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it's not easy...

Creating panoramic images is more than just pasting a few images together.

The human eye sees the world projected onto a sphere that wraps around your body. The center of this sphere (or two slightly overlapping spheres, really) is in the middle of each eye.

Photographs are small pieces of that world sphere that you see, that have been squashed flat for printing on paper.

When you try to put these flat pieces of paper back together again, they never really line up properly. If you have ever tried to build something round with flat stuff, you'll know the problem.

The problem gets worse when you add the different exposures for each photo. Modern cameras with auto exposure will determine the best exposure for each shot. However what is "best" for one shot will probably be a bit different for the next shot.

What you end up with is a series of lighter or darker images so that the composite panoramic image looks striped with dark and light vertical bands.

If you try a full 360 degree panorama outdoors, at least one of your shots will be into the sun and one will be directly away from the sun. This will result in a large exposure variation acrcoss the shots, and a very banded image.

so how do you solve these problems...

This is where our panospace™ technology comes in.

If we are trying to do a 'humpty dumpty' and re-create a sphere from a bunch of pieces, then we need to bend these flat pieces into round spherical pieces.

It turns out that the radius of the sphere is related to the focal length of the lens that the image was taken with. A wide angle lens creates a tighter sphere with a smaller radius, a telephoto lens with a longer focal length will create a larger sphere with a longer radius.

You also need more longer focal length shots to cover the same amount of area as fewer wide angle shots - sorta logical isn't it.

This is where the computer comes in handy.

Digital photographs are just an array of pretty coloured dots arranged in rows and columns across a flat page. With some fancy cartesian to polar coordinate mapping mathematics is is possible to distort the flat array of coloured dots into a partly spherical array of coloured dots - ready for joining with other similary distorted images to form a panoramic image.

Daltech, my software company has developed our own panospace™ software for image distortion and stitching. This software takes camera settings such as focal length, exposure data and sun bearings for outdoor shots and uses it to adjust spherical distortion, exposure values and light polarisation to create seamless, consistent exposure images that make you really feel like you are part of the image.

the equipment...

We use several cameras depending on the situation.

Nikon Coolpix 850 - A little 4 megapixel camera that is absolutely bullet proof. It's relatively low cost makes it ideal for extreme situations. Most of the aerial shots have been taken with the Coolpix mounted to a glider or powered plane wing or tail. Shots are either taken with the built in timer, or triggered by a very long home made remote shutter release gaffa taped to the plane.

Minolta Dimage 7I - A very versatile piece of kit that copes with anything except low-light focussing. The lens on the Minolta is a gem - wide angle (28mm) to telephoto (200mm) allows it to capture and frame just about anything. 5 megapixels is enough detail for most outdoor shots, the ccd has relatively low noise and the colour reproduction (especially blue skies and water) is amazing.

Konica Minolta A2 - This is basically a Dimage 7I with an 8 megapixel sensor and a 1.1 megapixel electronic view finder. The anti-shake mechanism is very useful for low-light hand held situations (such as panoramics of exotic car dashboard or engine bay shots).

Nikon D100 - Is the implement of choice for all indoor shots and action shots. Very fast auto focus, great flexibility with shutter and aperture settings, crystal clear lens, but doesn't seem to capture the great outdoors as well as the Minolta.

Tripod Mount - To minimise problems with spherical distortion and image stitching, we have built our own panoramic tripod mounts specifically for each camera. Theoretically, the center of our sphere of view is in the middle of each eye - so too with the camera.

The 'hyper-focal point' is the point where the light converges to a single point within the lens. By rotating the camera around the hyper-focal point the center of the sphere of view is always consistent.

Since the hyperfocal point is inside the lens (and that will move with different focal lengths in zoom lenses) a special camera specific tripod mount needs to be made. We make ours out of 12 mm perspex sheet that is folded to form a bracket to hold the camera at the appropriate point over the tripod swivel point.

 

   

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