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Author Topic: image stitching  (Read 38505 times)
jnaneshwars
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« on: January 21, 2007, 07:29:52 PM »
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I tried to stitch four different images on photoshop 7.0. I followed the instructions given on the this site but the result shows the dividing line between images(attached). I must have gone wrong somewhere. Could anyone point out where it could be?
Thanks.[attachment=1589:attachment]
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feppe
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« Reply #1 on: January 21, 2007, 07:59:05 PM »
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I tried to stitch four different images on photoshop 7.0. I followed the instructions given on the this site but the result shows the dividing line between images(attached). I must have gone wrong somewhere. Could anyone point out where it could be?
Thanks.[attachment=1589:attachment]
[a href=\"index.php?act=findpost&pid=96903\"][{POST_SNAPBACK}][/a]

First of all, is there overlap between the shots? You need 20% or so overlap for the program to be able to look for similarities in the shots.

Second, PS's own stitching is crap (I heard CS3's is pretty good, haven't tried it though). Dedicated programs do a much better job, to the point of being practically impossible to tell after-the-fact that it's a stitched shot.

I've used Autopano which isn't free, but it's very good and easy to use. There are numerous other options, even free ones.
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BernardLanguillier
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« Reply #2 on: January 21, 2007, 08:01:36 PM »
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Your images show a very strong light fall off in the corners.

This is probably the result of a poor lens used at a less than optimum aprture and of some post processing. One first thing is that you should avoid to apply too much post-processing before doing the stitching.

A dedicated pano software like PTgui will automatically try to get rid of this light fall of to a certain extend.

If you prefer to stick to PS then you might want to try to reduce the light fall off (darken the center while lightening up the corners),

The best is course to re-shoot with your lens stopped down to the f stop that minimizes the light fall off.

Regards,
Bernard
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Wim van Velzen
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« Reply #3 on: January 22, 2007, 01:43:03 AM »
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CS3 (just beta now) is really a lot better in making panoramas dan CS2. In the few stitching I have been doing recently, it is as good or better than PTgui.
But even then, vignetting lenses can do a lot of harm.
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Kirk Gittings
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« Reply #4 on: January 22, 2007, 02:44:57 AM »
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CS3 (just beta now) is really a lot better in making panoramas dan CS2. In the few stitching I have been doing recently, it is as good or better than PTgui.
But even then, vignetting lenses can do a lot of harm.


I agree completely. The new CS3 is as good as anything out there. Having said that no program will make up for poorly shot segments. Quality stitching involves generous overlap, good non vignetting lenses (many of the tips mentioned above) and preferably a tripod mounted camera which pans around the nodal point and or a shift lens. Incredible images are possible if you are a careful worker.
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Ray
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« Reply #5 on: January 22, 2007, 05:41:03 AM »
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Quality stitching involves generous overlap......
[a href=\"index.php?act=findpost&pid=96949\"][{POST_SNAPBACK}][/a]

It's not always necessary to have a generous overlap with stitching programs like Panavue's Image assembler, Kirk. In fact too much overlap can be a bad thing, particularly if the shots are of a fairly close subject.  Even using the TS-E lenses where parallax errors are small, sometimes a perfect stitch can only be achieved by cropping the images, prior to stitching, to a bare minimum overlap... in my experience   .
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Kirk Gittings
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« Reply #6 on: January 22, 2007, 10:44:13 AM »
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Thanks Ray, That is actually part of my point. I just forgot to elaborate.
A generous overlap gives you many options to overcome possible issues in the final stitch.

For instance, my primary usage of stitching is to get a wider view than a 24mm (with DSLR, 47mm with 6x9 on film) when shooting interiors on commercial assignments. Usually all I do is a left then right shift with no pan at all. The overlap is huge (like 50%) and 95% of the time CS3 handles it perfectly, but about 5% of the time gets a bit confused with some funny things going on in the graded tones of the ceilings. Then I simply pre-crop the images with a smaller overlap at various locations to get a smother transition in the ceiling and it works out fine.
« Last Edit: January 22, 2007, 10:59:07 AM by Kirk Gittings » Logged

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RovingShoe
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« Reply #7 on: January 22, 2007, 01:17:23 PM »
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I tried to stitch four different images on photoshop 7.0. I followed the instructions given on the this site but the result shows the dividing line between images(attached). I must have gone wrong somewhere. Could anyone point out where it could be?
Thanks.[attachment=1589:attachment]
[{POST_SNAPBACK}][/a]

I use a freeware photo stitcher called Autostitch from the University of British Columbia.
It is truly amazing software.  I suggest you give this a try.

[a href=\"http://www.cs.ubc.ca/~mbrown/autostitch/autostitch.html]http://www.cs.ubc.ca/~mbrown/autostitch/autostitch.html[/url]
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jnaneshwars
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« Reply #8 on: January 22, 2007, 02:59:30 PM »
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I use a freeware photo stitcher called Autostitch from the University of British Columbia.
It is truly amazing software.  I suggest you give this a try.

http://www.cs.ubc.ca/~mbrown/autostitch/autostitch.html
[a href=\"index.php?act=findpost&pid=97023\"][{POST_SNAPBACK}][/a]

Thanks for all the various suggestions. I shot the image on an overcast day with a sigma 10-20mm wide angle lens. With a wide angle lens one could expect the image to be a bit dark at the edges than at the centre. Probably I may have gone wrong on masking in Photoshop.
I shall try AUTOSTITCH and check the results.
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BernardLanguillier
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« Reply #9 on: January 22, 2007, 04:33:35 PM »
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I use a freeware photo stitcher called Autostitch from the University of British Columbia.
It is truly amazing software.  I suggest you give this a try.

http://www.cs.ubc.ca/~mbrown/autostitch/autostitch.html
[a href=\"index.php?act=findpost&pid=97023\"][{POST_SNAPBACK}][/a]

Autostitch was the coolest thing when it was released thanks to its completely auto-stitching ability.

