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How I Process Panoramas

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In my last post, I discussed how I shoot images for a panorama. This time, I’ll walk you through my post-production process for making a final, composited image. Again, this is pretty simple stuff – I like to keep things simple whenever possible.

We’re going to be working with an older panorama for this example. I shot this pano at sunrise at Fords Pond, in December of 2009. It’s comprised of 6 images. Once my photos are downloaded from the card, I find the panoramic series in Bridge and tag them. (The tag is just a visual reminder to me that these photos go together, so that if I save the RAW files, I’m able to remember this in the future.)

Although I shoot in RAW, I don’t do any processing to the images at this point, except to apply the lens correction profile in ACR. Then, with the necessary images selected, I click Tools → Photoshop → Photomerge.

Photomerge is Photoshop’s image compositor. Choosing this command will launch Photoshop, and the Photomerge menu will appear, showing a list of files to be merged, as well as several options for how to merge them. I leave this set to Auto. (Note: you can also skip Bridge and launch the Photomerge window from within Photoshop itself, then select the files to merge. I like my way better, because I like Bridge.)

Photoshop does all the heavy lifting from this point on. Depending on how many photos you are merging, the size of your RAW files, and your computer’s hardware, the actual composition process may take anywhere from a few seconds to…well, I had one run for a half-hour once. In CS5, Photoshop opens each image and adds it to the growing panorama as a layer, although I can’t see the finished image until the very end. What I will see is a series of status bars, and as well as the growing layers on the Layers palette.

This is a hardware-intensive process. The pano I shot this past Sunday had 26 images in it, took about 10 minutes to assemble, and resulted in a 1.56GB layered file. I’m working on a desktop computer running a 2 Ghz quad-core processor with 6GB of RAM. Watching its performance on the Task Manager, both the processors and the RAM maxed out. The processor is what it is, but more RAM would definitely have helped my computer out.

Once the photomerge finally finishes, it’s the moment of truth. You’ll see the final panorama, with each individual image existing as its own layer, blended to the layers on either side of it. What you might notice, looking at the composited image, are thin lines that appear on the boundaries between layers. Don’t panic! These won’t appear in the final image, it’s just PS showing where they are.

Your job right now is to zoom in on the image and examine it for merge errors. Most of the time these will be obvious: cut-off objects, strange color/exposure swaths, etc. But sometimes they are small and subtle. Take the time to look now, because it really sucks to share a final pano image with someone, only to have them come back with, “Yeah, but what’s that weird place way down in the bottom left corner?”

Once I’m confident that the merge was successful, I flatten the image. This reduces the file size markedly and makes it much easier for the computer to continue working with it. My first step is to straighten the image, using the Arbitrary Rotation tool until the horizon is as level as possible. If I’m going to try and correct any perspective shifts, this is the time – although they don’t always work and can result in increased distortions. Next, I crop the image down. I simply clear out the crop tool’s fields and draw it across the image, keeping it as tight to each side as possible without including any empty (non-image) space.

Sometimes, if it will improve the image, I’ll include small amounts of empty space, but only if they are in areas where I can easily fill them via Content Aware Fill or the Clone tool. (Think small patches of sky, grass, etc.)

After this, it’s business as usual. I generally save the flattened, cropped panorama as a TIFF file and close it out of Photoshop, then reopen it in ACR. I’m a huge fan of ACR and like the way it works. I’ll perform basic exposure edits here, apply a digital graduated filter if necessary, and sharpen the image before returning it to Photoshop for final edits, including Curves, spot removal/healing, etc.

When I’m completely finished, I again flatten the image and re-save the TIFF file. I don’t really care what the dimensions are at this point, because I do most of my image posting/sharing in the digital environment. If I need to make a print of a panoramic image, I’ll bring it back in Photoshop and crop it to print dimensions at that point. This can be a little frustrating, since the selection of available print sizes is limited and it can be had to find a crop that is both flattering to the image, and fits the paper sizes. In these instances, I’d rather crop too large than too small. Meaning, I’d rather crop to include an inch or so of empty space at the bottom of the image, as opposed to leaving out elements by cropping into the image. Fill the empty space with black and add some text – the title of the image, your name, etc – and it looks great.

And there you have it – that’s everything I know on the topic of panoramas. Hit up the comments to tell me what you think, if I left anything out, or if you have a better way of doing it.

Brent Pennington

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2 Comments to How I Process Panoramas

  1. January 30, 2012 at 06:57

    Interesting that you convert from Canon RAW files to DNG files. Care to tell us why you made that decision? Perhaps that’s a topic worthy of its own post.


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