June 30, 2005

Panoramic photos


This panorama (full resolution version) in my blog about the Gala Concert has caused a few people to ask about how it was produced. Basically it was put together from 7 or 8 individual shots, deliberately taken so that they overlap. I usually try to make the pictures overlap by at least 25% – up to a point, the more overlap the better.

Then I used autostitch to glue them together. Autostitch does what it says on the tin. Give it a collection of overlapping photos and it works out for itself which order they go in and how to paste them together. It doesn't do a perfect job. If you look at the top right of the Maths building, and especially the top right of Riley Court, you'll see some ghosting where the join isn't perfect (you'll need to look at the high resolution version to see this). But the end result is still pretty impressive for a fully automatic process, and touching up those imperfections is straightforward (so, why haven't I done it you ask:-)

I have another example produced with autostitch, taken of the National Mall in Washington DC from the tower at the top of the Old Post Office:

There's pano stitching functionality in Photoshop and Elements also. I haven't tried that yet. Does anybody know how good a job that does?

When setting out to deliberately take pictures for stiching together, there are some things to bear in mind:

  • Ideally you should pivot the camera around the optical centre of the lens. That's kind of hard to do, especially when you've got a zoom lens. The closest you can easily get is to use a tripod. As it happens, the Gala pano was not taken with the help of a tripod, so decent results are possible without. The Washington panorama was also taken hand-held.
  • Overlap the individual pieces by at least 25–30%.
  • If possible, use a manual exposure so that all the pieces of the pano have the same exposure.
  • If possible use manual focus to keep the focus consistent across the whole panorama.
  • Be careful of moving objects, or they might end up appearing more than once in the finished result!

When thinking about panoramas, I always used the think of mountains and open spaces as the major subjects, but this gala panorama has made me realise than the technique is more widely applicable. I'll be looking for other unusual opportunities to use it.

One thing I'd like to try sometime is to do a small scale version of the 2.5 Gigapixel photo, by stitching not just horizontally but also vertically, to create a very high resolution picture. I don't think I'll make 2GP, though! I just need to find a suitable subject…


- 13 comments by 4 or more people Not publicly viewable

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  1. My brother did an overlap photo once, but he just stuck some overlapping pictures on his wall. They were of a sunset, but came out a bit wierd as he was only using a disposable camera (he has a well posh camera now).

    30 Jun 2005, 19:10

  2. Paul Strapps

    I downloaded Autostitch last night and to test it's ability took 14 fairly random photo's of my car (I know, but it was just to test it out!).

    I made sure the photo's over-lapped and that I covered all the car with the 14 photos (I could have spent much more time on this!) – the results were staggering, autostitch managed to plug them all together and create one big photo that was 98% perfect. The remaining 2% could be easily touched up manually – brilliant!!!

    I'm looking forward to experimenting with this program and taking more impressive panoramic views!! :)

    Cheers Steve!!

    01 Jul 2005, 09:53

  3. John Rawnsley

    Here is a link to a panorama I made of pictures taken in Avebury at the weekend. This was 7 images hand stitched in Photoshop to give an 18048 pixel wide image then scaled down to 5000 (the limit for the website where it is located).

    01 Jul 2005, 10:13

  4. Paul Strapps

    John,

    That's quite impressive work! It's difficult to see the joins! Out of curiosity have you tried using Autostitch to put them together to compare the results??

    Paul

    01 Jul 2005, 10:25

  5. Steve Rumsby

    That looks wonderful! It is the sort of subject I've been looking for, and have never managed to get to since I got my camera.

    How long did it take to hand stitch it? I'd be interested in seeing what happens if you let autostitch loose on the same set of photos – does it do as good a job. I realise this will mean having to use a PC - if you can't stand the thought, send me the tiles and I'll do it:-)

    01 Jul 2005, 10:34

  6. John Rawnsley

    I haven't used Autostitch, but I've downloaded the demo version and will try it this weekend if I can borrow my wife's PC.

    The handstitching took about an hour using CS2 from 8MP RAW images. I chose one of the images to get the settings for the RAW import and then applied the same settings to all 7, pulling them directly into Photoshop's photomerge and saved them preserving layers. This gets them roughly positioned but does not do an actual merge. I did try letting PS do the stitching using the advanced settings but there were several quite visible joins.

    Then I started at one end and brought the next tile on top with 50% transparency to position it. I made it opaque and adjusted the exposure slightly to match at the overlap, then erased parts of the top image with a feathered eraser to get smooth joins.

    I can see some of the joins, and the exposure is not as even as I wanted even though I locked the exposure when taking the pictures. It was just a spur of the moment thing, and the results might be more even if I had had a tripod.

    01 Jul 2005, 11:41

  7. John Rawnsley

    I had a go with autostitch. It produced a more even exposure and colour balance but at 5000 pixels wide I could see JPEG artefacts in the image. When I tried to preserve the original resolution (18000 pixels taking into account the overlaps) autostitch ran out of memory.

    03 Jul 2005, 14:34

  8. Steve Rumsby

    The gala pano above is 8.9k x 1.7k full-size, which is some way short of yours. I've not tried to produce anything bigger with autostich. I imagine it can be quite a memory intensive process.

    I'd be interested to see the 5k wide image, to see how it compares to the hand-stitched version. Basically, I want to know whather or not it is worth putting in the effort to learn how to do it by hand:-)

    04 Jul 2005, 15:25

  9. John Rawnsley

    Basically, I want to know whather or not it is worth putting in the effort to learn how to do it by hand:-)

    I'm pretty sure that had I been able to get autostitch to handle the images it would have produced a more even panorama than mine. I had to feather the overlaps in areas without important detail and couldn't get an even exposure and colour balance without a lot of work, which I didn't feel like doing. If I had been making a panorama of a building, I couldn't rely on the randomness of the detail to hide the joins.

    The downside of autostitch is the immediate loss of quality involved in using jpegs for input. I used the batch tool in Camera Raw to import the RAW images directly in my hand stitched image.

    I'll find somewhere to upload the 5KP image.

    John

    04 Jul 2005, 16:18

  10. John Rawnsley

    The autostitch effort is here.

    One more point, I didn't spot how to embed a profile in autostitch. I also added an sRGB colour profile afterwards with photoshop as the colours looked insipid without it.

    04 Jul 2005, 20:49

  11. Paul Strapps

    I have to say for an automated process AutoStitch did an impressive job and it seems like a well written piece of software!

    Out of curiosity what was the spec of the PC you were using?

    06 Jul 2005, 11:38

  12. John Rawnsley

    It's a Packard Bell 2.5GHz Pentium 4 with 512MB RAM running XP Home.

    06 Jul 2005, 20:16

  13. Joris

    I keep getting this “out of memory” error. I have 2GB of RAM and have tried setting it to 1, -5, -1, 0.5 and 0.1
    There has to be a work-around, but I’m out of inspiration… Any ideas??

    05 Oct 2007, 18:44


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