Panoramas

Panoramas are an integral part of the architectural photographer's armoury. In general shots, which encompass a very wide field of view, especially if letterbox format, are termed panoramic. They come in a number of guises from the "pretend" cropping of a 35mm or APS format (into a wide-narrow shape) to the Fuji GX617 with its enormous piece of emulsion equal to twelve 35mm frames. Hasselblad make a 35mm pan format, the Xpan. Standing alongside these options are all manner of electronic and mechanical devices, which either spin the camera or spin a slot in front of the emulsion. To assist there are also a range of software options which stitch images together into passable arrangements.

Providing that you do not use wide-angle lenses it is possible to create a really high quality panoramic stitch using Photoshop or some other image manipulation software. This is the technique we will concentrate on in this feature.

There are five phases to the creation of a pan.

1. Ensure that the camera is mounted so that it can rotate evenly and in a plane level with your horizon. Use the camera in Manual exposure mode and manual white balance if appropriate.

2. Get the images into a computer by either shooting digitally or scanning.

3. In Photoshop align the elements.

4. Adjust the tone range if required.

5. Blend the elements using a layer mask.

Shooting

Care taken during the shooting will be amply repaid at later stages. The three most important things are to get the camera level (preferably using a spirit level), allowing at least 50% image overlap and shooting fully manually (so that exposures and white balance are all identical). If you have a clear horizon ahead of you it is possible to track the camera around and ensure that the centre of the lens stays on that horizon. Do not point the camera up or down to get more land of sky. If you need a wider view of the scene, put the camera in portrait orientation (assuming it is not medium format!)

If you shoot film and then scan, take extra care to line the scans as this will save problems later. If you think you are going to have trouble with alignment and thus need to rotate images, allow extra resolution to give yourself a few pixels in hand. Engage your brain before starting to scan. A 36-shot pan scanned off 35mm at 2700ppi will give you almost a GB of file - work out the size that you need or down-size a set of the images before you commence your stitching. The composite screen grabs show the stitch process in detail.

Output

Long thin pans look a little weedy on A4 paper. Epson make a panorama paper (which is an option in your "paper size") or you can use the roll feed on a modern printer. We output the examples three-up onto 24" paper on an Epson 7600, running off the roll at more than 5 feet.

Panorama

1. The two images to be stitched. The illumination fall-off is equal on both images at the matching ends.

2. The white remnant of the scan is first trimmed off with the Erase tool to show a definite edge.

3. Aligning the images now reveals the change in image density across the join line.

4. A Curves Adjustment Layer is added to the right hand image (uppermost on the layer stack).

5. The curve is adjusted so that the join line blends into the tone of the image below. This also lowers the tone of the whole of the right-hand part of the image, which is not desired.

6. A gradient is applied to the layer mask associated with the Curves Adjustment layer. This leaves the left hand part of the image matching at the join but leaves the remainder of the image to the right un-altered.

7. The image tones are now balanced up.

8. To control the blend of the image structure (i.e. the building detail), a Reveal All Layer Mask is added and a gradient is dragged between the guides, which mark the ends of the images.

9. The completed stitch is seamless both in tone and structural detail. Distortion of the image by the taking lens is accommodated by painting the mask so that only one version of the building structure is allowed to show in the composite image. This was true of the Radio City Tower.

The SWPP 2008 Convention was an outstanding success,
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