We’re all familiar with panoramas shot with the camera held horizontally and created by stitching the short edges of each sequential picture together using a suitable software application. But have you ever considered what would happen if you turned the camera through 90 degrees and shot your panorama sequence in portrait format?
The issue was raised recently by reader, Frank Wilkinson, who wrote:
If a 35mm (equivalent) lens is used to take three overlapping portrait photos each about 1.4 aspect ratio, a new landscape picture can be stitched together covering wider vertical and horizontal angles as would be photographed by a lens of approx 25mm equiv. focal length. The new photo should however have about double the pixel count and should have lower distortion than given by most shorter lenses. The trade-off will be some loss of resolution in the interpolated overlapping regions. Is this a worthwhile approach to wide angle photography using currently available stitching or merging packages?
Prompted by this query, we set out to test Frank’s suggestion. We used Panasonic’s DMC-TZ15 camera for our test shots because its wide-angle setting is equivalent to 28mm in 35mm format. We also took some test shots with the lens zoomed in to approximately 100mm (in 35mm format). The first set of shots, taken at the widest angle-of-view, are shown below.
The four images used to create the panorama.
Having captured the shots, we stitched them together with the Photomerge setting in Adobe’s Photoshop CS3. (This setting is also provided in Photoshop Elements.) Other stitching applications could also be used. The screen grabs below illustrate the steps used to merge the images.
1. Open the images in the editing software and select the merging tool.
2. Add open files and activate the stitching process.
3. The result of the stitching. Note the distortion due to the wide angle-of-view of the 28mm (equivalent) lens, particularly on the right side of the frame. This happened because the photographer had to swivel more to include the rocks on the right side.
4. The stitched image must be cropped to produce the end result.
5. A shot taken from the same position with the TZ15’s wide-angle setting and 16:9 aspect ratio provides an interesting comparison to the panorama created by stitching the four vertical shots together. Shooting with the camera held vertically allowed more of the subject to be included but introduced some significant distortions. It also created a file that was more than four times larger than the wide-angle shot.
What happens when the shots for stitching are captured with a narrower angle-of-view? Essentially, the degree of distortion is less. However, more care may be required when determining exposure levels, particularly when covering relatively wide angles of view. The illustration below shows a stitching produced by merging four vertical shots taken with a focal length setting equivalent to approximately 100mm in 35mm format.
A panorama produced by merging four images shot with a 100mm focal length setting.
Merge Quality Issues
Three factors significantly influence the quality of a panorama: the resolution and quality of the original images, the similarity of the exposure levels of the original shots and the performance of the image stitching program. If any of these factors is sub-standard, the end result will suffer.
The first two factors are determined by the photographer. We recommend shooting with the largest image size and highest quality settings because the more data you start with the more flexibility you have in the editing process.
Be wary of using automatic exposure systems, particularly when brightness levels vary across the area you cover. The illustration below shows what can happen when the camera’s AE system is used for shooting a panorama with significant differences in brightness between adjacent shots.
Panorama stitching applications also vary widely in performance. Some can produce merges that require few or no subsequent adjustments, while cheaper applications often fail to merge images accurately, as shown in the illustrations below.
An example of the merging of the 100mm shots with a freeware panorama stitcher, showing the different perspective it creates. The enlargement below shows an inaccurate merge that occurred with this panorama, which is typical of cheaper applications.
How to Shoot Panoramas
1. Stand in a position that will let you cover the entire scene without having to move. Avoid scenes with moving subjects as changes in subject position will prevent accurate merging.
2. Working from left to right, take a sequence of shots, overlapping adjacent pictures by between 30% and 50%. Keep your feet in the same position and swivel from your hips as you pan across the scene. Don’t change any of the camera settings between shots and try to capture all the shots as quickly as possible.
3. Download your panorama shots to your computer then open the panorama stitching software. In most cases, the software will provide adequate guidance.