In the meantime commercial packages like Stitcher and PTgui have caught up and now also offer similar capabilities, but with a lot more manual control and better image quality (really seemless stitches, 16 bit support,...).

Regards,
Bernard
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Kirk Gittings
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« Reply #10 on: January 22, 2007, 04:44:25 PM »
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At this point in time, I don't find any of these stand alones to be any better than the new stitcher in Photoshop CS3. If you use PS and are going to upgrade anyway................
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Kirk

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jnaneshwars
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« Reply #11 on: January 23, 2007, 12:33:20 AM »
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At this point in time, I don't find any of these stand alones to be any better than the new stitcher in Photoshop CS3. If you use PS and are going to upgrade anyway................
[a href=\"index.php?act=findpost&pid=97063\"][{POST_SNAPBACK}][/a]


I tried stitching on AUTOSTITCH, which seems quite simple. Although my image has a cloudy background I have to try with images with more color contrast. Thanks for the numerous opinions which is appreciated.

Attached is the stitched image.
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ErikKaffehr
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« Reply #12 on: January 23, 2007, 01:00:16 AM »
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Hi!

I think that a larger overlap would help. Two suggestions I would make is to use a longer focal lenght and vertical camera position. I usually have something like 1/3 overlap.

The suggestions above should reduce the vignetting problem.

I mostly used "hugin" with "enblend" which is "opensource". Enblend handles small differences in densities between frames well.

Erik

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I tried to stitch four different images on photoshop 7.0. I followed the instructions given on the this site but the result shows the dividing line between images(attached). I must have gone wrong somewhere. Could anyone point out where it could be?
Thanks.[attachment=1589:attachment]
[a href=\"index.php?act=findpost&pid=96903\"][{POST_SNAPBACK}][/a]
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marcmccalmont
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« Reply #13 on: January 23, 2007, 05:50:28 PM »
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I've always had better luck stitching if I did the following to balance the images
1. DXO optics to correct lens distortion and vignetting
2. auto exposure ON
3. color match in PS prior to stitching
I hope this helps
Marc

[attachment=1615:attachment]
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Marc McCalmont
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« Reply #14 on: January 24, 2007, 02:06:16 PM »
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2. auto exposure ON

Auto exposure is a bad idea; your sample image still has some vertical luminance inconsistencies. You have some rectangular areas of sky noticeably darker than others just to the right of center of your image, although the edges are fairly fuzzy. It's better to shoot completely in manual mode, process the RAWs with identical settings, and correct vignetting as much as possible before attempting to stitch. Set your stitching program to output the final image in layers, so that you can manually control the final blend in PS with layer masking.

Here is a 3000x1000 pixel stitched image. See if you can find any seams, or guess how many frames went into the stitch.
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peterpix2005
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« Reply #15 on: January 24, 2007, 03:47:32 PM »
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FWIW, I  coluldn't get  a set of 9 images to stitch correctly with PS2, vbut the low end Stitcher program did it perfectly. Not sure how to attach a file  but I clicked the link below so hopefully it is there. A view from the Aburi Hills of reh plains behind Acrra, Ghana, an image from a book of Ghana photos I am publishing.[attachment=1621:attachment]
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peterpix2005
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« Reply #16 on: January 24, 2007, 03:58:50 PM »
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Sorry about the bad typing on the previous post. It is not my strong point!  BTW, that pan was made from hand held imges on Canon 5D with the Canon 24-105.

Peter
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plugsnpixels
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« Reply #17 on: January 24, 2007, 10:25:10 PM »
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On the Mac I've been using Calico. I still need to see how CS3 handles panos in comparison.
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marcmccalmont
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« Reply #18 on: January 25, 2007, 01:51:14 AM »
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Auto exposure is a bad idea; your sample image still has some vertical luminance inconsistencies. You have some rectangular areas of sky noticeably darker than others just to the right of center of your image, although the edges are fairly fuzzy. It's better to shoot completely in manual mode, process the RAWs with identical settings, and correct vignetting as much as possible before attempting to stitch. Set your stitching program to output the final image in layers, so that you can manually control the final blend in PS with layer masking.

Here is a 3000x1000 pixel stitched image. See if you can find any seams, or guess how many frames went into the stitch.
[a href=\"index.php?act=findpost&pid=97349\"][{POST_SNAPBACK}][/a]
Nice job, no I can't tell you stitched it. I'll try your technique next time
Marc
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BryanHansel
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« Reply #19 on: January 28, 2007, 02:37:16 PM »
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I've been using Hugins, which works pretty nicely for a free, as in free beer, program. Here's one that Hugins did on its own with very little help from me.
« Last Edit: January 28, 2007, 02:37:50 PM by BryanHansel » Logged

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