View Full Version : Need help stitching grey sky
10-02-2013, 11:04 AM
I have a 360 pano which was taken on a day with grey sky, and my eye (as well as Hugin) cannot find any place from which to make control points. I tried selecting random places as control points, hoping to fool the program, but Hugin is smarter than that and it did not work.
Does anyone have any suggestions on how to add the "up" shot which is grey sky?
OR, with a 5D MkIII and a 16-35 lens set on 16mm, is 30 degrees pointed up (with a NN5L) enough to not need the "up" shot? If so, will the pano be less than 180 degrees top to bottom?
10-02-2013, 11:58 AM
you could use the "Align to grid" function. You can find it under >Project in top tab. It adds pics in a row one after the other to stitch them one by one for the blue sky for example. It should work for a grey sky as well I suppose.
10-02-2013, 08:25 PM
In PTGUI, you can drag the image in place. You can also guess the yaw,pitch,roll values and input them in the image parameter. You just don't optimize the image of sky for control points.
10-02-2013, 11:53 PM
With the 16mm lens and two rows at +/-30°, the panorama will cover a vertical fov of 153°, leaving a 27° diameter hole at the zenith (and nadir) to be filled.
A useful resource for recommended shooting configurations can be found at http://www.vrwave.com/panoramic-lens-database/.
Adding the grey sky zenith should be easy if you think back to when you shot the panorama. You will have swung the camera up to +90° either from the first or last shot of the row previously shot. So it will have the same yaw and roll parameters of that previous shot and the pitch is +90°, so the three parameters can be directly entered on the Images tab of Hugin to position the image accurately. Do this after levelling the panorama. In this state, the pitch parameters of all the images in a row will then be the same (theoretically). One thing to beware of is the possibility of the zenith image being upside down. With the camera pointing directly upwards, the orientation sensor will not deliver sensible data as gravity is acting at right angles to the plane of the image sensor. So it's best to switch the camera's auto rotate feature off to make sure all the images are in the same orientation. In any case, you can easily try rotating the zenith image by 180° to see which position blends in best.
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