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by Max Lyons Late last year, an image was posted on the internet which was claimed to be the largest digital“photograph” ever. Here the photographer explains how he did it. And what‘s more, you can download the shareware used to create it! T he photo at right is a view from Bryce Point in Bryce Canyon National Park in Utah. Nice, huh? But we haven’t shown you the photo just because of its scenic beauty. This image is believed to be the largest digital photograph ever. If SILICON CHIP pages were five metres wide, this image could be printed at high resolution! The original contains 40,784 x 26,800 pixels – 1,093,011,200 pixels in total, or a little more than one gigapixel. Now you might think that it would be a rather impressive digital camera to take such a photo – and you’d be half right. In fact, such a camera hasn’t yet been invented. This image actually consists of 196 separate photographs shot with a garden-variety Canon D1, then stitched together into one seamless composite. I have been unable to find any record of a higher resolution photographic (ie non-scientific) digital image that has been created without resizing a smaller, lower resolution image or using an interpolated image. Here’s another way to think about it. Given that the resolving power of the human eye (under ideal conditions at the centre of the retina) is about one arcminute (1/60th of one degree). This image captures considerably more detail than I (or any other normal sighted human) was able to see with my eye when standing on the overlook at Bryce Point. Assuming one pixel per arcminute, an image with dimensions of 3780 x 2485 would suffice to capture the amount of detail that the naked eye could resolve. This image has more than 100 times this detail. Looking at the full sized digital image, one is able to see things that might have been difficult or impossible to spot, even when using binoculars. Below are some crops to simulate the amount of detail that would be captured using cameras of different resolutions (I don’t own any of these higher resolution cameras, so the crops below are simulated. Due to the resizing algorithm used to create these crops, they may over-estimate the amount of detail actually captured by these cameras). How was it created? The first step in the creation of the image was to choose an appropriate subject. There were a number of technical issues that I had to consider that are not normally encountered when taking single images. For example, it took me 13 minutes simply to take all the photographs and I was shooting as fast as my camera could write images to its memory card. So I needed a subject that was relatively static. Secondly, I knew that I would have to use a very long focal length lens to take the image, otherwise the final composite would end up with an extremely wide field of view. . . some- RESOLUTION: What does it mean? Each of these simulations shows the amount of detail captured shooting the same scene at different resolutions. While they are simulations, achieved by resizing the 1GB image) they probably err on the good side (actual results would probably be worse.) 76  Silicon Chip Unresized (1.09GB) 140 megapixel camera. 50 megapixel camera. www.siliconchip.com.au We obviously can’t do the image justice printed on a magazine page. In true life, it would be five metres wide . . . thing I didn’t want. This also presented challenges due to the extremely short depth of field when using very long lenses. The second step was to assemble the images. This was a complex and lengthy process. My normal procedure (using “PTAssembler” [see “About the software”]), Panorama Tools and Photoshop) was not sufficient in this case for a number of reasons because of the size and number of images I was working with. For example, the version of Photoshop that I use cannot work with images with pixel dimensions of more than 30,000. So, my solution was to 22 megapixel camera. www.siliconchip.com.au modify some of the existing programs in my workflow and write a number of new software programs to create this image. Why Bother? Good question. The short answer is “why not?” As digital camera resolutions have increased and the hardware, techniques and software for stitching multiple images into composites have improved, there has been specualtion about when gigapixel images would become possible. This seemed like an interesting challenge to me. (I still think that it will be a long time before true gigapixel 11 megapixel camera. 6 megapixel camera. cameras will become available.) However, this isn’t the only reason. I’ve been producing and printing stitched images consisting of 20-150 megapixels for several years. I’ve become addicted to the amazing detail that is visible in large prints from these images! Gigapixel images present the possibility of producing some of the most amazingly detailed prints at sizes of 10-15 feet wide. A 300ppi print of this image would measure about 3.3m wide, while a 240 ppi print would be close to 5m wide. Even printed at this size, the image would appear very sharp upon close inspection. 