Template Stitching

Discussion forum for techniques and issues relating to the creation of panoramic and/or "mosaic" images

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luigi
Posts: 21
Joined: Mon Apr 06, 2009 6:34 pm

Template Stitching

Post by luigi » Wed Feb 09, 2011 1:07 pm

Hi All,

Sorry if this is not the correct name for the technique. If it has been discussed previously please kindly point me to the thread.

If I have a good rotator is there a way to sticth without using control points by just saying the # of degrees between shots ?
I'm asking this because for night panoramas of the sky I'm using a rotator because it makes the capture of the images easier. Then I'm wondering if I can take advantage of the rotator to do a simple stitch based on that.

Thanks!
Luis

waters
Posts: 96
Joined: Mon Dec 26, 2005 10:38 am

Re: Template Stitching

Post by waters » Wed Feb 09, 2011 4:47 pm

In PtGui it is suggested that you do a good stitch in daylight and get your average CP distance as small as possible. Save this as a template and you may have good luck stitching a night scene. Fortunately there should be much less parallax error in a panorama of the sky.

luigi
Posts: 21
Joined: Mon Apr 06, 2009 6:34 pm

Re: Template Stitching

Post by luigi » Wed Feb 09, 2011 7:58 pm

waters wrote:In PtGui it is suggested that you do a good stitch in daylight and get your average CP distance as small as possible. Save this as a template and you may have good luck stitching a night scene. Fortunately there should be much less parallax error in a panorama of the sky.
Thanks!
Is the distance to the subject relevant?

waters
Posts: 96
Joined: Mon Dec 26, 2005 10:38 am

Re: Template Stitching

Post by waters » Wed Feb 09, 2011 8:25 pm

Luigi:

You may want to read up on parallax error, but if you are shooting the night sky in an open field, for example, there would be little to worry about. In a smaller space with objects in the foreground, it becomes very important, as there is only so much magic a stitching program can conjure. Line up two fingers in front of your eyes and turn your head. The fingers don't stay lined up, but on a camera lens you can adjust the point of rotation ( referred to variously as the Nodal Point, etc. ) such that near and far objects stay aligned through the swing of the lens. Eliminate near objects and you nearly eliminate the problem. John Houghton has a great tutorial on establishing the Nodal Point.
After looking at your reply again I understand your question about distance to subject. I think if you establish your template in a decent sized room the parameters should translate for far objects as well. The establishment of a good Nodal point for your lens is important because it makes the work of the stitcher easier ( or even possible ) Careful calibration yields better results down the road. John's tutorial involves a close object such as dark tape on a window and a far object, the farther the better.

luigi
Posts: 21
Joined: Mon Apr 06, 2009 6:34 pm

Re: Template Stitching

Post by luigi » Wed Feb 09, 2011 9:00 pm

waters wrote:Luigi:

You may want to read up on parallax error, but if you are shooting the night sky in an open field, for example, there would be little to worry about. In a smaller space with objects in the foreground, it becomes very important, as there is only so much magic a stitching program can conjure. Line up two fingers in front of your eyes and turn your head. The fingers don't stay lined up, but on a camera lens you can adjust the point of rotation ( referred to variously as the Nodal Point, etc. ) such that near and far objects stay aligned through the swing of the lens. Eliminate near objects and you nearly eliminate the problem. John Houghton has a great tutorial on establishing the Nodal Point.
After looking at your reply again I understand your question about distance to subject. I think if you establish your template in a decent sized room the parameters should translate for far objects as well. The establishment of a good Nodal point for your lens is important because it makes the work of the stitcher easier ( or even possible ) Careful calibration yields better results down the road. John's tutorial involves a close object such as dark tape on a window and a far object, the farther the better.
Ty you understood my question. Parallax is usually not important with an open sky and a telephoto lens. I wanted to know if taking a template inside my house would then be good to stitch a panorama taken at infinite (relative) distance.

Let's say I take a 5 photos pano inside my home and stitch them to minimal CP distance, save as template. Then I can take a night pano with the same setup and same 5 shots and it will stitch perfectly? Am I right?

johnh
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Re: Template Stitching

Post by johnh » Sun Feb 13, 2011 4:02 am

If you set up your panohead accurately, you can make a template inside your home, though you may need to create features with sticky tape for control points on blank walls and ceiling in order to get an adequate spread of control points. Ideally, you should use the lens at its same settings as you will use outdoors. This might well be a problem with a telephoto lens. It's easier to use a larger venue for the shoot - such as a large hall or church. Parallax issues are then a much smaller risk. However, if your main aim is to stitch photos of the night sky using the template without control points, you will have problems with the movement of the sky between shots. Long exposures are needed, and the sky will shift round significantly during the shooting of all the images. So you would still need a few control points to align the images perfectly. Of course, parallax effects are nonexistent for the sky and you could just make your template using shots of the night sky.

John

elf
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Re: Template Stitching

Post by elf » Tue Feb 15, 2011 12:57 am

It also depends on the level of accuracy you can achieve with your pano head. I'd try shooting a pano outside during the day using similar settings to what you'll use at night. Then rotate the entire rig 90 degrees and shoot another pano using the same settings as the first. Back at the computer stitch the first image, then use that as a template to stitch the second.

I don't know if PtGui outputs the settings like PTAssembler, if it does, then you can use those to verify the accuracy of your rotations.

luigi
Posts: 21
Joined: Mon Apr 06, 2009 6:34 pm

Re: Template Stitching

Post by luigi » Tue Feb 15, 2011 2:54 pm

elf wrote:It also depends on the level of accuracy you can achieve with your pano head. I'd try shooting a pano outside during the day using similar settings to what you'll use at night. Then rotate the entire rig 90 degrees and shoot another pano using the same settings as the first. Back at the computer stitch the first image, then use that as a template to stitch the second.

I don't know if PtGui outputs the settings like PTAssembler, if it does, then you can use those to verify the accuracy of your rotations.
Ty! If the head is properly leveled I think I can use the Yaw values to control if they are the same for all frames, roll & pitch should be near 0.
I have to make a few tests, for some reason the softwares have trouble aligning stars or night shots, I can always place control points on the stars manually and it works nicely but it takes time.

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