Posted by: David Vernon | June 9, 2009

Pano-rific

Peoria Sunrise Pano 1

Another lesson we spend time on in the Intro course at the Peoria Art Guild is on how to make a panoramic image. So what defines a panoramic image. Obviously it’s a very wide, or very tall shot. I like to think of panoramic images starting at an aspect ratio of at least 2:1 – at the very least. When you shot film, a traditional pano size was 4×10 – which is an aspect ratio of 2.5:1. Nowadays I like the Mpix sizes 5×15 and 10×30 – which are of course aspect ratios of 3:1. I think in the end, like a lot of things, you know a pano when you see it – and it’s a great way to really increase the drama in your image. So how do we get there?

The first step approach is easy. Take any normal image and crop it. And then walk away. You’ve eliminated the things that don’t make the picture any stronger – additional foreground or sky for example – and you’ve left behind all that counts. This is the simplest and quickest approach. Here are a few panos I’ve made from cropping a single shot into a panoramic perspective:

Golden Gate Nearby Pano

San Francisco, CA: Aspect Ratio: 2.5:1

Crater Lake in Black and White

Crater Lake, OR: Aspect Ratio: 2.5:1

Start 3

Detweiller Park, Peoria: Aspect Ratio almost 4:1

All of these shots are cropped into the essential element – and no more.

There is a downside to creating panoramic images this way. Since we cropped, we’ve actually thrown away pixels and made the image smaller. That’s not a big hairy deal if you’re just showing this digitally – on a screen or in a blog article. But if you want to print, you’re compromising your ability to print very large – and believe you me – panos are best seen BIG.

So how best to get there? The answer is STITCHING. And it’s a lot easier then you might think. Let’s take a look.

The image that led this article – the skyline of Peoria on a crisp October morning – was really 12 photographs made into one final image by digitally stitching the images together. For a lot of years, stitching software was slow and somewhat inaccurate. Nowadays, stitching software not only is fast and smart, but it will blend images for you to further hide alignment points. Photoshop and Photoshop Elements have it built-in. Photoshop is nice because you can work on RAW files – but taking your JPEGs and stitching can work very well too. For those of you who don’t use Photoshop, I can heartily endorse a FREE piece of software called Auto Stitch. It works specifically on JPEG files and it does a superb job. But it’s not enough to just go out and grab a bunch of shots to stitch together. There’s a process of course.

CREATING THE MOSIAC

The simplest approach to creating a multi-shot panoramic is just to pan through your scene, overlapping each successive image by some amount until you’ve captured the entire shot. You might in fact have a “panoramic assist mode” if you own a point-and-shoot camera. This feature will actually show you the previous picture you shot at the same time as the LCD is showing you the current picture the camera is seeing. Line the two up and you know you’ve got it covered. But if you’re shooting a DSLR – well – you’re on your own. But there are some things that can help.

First, you’re best off shooting this on a tripod. And if you’ve ever wondered why tripods have little bubble levels – well – here’s one good reason. You must be level to make your panoramic image work – especially if you’re just shooting one pan. When the software stitches the image, it aligns consecutive images based on commonalities at the overlap points. If you’re running downhill say – instead of level – you have fewer common points as you work across the image. The resultant file may be severely cropped as a result – with an exaggerated aspect ratio that is almost unusable. Level – in any circumstance where panoramas are concerned is better – and a tripod will help that. If you don’t have a tripod, you’ll need a lot more shots to cover your bases. That’s fine – but it will take longer to shoot, and it will take longer to stitch.

Next up is how you pan. I don’t mean left-to-right or right-to left – I’m talking about panning around the nodal point. The what? The nodal point. Now having said that – let’s not sweat too much what the nodal point is (it’s actually a point that’s parallel with your sensor) – let’s just say it’s important to have a tight rotation. If you’re on a tripod you’re going to stay very close to the nodal point. You’ll be fine. You can buy an expensive panoramic tripod head (I have personal experience on this front) that will get you perfectly over the nodal point – but frankly (in retrospect) for most work it’s overkill. A tripod is plenty. What you want to avoid – particularly if you’re using a point and shoot – is holding the camera far from your body when you shoot and pan. This puts the camera far in front of the nodal point and leads to… parallax.

BEWARE OF PARALLAX

No – that’s not something out of Jabberwocky. Parallax is a phenomenon that occurs when you make the simple mistake in shooting your panoramic images of operating too far in front of the nodal point. When you’re shooting at the nodal point, all the resultant images will be parallel. If you’re far in front, you’ll get a parallax effect. Frames in the middle will be straight, but frames on the outside will tend to run uphill to the middle. Take a look at this example – where I held the camera at arms length while taking the images:

Finding Parallax - Far in front of the Nodal Point

Finding Parallax - Far in front of the Nodal Point

Just looking at these images immediately gives the impression that they are not parallel. The left side image is definitely going to struggle matching the middle. The further I panned away in fact, the worse it got.

