by Alfred Rijnders
(This tip was submitted by a user.)
Occasionally I like to play around with stitching images into panoramas.
My standard recipe for creating panormas
Use a good and simple lens like a 50mm prime instead of a (super)zoom lens. The simpler the lens. the fewer
corrections for barrel distortion, pincushion and vignetting you have to do afterwards.
To prevent vignetting, also be sure to stop the lens down far enough (> f/8).
All this helps in making the stitching process easier and in making the seams invisible.
Focus once on the most common distance for all of the images and put the lens in
MF before the actual shooting (you don't want different focusing between the images).
Meter the scene and choose an average metering that does not overexpose on the
brightest image (you want the same exposure across all images).
Set the camera in manual mode and use the metering found in point 2.
Use a fixed white balance (you don't want a different color temp between the images because
this will be apparent immediately).
Since I'm using raw I don't care much on white balance during shooting:
I'll set it afterwards during the processing of the files.
Use a tripod and be sure to have the camera level with the horizon (also during rotation).
The better you do this the more successful the stitching will be.
For Kodak SLR/c Users
With other cameras my recipe would end here.
However the slr/c images I wanted to stitch didn't seem to have the best "lens optimalization settings."
On causual inspection I didn't notice this, but the slight difference in color cast
between the left and right hand side of the image was apparent immediately
after stitching, making the panorama look rather bad.
So I had to add the following step to my recipe:
Optimize your lens optimalization settings , preferably beforehand in the camera. If this fails you have to adjust the lens optimalization manually in photodesk to do away with the cast
Adding this step gave me very good results.
Putting it All Together
Using Photoshop CS
I've included a sample of a (to some a familiar)
river scene. I created the panorama using the photomerge functionality of photoshop cs.
This functionality proved to be challenging too.
It's important to use the advanced blending mode to get good seams between the images.
The quality of the seam is especially apparent in the running water and the green foliage.
However, photoshop introduced a slightly darker band over the seam that I could not get rid of.
This band is especially apparent in the sky (cloned it out a bit).
This is a shame because apart from this I really like the result of this functionality.
Here's a link to a panorama I made using Photoshop CS's photomerge function (462KB).
After some web browsing and advice from other photographers,
it was clear to me that Panotools was the way to go if you want full control over the process.
Since Panotools is open source and thus free it was not hard to decide on.
However, no normal photographer would only use Panotools to create panoramas.
This is because it is more or less a "panorama engine" that requires scripts with
instructions to get it to do some work. It's a necessity to use Panotools together with a
GUI front end. Since I have a Mac that I use for my photography work I
used ptmac (www.kekus.com) as the front end.
Even with the help of a GUI you are still confronted with an intimidating amount of parameters! A lot of these parameters have to do with correcting lens faults. In fact Panotools has a lot of very sophisticated corrections for vignetting, barrel distortion, pincushion and chromatic aberrations that you can put to good use even if you don't do panoramas at all. Luckily, if you use a good and simple lens (preferably a prime), and stop your lens down enough to prevent vignetting from happening in the first place you don't have to mess with this stuff.
What is important though is setting up control points between the different images. These are matching points in the overlapping area between different images. A lot of your success depends on getting this right and it is not always easy to do. The authors of ptmac currently have a beta tool (xpoints) that finds the matching connection points automatically. This doesn't always work, but it sure helps. Using this you only have to correct a few erroneous control points and you are all set. After I got the hang of this process I got good seams again, but still with brightness variations in the sky...
I was about to give up but then I stumbled upon another tool called enblend. Enblend is not a panorama-stitching tool like Panotools, but it is intended to use in addition with it (or your other favorite panorama tool). You must set Panotools to export the panorama as multiple tiffs first. After this enblend blends the corrected images together. Enblend uses some clever mathemathics to do this in a way that areas with low frequency detail, like skies, get a smooth blended seam. Areas with high frequency detail are blended together without the smoothing taking place.
Trying this out (I used xblend which is a mac version from the same authors as ptmac) after the stitching process gave the most beautifully blended and seamless panorama I could ever wish for! (Without any manual editing at all) Finally my panorama is beginning to look like the fantastic ones I've seen on the web.
Now all of the above looks like a very complicated procedure. Well it is at first, but once you get the hang of it isn't that difficult. You have to get used to the terminology and you have to know the parameters that are important and the ones you can skip. There are a lot of good tutorials on this if you browse the web and if someone wants to give it a try I can always be of help too...
Here's a link to a panorama I made using PanoTools (872KB).
Some useful links on all the stuff I used:
Ptmac (includes a distribution of panotools for Macs)