine. However, it’s all rather big and heavy. So, I find that I rarely take it with me.
Luckily my Hugin frontend to Panotools will stitch it very nicely. However, it takes more that control points for the yaw, pitch, and roll to correct a curved horizon.
I have found that the best and easiest way to correct the curve of the horizon in Hugin is to have an object on each end of the pano that is vertical. Horizontal will work too. You then put in a "vertical line" set of control points. Do this for one frame on each end, giving you two vertical lines. Hugin/PT will straighten everything up just fine.
Of course, you don’t always have anything straight in a pano. Landscapes are particularly bad for having nothing to line up to. I have tried to skew bits of the picture at a time in Photoshop, but it’s a pain. It hasn’t been very satisfactory either.
I usually stitch the pano and leave the curve in. Then Enblend. Then I open the pano in Hugin as one image. I then apply an artificial horizon using the same control point method as above. The difference is to make one horizontal line from the center to the right side and another from the center to the left side. You are likely to have to do it over several times until you get it looking right.
None of these techniques work very well for 360 degree panos. I have found that handheld 360 panos are almost impossible to get straight and not wavy. The pano head on a tripod will be what you want for 360.
Clyde