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View Full Version : Questions from a Panoramic Dummy...



Arthur Morris
07-15-2008, 03:16 PM
This is a five frame pano created using Auto in Photomerge. The five images were created with the handheld 24-105 at 67 mm. The ORIGs were in HORZ format.

What did I do wrong? Does it have to do with the nodal point???

Why is the horizon curved?

Is there any way to change the perspective in PS so as not to lose so much of the frame, ie., to level the horoizon???

Get to work David!

Dan Brown
07-15-2008, 05:57 PM
Hi Art. Pretty scene! When you ran the photomerge automation, what did you select on the left? I think that if you select "reposition only" or "interactive layout" you will not get the curve, not sure though. Dan Brown

Brian Wong
07-15-2008, 10:03 PM
Hi Artie!

Really nice pretty sky, and I can see what you were trying for in composition. This has great potential!

The "nodal point" (point of no-parallax) setting probably has very little effect on this image. That setting usually comes into play when you have a very close object that is being merged between frames ... hence causing a parallax problem. With far off landscapes, you can be very loose with that setting and get by.

For the curved horizon ... this has more to do with the "projection" the software application is giving you. Most applications are expecting the photographer to be inputting "level" images. Your horizon is low on the panorama, so I suspect that you were aimed higher (into the clouds). You can see the effect if you produced another panorama, but with your central sensor right at the horizon. With your same application setting, that panorama would probably have a flat horizon. Finally, if you pointed slightly downward ... then with your same application settings, that panorama would probably have a horizon bowed upward (smiley face!!).

Various different applications have different ways to deal with these projection distortions. However, I have found that large panoramas usually end up loosing lots of the frame ... so allowing for a crop by taking extra images all around is a good strategy. You have also recognized the other strategy ... to try a vertical (portrait) format (to get more vertical in each frame).

There is a limit to all this, as panoramas are really representation of a sphere (where the photographer is the center of the sphere). As with viewing a globe of the Earth vs. a flat map of the Earth ... the North and South poles become distorted in the flat map (orange peel effect). The various projections offered by the applications are the different ways they are handling the distortions.

Hope that is helpful, and hope David and others can correct me if I am wrong!

Robert Amoruso
07-16-2008, 08:02 AM
Artie,

Dan's right on the Photomerge settings. Try reposition only and if that does not work, then interactive layout where you match up the images. Make use you have Blend Images Together (bottom of dialog box) checked. If you still get some curvature, use filter > distort > lens distortion to correct it.

Brian has a good explanation. IT is generally better for make the images taller then the scene you envision in the final product. I would also go one frame left and right to. At the distance you are shooting from, nodal point is not a big deal. I would do something like this handheld if the shutter speed was fast enough. As mentioned, keeping the horizon at the center of the image helps to control distortion - hence making the images taller then needed allows you to recompose later in PS to get the horizon out of the center. Anytime you aim a lens up or down, you introduce distortion.

Your other option is to use a TS (tilt-shift) lens. I have the Canon TS lenses and will use the shift feature to move the lens up or down with it level to the horizon to position the horizon as needed.

Going vertical allows you more room to create taller images to account for this and still get a high resolution.

Harold Davis
07-16-2008, 03:55 PM
i took the canon produced photo:D and took it into capture nx and did one of the things robert a talked about. just adjusted the distortion, leveled the horizon and cropped to rectangle. i think it looks pretty good. how bout you?:)

Robert Amoruso
07-16-2008, 07:49 PM
Nice work Harold.

David Kennedy
07-16-2008, 09:07 PM
A cylindrical projection, as opposed to the spherical projection displayed here, might alleviate some of the problems here, Artie. I haven't messed with CS3's photomerge enough to know if this is an option when stitching or not. (While I do like the new Photomerge, I've stuck with my favorite app, AutoPano Pro, for its ability to stitch images in batches.) However, Harold proves that there are still other ways to get around this problem.

Brian and Robert are correct that in this circumstance, rotating over the nodal point would not have made any difference. Only a close, foreground subject would betray problems of parallax so badly that they couldn't be fixed by some quick masking. That said, I still own and use all of the Really Right Stuff "nodal slides" (http://reallyrightstuff.com/pano/03.html) and other pano stuff. In the future, I would frame more loosely. Including more of the foreground in the images would have helped dramatically. 50mm might have felt too wide at the time you were creating the images for this pano, but once you put together six or eight 10MP files at 50mm, you can crop to your heart's content and still have an enormous file. :)

Arthur Morris
07-17-2008, 10:13 AM
Hi Art. Pretty scene! When you ran the photomerge automation, what did you select on the left? I think that if you select "reposition only" or "interactive layout" you will not get the curve, not sure though. Dan Brown

I used auto.

