Introduction to the Art of Photo Stitching
by Sandra Kehoe – December 21st, 2015
Guest Blog By X-Rite Coloratti Jason DiMichele
Introduction to the Art of Photo Stitching
For those not familiar with the term photo stitching, it refers to taking a number of slightly overlapped photos and using software to combine them into one large photo. The concept of photo stitching is not new to digital. For years photographers have been scanning photos shot with film and stitching them together using software.
A few reasons why stitching is beneficial include:
- Creating extremely high resolution photos (think hundreds of megapixels or gigapixels)
- Photos containing a wider angle of view (pano) than is possible with a single lens
- Creating photos with any desired aspect ratio as opposed to having to crop (and losing resolution) from a single photo.
Whether you’re using the stitching process to create a high resolution image or a wide sweeping pano, it’s important to keep in mind that this process is a tool to achieve an end result. Creating an image with strong composition is most important. If your resulting stitch won’t create a compelling photo, consider that the stitch may not be worth doing. Although the stitching process is an exciting one, remember that a boring image, regardless of size, is still boring. All of your regular compositional tastes and ‘rules’ should apply.
This article provides an overview of the stitching process including tools and technique, but for the sake of brevity will not go into all the fine details. I’ve tried to keep a balance of technical and best practice / technique so that this article may be of interest to a larger audience. I am more than happy to answer any questions you may have about the tools or process. I welcome your emails as I realize there are people at all skill levels and I’m always willing to assist. The details for the stitched image example used in this article include:
Camera: Fuji X-E2
Lens: Fuji 50-140/2.8 R LM OIS WR lens @ 140mm (equivalent to 210mm on 35mm)
Manual Exposure: 1/8 second, f/8, 3200 ISO
Resolution: 290 megapixels; will print at 170” x 53” at 180ppi (102” x 32” at 300ppi)
Total number of images: 56
Much like other styles of photography, some specific gear is required or convenient to have which will make the stitching process more accurate and repeatable. These tools don’t have to cost much; you probably already have some of them and the others you can either make yourself or use workarounds.
First up is the tripod. It is possible to create handheld stitches but it will potentially affect your overlapping consistency, your leveling and your composition. As with standard photographic technique, any tripod that keeps your camera sturdy will suffice. When stitching a number of images you definitely don’t want your camera swaying between shots.
Next is the remote shutter release. It is beneficial to avoid touching the camera as much as possible when creating a stitch as there are more opportunities to introduce vibration. You can use any type of camera supported shutter release. A remote shutter release cable or wireless trigger will help create sharper images. Using the built-in timer is okay but be careful not to press the shutter button too hard.
The most specific and potentially expensive piece of gear that is required (if not shooting handheld) is the pano head. The pano head is required for calibrating lenses or specific focal lengths on a zoom lens to a point where there is no parallax distortion. We are all familiar with the effects of parallax; hold your finger out in front of you and alternately close each eye and you will see your finger shift with whatever is behind it. There are some pano heads (spherical) that will allow you to create multi-row and those that will only allow a single row. They range in price from under $100 to $1000. I started out using a homemade bracket and a number of years later purchased the Nodal Ninja Ultimate M2 with the RD8-II rotator base. It is a beautiful piece of equipment to work with and allows me to produce very repeatable stitches with my lightweight Fuji X series equipment and my heavy DSLRs with pro lenses. There are many examples online for plans and ideas on how to make your own pano bracket. Proper calibration is critical when objects are both close and far away from the camera. For subjects that are on a single focal plane and further away, the effects of parallax won’t be much of an issue. To calibrate a lens/focal length for accurate stitching, you need to adjust its position (forward or backwards on a spherical head) on the pano head so that the camera rotates around the lens’ no-parallax point (or entrance pupil). There are many resources where you can learn how to calibrate a pano head. Make sure that before you begin taking the required photos that you tighten any adjustments on the pano head so that nothing shifts during the capture.
Leveling your tripod and/or pano head is important ensuring that each photographed row is straight, allowing for a better stitch as well as not having to crop as much after the stitching process. A leveling head is a great tool for expediting the levelling process. It sits under your pano head rotator base or pano bracket and allows you to level up the pano head without having to adjust all three tripod legs individually. If you don’t have a leveling head, the use of a bubble level affixed to the top of your tripod works well.
The X-Rite ColorChecker Passport is an essential field tool as well. It is small, light and protected in a hard plastic case. For accurate color, you’ll want to photograph the ColorChecker Passport before you begin photographing the photos for the stitch. Photographing the ColorChecker Passport just before taking the photos for your stitch is also useful as a beginning marker for the photos that are to be included in the stitch, making it easy to differentiate between stitch jobs. Back in the studio you can also use it to create custom DNG camera profiles. X-Rite also has many great tools for calibrating your monitor (and printer) at various price points. These devices are a great investment. If you are putting all of this effort into creating stitched images, it doesn’t make sense to not have complete color control and accuracy.
Using equipment that enables consistent color accuracy will allow you to use additional techniques with the stitching such as high dynamic range (HDR) imaging or focus stacking. HDR being a method of creating a pleasing exposure by blending underexposed (for highlight detail), normally exposed and overexposed images (for shadow detail). Focus stacking is a method of achieving unlimited depth of field by blending images taken at multiple points of focus.