3 megapixel camera. February 2004  77 Another advantage to an image this size is the ability to crop very small portions of this image in a number of different ways and still produce extremely high resolution large prints. How do you print It? Another good question. The short answer to this is that there appear to be a number of alternatives, but none that I’ve discovered I’m completely happy with. So, I’m still thinking about it! However, I’m interested in hearing from anyone who would like to partner with me on printing this image. I think it would be an excellent match for (and an excellent demonstration of) large format printing technology. If you have an idea or a proposal, please let me know! About the software With time and patience, anyone can achieve the results seen on these pages. Basically, two programs are used: PTAssembler and Panorama Tools. In fact, you could use just Panorama Tools but PTAssembler will dramatically help you. PTAssembler is a Windows “helper” program for Panorama Tools, Helmut Dersch’s powerful panoramic image stitching software. Despite (perhaps because of) its numerous features and capabilities, Panorama Tools can be challenging to use. It requires a lot of time and effort to create the “scripts” needed by Panorama Tools to stitch multiple images into a larger panorama. PTAssembler is designed to make this task as easy as possible. No knowledge of Panorama Tools or its script syntax is needed in order to operate PTAssembler. I’ve been using Panorama Tools This shows the 196 individual digital photographs before they were stitched together to achieve the single 1 gigapixel photograph shown earlier. It took some thirteen minutes to shoot the series, as fast as the Canon 1D camera would allow. for a few years to create my high resolution images and continue to be impressed by its abilities. However, many people (myself included) find it extremely difficult to learn and use. I decided to write PTAssembler to make it easier to use Panorama Tools. Even with a “helper” program like PTAssembler, Panorama Tools is complicated and requires more input from the user to create a final panorama than many popular “automatic” stitching programs. But the results are worth it. With a little time, perfectly stitched panoramas can be created every time. Overview of panorama creation Stitching images together using Panorama Tools is a little different from most “automatic” stitching programs. For example, the user is required to set “control points” on each image marking features that appear in the overlap region between adjacent images. Unlike automatic programs, Panorama Tools does not know (and will not guess) how images should be aligned without these control points. Another aspect of using Panorama Tools that may seem strange to users who are used to automatic programs is its “optimiser”. The optimiser uses the control points to determine the best positioning for individual images in the final panorama. The optimiser also uses the control points to detect and correct any lens distortions (e.g. Here’s how it works, with (in this case) four overlapping photographs. digitally “stitched” together to produce one composite picture that would defy even the experts to pick! There are several fully automatic programs around which will do this simple task; none could possibly hope to handle a 1GB final image nor do it anywhere near as well! 78  Silicon Chip www.siliconchip.com.au barrel or pincushion) that can cause misalignments between images. PTAssembler allows the user to optimise all parameters necessary to create a panorama without having to write and/or modify scripts. Although Panorama Tools can output a final image in JPEG, TIFF (and other) formats, one of its greatest strengths is its ability to output a “layered” image file that allows the user to perform the final blending between adjacent images manually. Panorama Tools takes care of warping, aligning and positioning the images so that they line up correctly. However, you can choose to perform the final blending (i.e. decide the exact position of the “seam” between images) in your favorite image editor. For a beginners guide to creating a stitched image using PTAssembler, please refer to the on-line PTAssembler Tutorial at www.tawbaware.com/ptasmblr_tutorial.htm Also, complete documentation is included with PTAssembler but is also available on-line. Where from, how much Both Panorama Tools and PTAssembler are shareware; that is, they can be downloaded free of charge but a small registration fee applies. Some features may not work fully without registration. All necessary links for the software along with a large amount of documentation, examples, tutorials and further links (and much more besides!) may be accessed via the author’s website, www.tawbaware.com SC About the author/photographer . . . This is me. . . Max Lyons. So is the guy on my left, and the one on his left, and the... (not forgetting the one peeking in from the edge of the photo!) As you can see, I have a lot of fun “doing things” with digital photography. I’m the author of the software and photographs in this article. This isn’t my “day job” but I do spend a lot of time at it! I became interested in progamming and digital photography around 1996, after buying a “Teach yourself Visual Basic” book and a fantastically over-priced digital camera. The programs on my website (see below) are the product of a few years of work and far too many late nights... I have some other stuff on the web. There is the digital camera software (www.tawbaware.com), and some of my better photographs (www.tawbaware.com/maxlyons/ index.html). If you are moved to do so, you can email me at maxlyons<at>tawbaware.com. I promise I will read them all but as you might imagine, I get a lot of them so I can’t guarantee I will answer every one! www.siliconchip.com.au February 2004  79