Arthur Morris
07-17-2008, 10:20 AM
Hi Artie!

Really nice pretty sky, and I can see what you were trying for in composition. This has great potential!

The "nodal point" (point of no-parallax) setting probably has very little effect on this image. That setting usually comes into play when you have a very close object that is being merged between frames ... hence causing a parallax problem. With far off landscapes, you can be very loose with that setting and get by.

For the curved horizon ... this has more to do with the "projection" the software application is giving you. Most applications are expecting the photographer to be inputting "level" images. Your horizon is low on the panorama, so I suspect that you were aimed higher (into the clouds). You can see the effect if you produced another panorama, but with your central sensor right at the horizon. With your same application setting, that panorama would probably have a flat horizon. Finally, if you pointed slightly downward ... then with your same application settings, that panorama would probably have a horizon bowed upward (smiley face!!).

Various different applications have different ways to deal with these projection distortions. However, I have found that large panoramas usually end up loosing lots of the frame ... so allowing for a crop by taking extra images all around is a good strategy. You have also recognized the other strategy ... to try a vertical (portrait) format (to get more vertical in each frame).

There is a limit to all this, as panoramas are really representation of a sphere (where the photographer is the center of the sphere). As with viewing a globe of the Earth vs. a flat map of the Earth ... the North and South poles become distorted in the flat map (orange peel effect). The various projections offered by the applications are the different ways they are handling the distortions.

Hope that is helpful, and hope David and others can correct me if I am wrong!

Brian, your explanations of the nodal point and its effect (or lack there-of) here and your expalantion of the cause of the curved horizon (I was pointing the camera up for more sky) were both excellent. Thank you.

Arthur Morris
07-17-2008, 10:30 AM
I am trying Robert's reposition suggestion right now and will let everyone know how that goes. In the meantime, here is the image that I created from the ORIG post with a rotation, a crop, and bit added center top and center bottom.

Brian Wong
07-17-2008, 11:08 AM
I am trying Robert's reposition suggestion right now and will let everyone know how that goes. In the meantime, here is the image that I created from the ORIG post with a rotation, a crop, and bit added center top and center bottom.

Hi Artie!

This is starting to look really nice! If your stitching application is unable to handle the projection distortion correction you are looking for ... I would try exploring a PS "Transform" from what you presently have (for the curve). Then just do a rotation to level the horizon. My guess is that this image is really going to sing!!!

Arthur Morris
07-17-2008, 12:28 PM
Robert Amoruso's suggestion to try checking "Repsosition" was brilliant. I created this repost after that great advise. Thanks Robert! (It needed 1 degree CW rotation but the horizon was pretty straight and I lost virtually nothing to Photomerge.

All comments on the image itself are now welcome.

Arthur Morris
07-17-2008, 12:38 PM
i took the canon produced photo:D and took it into capture nx and did one of the things robert a talked about. just adjusted the distortion, leveled the horizon and cropped to rectangle. i think it looks pretty good. how bout you?:)

Thanks Harold Well done. How do you "adjust distortion"???

PS: to David: thanks for your comments!

David Kennedy
07-17-2008, 02:14 PM
Robert Amoruso's suggestion to try checking "Repsosition" was brilliant. I created this repost after that great advise. Thanks Robert! (It needed 1 degree CW rotation but the horizon was pretty straight and I lost virtually nothing to Photomerge...

OK, that would suggest that this image needed to be treated more cylindrically than spherically--rather than bowing inwards, the files needed to stay pretty straight. Good to know you were able to do this without too much trouble in PS3. You might give AutoPano Pro a trial download at some point if you get even more serious about these...only thing is that its price tag is tied to the Euro. Ouch, I know!!!!!

I really am enjoying the colors in this image, in addition to your continued exploration of landscapes/scenics (whatever you like to call them). They can be a lot of fun!

Harold Davis
07-17-2008, 02:20 PM
Thanks Harold Well done. How do you "adjust distortion"???


i used the Correct......Distortion Control.....in Capture NX....a Nikon product. it's just a slider that lets you take out any amount of distortion. glad you like it!!

Bruce Murden
07-17-2008, 09:00 PM
Glad I waited for the reposts to see this. Final image is excellent, and our colleagues gave great advice for making panos for the first time. I think this is the right amount of the view to have, too. Any less would be unbalanced. Like repost in reply #10, where the purple-grey clouds at left side take you off the page. In the #12 repost, there's good balance with the island on the left, the clouds to its left, and the dark clouds on the UR. Keeps us bouncing back and forth. Good comp!