There are many options for stitching software, the more popular ones being Autopano/Giga (Giga for supporting the stitching of gigapixel images), Hugin, PTGui, Lightroom and Photoshop. I have used Autopano from Kolor for years and am always pleased with the results. Its default settings work very well and the advanced features are very powerful. I find that dedicated stitching software does a superior job compared to the stitching features found in Lightroom CC or Photoshop CC.
The software I use for my stitching workflow includes Lightroom CC, Photoshop CC, Capture One Pro and Autopano. I use Lightroom for cataloging all of my images as well as some RAW processing. I use PhaseOne Capture One Pro for processing my Fuji X-Trans II RAW images as well as some of my Canon DSLR RAWs. Currently I find that Capture One Pro produces better RAW conversions for the Fuji files and often for my non-Fuji RAW images as well. I do not recommend using Autopano for RAW conversion. I prefer Lightroom for everything else once the RAW images are converted. I use Photoshop for the post processing functionality that Lightroom can’t provide (advanced cloning/healing, more complicated selections, etc). I use Autopano for the actual image stitching process.
Tip: When preparing your images to send to Autopano, I suggest making only minor global edits if necessary and do all of the more detailed adjustments after the stitch is been done.
The following is a list of best practices to help you produce high quality stitches:
- Using manual focus tends to provide the most accurate results. If you use autofocus (which works ok for distant subjects without close foreground), pay attention to where the camera has focused. Using manual focus will also allow a more accurate focus blending process should you require the use of that technique.
- Shoot RAW for ultimate flexibility.
- Use a manual white balance for an easier post processing workflow. The use of the X-Rite ColorChecker Passport will allow for a very accurate white balance.
- Although Autopano will do a decent job at blending exposure, it’s best to employ manual exposure for accuracy. Using manual exposure will also be of benefit if you decide to use high dynamic range (HDR) imaging for your pano.
- Use a good combination of aperture and ISO to obtain a reasonably fast shutter speed to mitigate any potential vibration or blur from long exposure. Using mirror lockup or a mirrorless camera (Such as the Fuji X series) will assist in making your images as sharp as they can be. As for choosing the aperture, your choice will depend on the standard depth of field concerns. Note that in a pinch it should be fine using a smaller aperture (f16-f22) since the effects of diffraction won’t be as noticeable at the sizes most of your stitches will be viewed or printed.
- I recommend using a tripod whenever possible. Using a disciplined handholding technique can also provide good results. Shooting handheld you may want more of a per-shot overlap (horizontal or vertical between rows). If shooting handheld, I suggest using 40-50% overlap vs 20% when using a tripod.
- Compose your stitch a bit wider for some cropping insurance should something have gone wrong during the shooting process or if you change your creative mind post shoot.
- Before the first image of each row in your stitch, take a photo of your hand (perhaps holding up the number of fingers representing the current row) or ColorChecker so you can easily group subsequent images and stitches of the same scene without confusion.
- When photographing the images for your stitch, try to position yourself in the middle of your scene so that the amount of panning left and right is equal. This will ensure that you get consistent depth of field.
The process for stitching a group of images in Autopano is as follows:
- Browse to RAW converted images on your hard drive or export them from Lightroom.
- Click on the detect pano button. I find that the default settings work very well, especially for simple stitches and during the Autopano learning phase.
- Click on the edit pano button.
- Choose the projection you would like to use. Often the default projection is a good start, but sometimes choosing another projection works better for a particular image. The discussion of a projection is beyond the scope of this article.
- Click the crop button to crop and rotate the image to your liking. You can also use the Yaw/Pitch/Roll tool to straighten your image.
- I suggest leaving any color processing for Lightroom or Photoshop, especially until you become familiar with how Autopano handles color. Autopano does not read the tagged ProPhoto RGB color space on your images but Lightroom and Photoshop will properly apply the ProPhoto RGB color space when completed. This tagged color profile behavior in Autopano is not an issue with the AdobeRGB or sRGB color spaces.
- Select your desired batch rendering options. If your image is greater than 30,000 x 30,000 pixels (the Photoshop pixel limit), you will need to use the Photoshop PSB file format.
TIP: Before processing your full resolution stitch, try exporting all of the images to Autopano at a much smaller resolution to verify that the stitch was successful.
When you import your image back into the Lightroom catalog, you can use the stacking feature to group all of your images together. To make your stitch the top image of the stack, press SHIFT-S. The use of color labels (instead of star ratings) makes it easy to spot where all of your stitched images are.
Here is the final image showing 100% unsharpened crops. The detail is incredible:
I hope that this introduction to the art of image stitching has sparked your interest in exploring the technique, or taking it a step further if you already incorporate it in your photography. I’ve just scratched the surface of what is possible with image stitching but even with basic skills and technique you can achieve some really great, high-resolution images.
X-Rite color solutions – www.xritephoto.com
Adobe Lightroom CC and Photoshop CC – www.adobe.com
Kolor Autopano/Giga – www.kolor.com
Fujifilm X Series – http://www.fujifilm.com/products/digital_cameras/
Nodal Ninja Ultimate M2 – http://www.fanotec.com/
Capture One Pro – www.phaseone.com