Thursday, November 27, 2008


I have been using Photoshop Elements as my main photo editing package.  It does a great job for the price and I suspect will be adequate for me for some time (until I realize how much working in 8bits is hurting my post-processing).

One thing that has astonished me is how well it handles panoramas.  I had previously taken a few (perhaps 3) photographs in landscape mode and used photoshop to stitch them, but more recently I tried to take 2 or three layers of pictures of a scene and left photoshop to figure out how to stitch them.  The main reason for going this route is that I wanted to get a scene that had the aspect ratio of a regular scene but covered around 180 degrees.  My camera's standard lens is a 18-55mm so with the lens on 18mm you can cover a fair amount of ground

To be clear, there are limits to how well this works.  For starters, I have been careful to
  •  maintain a top to bottom, left to right sequence and shoot each photograph in portrait mode
  • set the exposure to a constant value - in brightly back lit scenes this can be tricky, but if you choose an average exposure for the scene you can use the inherent exposure flexibility in raw to selectively brighten or darken to get the correct effect
  • focus on somewhere about a third into the scene and go for a small aperture so that you don't get variable focus in the scene
Admittedly, the computer takes considerable time to churn through a scene that is around 20 photographs in size and the psd file that results is huge (hundreds of megabytes).

Once the photograph is stitched, photoshop gives you multiple layers with each component that it has broken down for the stitching.  I usually use Merge Layers and quickly resize it to roughly what an ordinary photograph would be so that I can deal with a more or less normal file size.

Of course if you have taken the sky and something very close to your feet as the vertical range, there is considerable distortion - but I am happy to live with that for the added bonus of including the entire scene.

By way of example, here is a scene shot with my regular 18mm.  The scene is from the eastern head in Knysna, South Africa - a spectacular opening into the sea that is apparently quite a feat to navigate into when the weather is bad.

The scene was shot with a polarizing filter which accounts for the graduated blue in the sky.

I also took 17 (and I see now that these were in landscape mode) separate photographs of the scene which I then stitched together.  I didn't adjust the polarizing filter so the darker sky is still relative to the position of the sun with an apparently even graduation as the camera was moved from left to right.

The distortion is most obvious in the bottom part of the photograph.  I was pointing the camera almost directly down and the notch inward is not accurate - the inlet runs more or less straight from the sea to the town - but in my opinion this rounding effect is perfectly acceptable for the additional drama that is captured in the scene.

I have been following Panorama Paul's stream on flickr for some time now - he has an interesting technique for vertical panoramas which he began as a result of his disappointment with automatic stitching and with the fact that you can't blend two photographs where the is variable focus between the foreground and the background.  More on this and a link to Paul's tutorial later.

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