When we stitch something like this together, the software does in fact struggle to line things up at the intersections:

Parallax strikes back - Stitching errors

Parallax strikes back - Stitching errors

So work level, and work on a tripod – or at least very close to your body. What else?

Let’s talk about overlap. From the images above of the bridge you can see that I like a decent amount of overlap. You just need to make sure you’re covered. More overlap means you won’t leave a hole somewhere in the final stitch. I like about 30% overlap between pictures, but you can overlap as much as you want. More overlap means more images but surer coverage. Also – if you’re using a zoom lens – watch where you operate. I wouldn’t zoom too much wider then say 35mm. Again, a wider zoom means more stuff fits into each shot but it also means you might start getting distortion onthe edges – which will make stitching difficult again. I like to work between 35mm-70mm – it seems like a good compromise between eliminating distortion and not getting to many shots.

Let’s talk about settings. This is big. The one thing you don’t want is your exposure to change with each shot. What I like to do is put my camera on auto (let’s say aperture priority) and meter off the most important part of my shot. I’ll then take those settings and set them manually. Same with ISO, same with white balance. I don’t want anything to change as I execute my shots. This will really help hide your stitch points – even if some parts of your shot are a little over or under. But mostly things will turn out just fine. So manual is key – even if you arrive there with a little help. If you’re shooting a big distant landscape, focus is usually not an issue – but if you’re working in close – let’s say shooting around a table of people, you may need a lot more depth-of-field to carry the day so that everyone is in focus. Racking (changing) focus between shots again may complicate stitching.

There are other tidbits of course. Don’t limit yourself to horizontal panoramics. Vertical panos work too – but keep in mind that  as you tilt the camera up the subject is going to start running in and narrowing from the edges. If you can get yourself a little elevation for a vertical shot – well it never hurts. And certainly don’t limit yourself to just one pan. The bad stitching example is one pan of three shots. The downtown Peoria shot that started this off, like I said, was 12 images stitched together. But it was three pans of four shots. I started high – made a sweep for the sky, then tilted down and did it again, then tilted down and did it one more time. Here are the 12 shots before stitching:

Pano03

The great bonus in stitching is you get huge files. These were taken with a 6.1 megapixel camera. So with no overlap that would be about 73 megapixels. Even with significant overlap – about 65% here – I still end up with almost a 24MP image. I’ve printed this photo up to 42″ wide so far and found no issues at all. Big is suddenly a possibility.

In the end, once you have good starting images, your software will do most of the hard work for you. And the nice thing is the software itself is so easy to use – one or two clicks and you’re on your way. A little post-assemblage cropping and you have a wonderful piece of work. The folks at Digital Photography School have a nice article on creating panos – and they have a nice gallery of stitched shots for you to see. Let your mind wander and give this a try; meanwhile I’ll leave you with a few of my other stitched panos.

Pure Pittsburgh PNC Park Pano

3 Images - shot with an 11-18mm lens. Wider is possible - but stitch carefully

31 Winds

12 Images - 6x2

Soft Windows on Wind Turbines

3 Images - digital matte added for variety

Illinois Shakespeare 2008

20 Images - 10 x 2 - for the upper shot of Ewing Manor

And with that I’m outta the house for a few days – taking a little photo trip to parts unknown (to you not to me) but far afield from Central Illinois. I’ve got some very helpful guest bloggers lined up for the next few days. It’s always good to get a different perspective so enjoy what they have to say and we’ll see you on the flipside.

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Responses

  1. A couple of things I’ll add:

    1. When doing a horizontal pano, I usually have the camera in portrait orientation. It takes more shots, but, you are less likely to end up with something like a 10:1 ratio.

    2. Make sure to get extra space on the edges, so if you have to straighten / crop after the stitching, you have a little breathing room.

    I can’t tell you how many times I had it in frame, but, once stitched, an important edge / tip was clipped off. But, then again, I have had more success with handholding a pano than using a tripod. :/

    Oh, and if you make any adjustments to the individual frames before stitching, make the exact same adjustments to ALL frames. 🙂

    Nice writeup!!

  2. […] I mention this because I love to put panoramas together and a few moons ago we put together a “How-to” for panos right here on the CIPB. Take a look then head over and join the free contest at the […]

  3. […] Panorific – Everything You’ve Always Wanted To Know About Panoramas […]


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