Thursday, September 07, 2006

Panoramic Technique

Cousin Paul mentioned that uncle Francis might be interested in knowing how to create a digital panorama like the two I've put up here before(this one and this one), so here's my two sen on how to do this.

It's not hard to create a panorama from a bunch of digital photos, but you need the right software. You also need either a camera tripod, or a steady hand to hold your camera and rotate it. If you just google for 'free panorama software' or something like that there'll be a bunch of links that should point you in the right direction. There's a bunch you have to pay for... try to find one that's easy to use and free. It's been a while since I experimented with software that's available online, so I'm not familiar with the free panorama software that's out there now... these days I use the software that came bundled with my Nikon. They all work off the same principles though.

All panorama stitching software will need you to provide photos taken from a single point, with the camera rotating around that point. The important things to remember when taking the digital photos for the panorama are:

1) Keep the center of the camera in the same place as much as possible. Moving the center creates parallax motion between the images, and the stitched panorama will be distorted. For this reason, if you're taking pictures by hand, scenery that's further away tends to produce a better looking result that stuff that's close-up (like in a tight, enclosed space). If you use a tripod, this shouldn't be a problem.

2) Keep the vertical orientation of the camera constant (try not to tilt it). Again, this isn't usually a problem if you have a tripod.

3) Try to keep an approximate 50% overlap between photo pairs, and make sure there's enough detail in the scenery so the software can merge photos accurately. Also, the details should be fairly spread out. Panorama software works by finding the correct transformation between two images that it is trying to merge, and it uses these detail points to figure out how one image maps to another. Trying to create a panorama of a room with bare walls or an outdoor area with nothing but blue skies and little or no detail on the ground is usually futile.

Once you have your photos, plug them into your software and follow the instructions. Some software allows you to manually select corresponding points between photo pairs, to make sure the merge is accurate. If your photos were taken well, though, most of the automated algorithms used these days should produce acceptable results.

That's it! Have fun!

4 comments:

Tropicalplantman said...

Dear Bernard
Thanks for your advice. I had a Nikon that could produce panoramas but I now use another camera without such facility. The kind of panorama that I saw posted on the web page of Lijiang Old City was something different. Nor only could one turn 360 degrees horizontally but also vertically from ground to sky -- useful for showing architectural features inside a building or in a city.

greyhoundbus said...

Yes, a spherical panorama is much harder to do with a normal camera. I browsed a bit and found this page which has a section on making a spherical panorama with a normal 18mm lens camera. It says you need a spherical pano-head (sounds like a tripod that lets you pitch the camera up and down as well as left and right), though maybe the "steady-hand" technique might work too.

It also says you need software that stitches multiple rows of images. He has links to a few software sites, but I've yet to check em out. Sounds like sphericals are quite a bit of work. I might try it someday just to see if I can pull it off.

lawmanthoughts said...

Was wondering how the tripod was invisible :-))

lawmanthoughts.

greyhoundbus said...

Now that's a trick I'm not sure about yet. They obviously are made using special tripods/lenses, but I've not seen one yet so I don't know. My best guess is a tripod that suspends the camera by the sides (so it can tilt up or down and there's nothing below the camera blocking the view), and the legs have wheels on the bottom that are locked so that they rotate the whole tripod in a circle. With that setup you take pictures without ever seeing any part of the tripod.

That's just my guess, though. Who knows.