This topic is somewhat new to me and I only started using this technique some years ago and wanted to share my excitement and experience.
When I travel, I only have a limited time at a certain place without the comfort of taking a day to scout the area and then coming back the next day to shoot. I do my scouting online as much as I can, so I don't run into unexpected issues. I've learned this the hard way, but I suppose all tough and valuable lessons come that way and I am happy to learn.
The use of this technique came to me on a road in the mountains somewhere in the US. I'd seen a video about it, but didn't fully grasp the concept then. I suppose the best way to learn these things is by going out and taking photos and then seeing what works and what doesn't. The tricky part is that you only see the final result at the computer when you are putting the photos together. Luckily Photoshop has an automated thing for doing such things and all you have to do is tell it which photos you'd like to merge, and then sit back and relax :)
When shooting, I try to overlap the photos enough from the previous shot, it's better to have more shots than not enough. Some say that you should overlap 1/3 of the image and you can take this as a loose rule. I've had times when I've taken 8 shots, but then used 6 or maybe even less. It depends from the scene you shoot. It's interesting, because it seems that a more complicated visual scene is easier for the computer, than a simpler one. I guess it makes sense, because there are more key points to latch on to, because once I had a very interesting experience with a minimalistic shot where there was only a boring sky on top of the photo, and grass on the bottom. A straight line separating the two. The point of interest was a small chapel. The photo seemed super simple. The overachiever in me obviously took more photos than necessary. Guess what, Photoshop could not put it together. I even tried with more or less shots. The grass from the left side was stretched and pulled all the way to the sky. It was bizarre. I ended up stitching the photo manually and everything was fine. It's been a few years since that happened and maybe Photoshop's technique has improved. Update, no it hasn't and you can see these fine example below starting with the tree in the foreground :)
Which lens to use? This is the fun part and I like getting creative with this. Whichever one I use, I shoot vertical, which is the whole purpose of me blabbering about it. This is the biggest difference when using simply a wide angle lens vs let's say a 50mm. I want my panoramic shots not only extend horizontally, which is what we usually associate the word panoramic with, but also vertically. This way I get more real-estate in the height of the photo. The final effect when you look at the photo should be as if you are really there in the scene. By doing these stiches, you also get some massive files with a lot of Mpix, which comes in handy if you want to blow it up or do some cropping and still have plenty of resolution for great prints. However, back to the lens change. It also depends from how far you are from the subject of interest. I often use my 70-200mm lens at the focal length of 70mm. Again, if it's a mountain range far in the distance or a cityscape across a large body of water, I might zoom in more. This is simply trial and error and depends of how I envision the final result. When I bought my Canon 50mm f1.2 I thought I'm gonna love it and initially I did, but somehow with years love fades….and… Anyhow, most of the time it's on the shelf, but for these vertical panoramic shots I find that 50mm is a really good focal length. However, if I'm traveling abroad, I will not take that lens because it's heavy and I might not use it. I'll be alright with the 35mm instead.
The technique itself of taking these shots is rather important, because if I do a good job, then later when Photoshop does it's merging magic, I will lose less of the image along the edges, because Photoshop auto content-aware fills in the missing parts. If something looks funky, I can get my hands dirty and retouch it myself. It's best if I can do this on a tripod, then it is pretty straight forward, however, I must confess, sometimes, if I'm in a rush or placing a tripod is not an option, I will use my body as a tripod by rotating my upper body. Most of the time I get pretty good results. Of course, tripod is still a preference and even more so if you do these stitches combining with long exposure photography. I have a smaller travel tripod with markings on the panning axis, that makes things relatively easy and repeatable.
As you can see from the post image, it is also a very valuable technique if you are into realestate photography. This photo was taken with the Canon TS-E 17mm f4 L lens and there are two shots combined. This doesn't really count as a vertical stitch, because it was a horizontal shot, but eh, rules are meant to be broken :) If you are not familiar with the tilt-shift lenses, in short, you get to keep straight lines in your images without any distortions. Obviously you still need to follow some basic rules to get those straight lines. In this particular shot I did a pano with the lens shifted up and then down.
Keep in mind that there is no camera movement, only the lens.
Once I've captured the image I will make my selection in Bridge and then open the files in Camera Raw and see if I need to make any color/exposure adjustments for smoother stitching. Sometimes I will do more than that before the stich and sometimes I will do the heavy lifting after the stich, that's a case by case decision. For merging in Bridge I go to Tools--->Photoshop--->Photomerge… Photoshop opens and you are presented with various options. I leave the Layout to Auto (should be the default option) and I check all the boxes at the bottom. By default only Blend Images Together is selected. Feel free to experiment with the settings as this is simply my workflow. I've always used these settings regardless of the orientation of the pano, and only messed with them if something is not working :)
I want to share an image which was clearly an overkill, but this was one of those situations where I was driving by and didn't have much time to spare and the rain helped keep me moving along rather briskly. I knew that I wasn't gonna come back anytime soon, and because of the lousy weather, the conditions were kinda perfect - Dark and gloomy, just how I like it :)
The more I look at this image, the more I get the feeling, that I shot it hand held and that's why the ridiculous amount of images.... Can't recall... Those of you not in your twenties will be able to relate to this problem :D
As you can see from the layers and what PS used, I could've easily used less images. This also resulted in a PSB file since it was a hair over 3GB. If you are curious, the limit for PSD files is 2GB and you will definitely find that out very quickly on your own once you start tinkering with this technique :)
This overkill of a shot resulted in a whooping 31000 x 8784 pixels! This would make an amazing large print. Also, if you would zoom in on the original photo, it's like using binoculars.
I love this technique, but sometimes I find myself in the trap of doing the same shot, but in different focal lengths, and the process gets even lengthier if it's a long exposure shot. On top of that, the stitching process in post can take a few minutes, but that solely depends on the power of the computer, but on slower systems it can even become unresponsive and/or crash. But don't let that stop you from being creative, it's still worth it!!! :)