Even though Photoshop offers some rudimentary panorama stitching function, I am using something way better. Here is what you need to download to get the job done:
Autopano - A software that automatically figures out how to align the images (extremely helpful to make the whole stitching job as painless as possible).
Enblend - Makes the images fit seamlessly without any manual effort.
We are going to use Enblend and Autopano as Plugins to PTAssembler, so don't worry if the websites confuse you with command line parameters. We are not going to use it this way.
PTAssembler - A graphical user interface for the fantastic Panorama Tools Library (a free mathematical library for Panoramas and Mosaics). Just follow the installation instructions on the Website of PTAssembler. PTAssembler is available as a 30-day fully functional Shareware. You should really chose to register the software as it is very inexpensive for its advanced functionality. There are free alternatives, like Hugin, but if you ever run into problems stitching an image (if Autopano has trouble with large skies or other rather featureless portions), you will quickly come to enjoy the ease of PTAssembler. Additionally Max updates his software very quickly.
Other commercial tools are very expensive (like Stitcher) or offer very limited functionality (like Panorama Factory - no TIFF, only single row). The advantage of doing it my way, is that you can run everything fully automated, but you can still have full control for fine tuning as you become more advanced.
Lets open up PTAssembler now and go to File->Preferences->Plugin.
Here you will tell PTAssembler the location of Autopano and Enblend. You may reduce the /size:1500 to /size:1000 for faster results. The enblend parameters are:
-a assemble non overlapping images prior to blend
-m 300 use this much memory
I am using 300 on my laptop (512MB ram) but I am using 2500 on my desktop (1GB ram).
Edit: Actually Windows can only manage 2GB per process, so you should set a number below 2GB or enblend fails to run.
Enblend heavily swaps files on your HDD if it needs more than the specified memory. In my laptop I only have 512MB and I do not want Windows to have to jump back and forth between the Windows Page File and Enblend Swap files. On the desktop computer, I have multiple HDD. They all have a portion of the Windows Swap File. Therefore I expect faster performance when using the Page File (hence I tell Enblend to use more RAM than I physically have).
Now open up PTAssembler. Here is what it will look like. Click the "Add" Button and load your 8-bit images. Autopano only supports 8-bit images, therefore we need to do this step.
Once the images are loaded, simply click the "Auto-Create" Button and watch how smart the software is.
A DOS window will open:
and Autopano will do its job. Then you will see a window like this:
We do not want to stitch the final panorama, since we want to make some more adjustments and use the 16-bit images, but we do want to see if Autopano worked (So we click on No). Now Panorama Tools will do some Work and then we get a preview of the final panorama:
Don't worry about the black borders, we are simply going to cut them away. We can see that Autopano found out what image goes where in the final image but we also see where the seams are (They won't show in the final image anymore, after the next steps).
Lets make some final adjustments:
PTAssembler Step 5 Adjustments
Since we are going to use Enblend, we set the Feather Parameter to 0 (don't forget this). As the Output Format we choose TIFF / Enblend. This will automatically start Enblend and blend your images (make the seams disappear). Now we click on Auto Size Parameters one more time and then go to Step 2 (see button).
We will see the Settings Window.
As Interpolator we choose either Sinc256 or Sinc1024 for best quality.
In case you skipped the RAW step and shot JPG, or if your camera does not support RAW, you may have ended up with different white balance settings across your images or even worse with different brightness levels.
Here you have the chance to fix some of this by using the Color/Brightness Corrections buttons (do a preview first to see if it worked - Step 5).
Now we are ready to go to 16-bit. Save the project.
(File->Save Project). Go to your windows explorer and replace the 8-bit images with your 16-bit images. Make sure they have the same file name.
Now go back to Step 5 (see Picture to the left) and simply click the create button.
I recommend getting a beer now as this will take some time.
||After a while, you will find a large file xxx_enblend.tif in your output folder. This file looks just like the preview image. Crop away the black borders and you will have your final output (see left).
As you can see, there are no more seams visible in this stitched image.
Now you can do all your post processing you normally do on RAW converted images, like sharpen and color enhancements.
||Finally lets convert the color profile to sRGB and save it as a jpg file. As you can see, the final output is about 73.2 Megapixels large. And all of this was done with a 8.2 Megapixel Camera. You can go much larger than this, although I find that for most applications (printing) it does not make much sense.