Taking Panoramic Landscapes - The Easy Solution
I love panoramas. There’s something very appealing about their
shape. It’s probably because we see the world more in these
dimensions than the near square format of standard film/sensor
frames. It might also explain the upsurge in the popularity of
widescreen TVs!
Panoramas have a reputation of being hard to take. There are
dedicated panorama cameras available but unless you’ve got at
least a thousand dollars to spare, you probably can’t afford
one! But you can take panoramas with any kind of camera.
All a panorama is, is a sequence of images where you turn
slightly for each different frame. In the old days, before PCs
and the likes of Photoshop were around, you’d take your prints
(there wasn’t much point in shooting panoramas on slide film,
for obvious reasons), lay them out on a table and position them
over each other where they overlapped. A bit of sticky tape held
them together. [As a side note, this technique was used by NASA
to build up mosaic pictures of the planets and satellites their
spaceprobes visited, up till the late ’70s/early 80s when
computers were introduced to make the process less
laborious].
Now that PCs and image manipulation packages are easy to come
by, high-quality panoramas can now be created by anyone. If
you’re shooting slide or negative film, you will need to have
your images scanned before you do anything else.
DIY Panoramas
The idea behind taking panoramas with SLR cameras is that the
camera is rotated around its nodal point during each successive
exposure. What’s the Nodal Point? It’s the point inside your
camera where the light rays converge and flip over. It’s
different for different focal lengths (on zoom lenses) and for
different prime lenses (fixed focal length lenses like a
standard 50mm lens). It’s important to rotate about this point
to eliminate image mismatches due to changes in parallax.
Parallax is the apparent shift of an object against a background
due to a change in observer position.
Just to be clear, the Nodal Point is not the same as the
film/sensor plane. Generally, for most SLR cameras and lenses,
the Nodal Point is located somewhere towards the center of the
lens barrel and lies in front of the image/sensor plane.
The Problem With Parallax
Parallax is easily demonstrated by a simple experiment. Hold up
your finger about 1 foot in front of your face and alternately
open and close your left and right eyes. You’ll notice that your
finger shifts left and right with respect to the background
depending on which eye is open. Try another experiment: With
your finger still raised, close one eye and turn your head from
side to side. Notice how your finger moves with respect to the
background. This relative movement is due to the fact that
you’re not rotating your head around your eye’s nodal point,
which is somewhere in the center of your eyeball. Instead,
you’re rotating about your spine which is several inches to the
rear and off to one side. It is this relative side-to-side
motion that we try to eliminate when setting up a camera for
panoramas. [If you want to read up more about parallax,
href="http://en.wikipedia.org/wiki/Parallax">Wikipedia have a
good explanatory article.]
Now, if you consider a camera held up to your face - it will
suffer even greater parallax errors as it’s farther from your
spine (the point of rotation of your head) than your eye. It’s
surprisingly common for people to take panoramas in this fashion
and then find the individual pictures don’t match up.
So use a tripod and rotate the camera on the tripod. The
parallax errors will be significantly smaller but there will
still be some error involved. However, the images will match up
better than with the head rotation method.
Mechanical Contraptions
What perfectionists strive for is to have the camera rotate
about the nodal point. There are brackets and contraptions
available that will let you offset your camera from the tripod’s
axis of rotation and with a little experimentation and trial and
error, you can position your camera so that its nodal point is
directly over the axis of rotation of the bracket. Getting this
spot-on means your images should line up perfectly.
A few months ago I bought such a bracket - the Kaidan Kiwi. This
comes in two halves which produce an L-shaped bracket. Its
instruction manual explains how to set it up and find the nodal
point for your camera and lens. However, you have to get your
tripod perfectly level before using it, otherwise you end up
with a curved panorama rather than a straight one.
I’ve had good success using this bracket, but it is large and
heavy and certainly a bit too cumbersome to be carrying on long
walks or while away on vacation.
AutoStitch To The Rescue
Then I recently came across a free bit of software called
AutoStitch. Written by a couple of students at the University of
Columbia, this takes all of the heartache out of creating
panoramas. All you do is select the size of the final image and
tell it what images you want it to stitch. It then goes off and
produces your panorama.
It really is that simple. Unless successive images are radically
different in exposure (i.e. one image to too light or dark
compared to another), it seamlessly blends them. It performs all
the warping of the images necessary to get them to align (other
software I’ve used can cause ghosting in the overlap areas where
it hasn’t quite aligned the images). It also aligns multiple
rows of images rather than just a single strip.
Even better, it doesn’t require you to set up your camera to
rotate about its nodal point. When I was in Crete last year, I
tried shooting a few panoramas with my Canon EOS 300D held up to
my eye (I didn’t have a tripod with me). When I got home, I
tried stitching the pictures together using various bits of
software (including software dedicated to stitching images
together) and didn’t get satisfactory results. I knew, though,
that it was because I’d swivelled the camera about my spine. But
I tried these images with AutoStitch and they came out
perfectly.
href="http://www.great-landscape-photography.com/panoramic-landsc
apes.html">See for yourself here.
I went walking up the Wicklow mountains in Ireland no too long
ago and up to a high point called Djouce which offers a view
over the rolling hills south of Dublin. As an experiment, I shot
8 frames while rotating my head about the scene (camera to eye
as per normal). I wanted to see if the Crete photos were a fluke
as the panoramas from there were composed of, at most, 3 frames
each (sometimes 2).
Conclusion
What can I say? I plugged 8 frames into AutoStitch and after a
bit of time processing the images, it produced a perfect
panorama with no ghosting I could see in the overlap reasons. I
like software like that. It may only do one thing but it does
that one thing very well.
Give
href="http://www.cs.ubc.ca/~mbrown/autostitch/autostitch.html">Au
toStitch a try. It’s free and, so far, it produces the best
panoramic results of all the panorama/stitching software I’ve
tried.
One thing to remember when taking panoramas is that the
exposures of each frame should be the same. So if you make your
first exposure at f/8 and 1/125 of a second, take them all using
those settings. Yes, you will have to put your camera into
manual mode. Otherwise, you run the risk of having radically
different exposures for your images. For example, if you’re
panning over a landscape that contains water, like a lake, any
sunlight reflected off the water may make your camera take a
shorter exposure than for the other frames in your sequence.
Setting your camera to manual mode will prevent that.
About the author:
Gary Nugent is a software engineer by profession and has been in
the business for over 20 years. Photography has been a hobby for
an even longer period of time and he’s now even more passionate
about it since making the switch to using a digital SLR camera.
You’ll find more tips and techniques at Great Landscape
Photography: http://www.grea
t-landscape-photography.com