PTGui Tutorial: 3 Panoramic Photography Tips and 5 Editing Techniques
Before stitching, make sure you know these 3 rules to take 360 images properly
1. Avoid parallax, use a panohead or philopod
Parallax is a phenomenon where two objects in your source images appear to have changed their relative positions from one to another, because of changes in the camera's perspective. To avoid having stitching errors, we recommend that you avoid having parallax at all costs; that is also to say, ALL of your images to be stitched into a panorama must be shot from ONE single viewpoint.
The viewpoint for your camera lens is its entrance pupil, also known as no-parallax point or nodal point. Now suppose if you mount your camera on a tripod and start turning it on its base, the lens/perspective is constantly changing as you take images for your panorama. And that is NOT what we want.
To solve that problem, you need to attach a panoramic head, panohead for short, onto your tripod, to help rotate your camera around the front of the lens.
If you don't have a panohead, you can also craft a philopod, which is a piece of string tying the no-parallax point of your camera at one end with a weight at the other end. This technique is also explained by its inventor, Philippe Hurbain on his personal website.
That way, by having your camera swiveling on a fixed point, you have ensured that the perspective remains the same, and saved yourself the headache of having stitching errors.
Watch this tutorial by Florian Knorn for some basic techniques in getting the images you want, and see a panohead in action.
2. Make sure everything is on manual mode
Lock your exposure by selecting the Manual mode on your camera, so all your images will be taken with the SAME exposure settings. If your camera doesn't come with the Manual mode option, you can still count on PTGui's Blender to smooth out the differences in brightness.
Set the focus on Manual too; Lock the white balance in your camera, which you can choose to use the camera presets.
You can check out this Manual mode tutorial for DSLR cameras by CNET for more tips.
3. 20% Overlap between images
Approximately 20% overlap between your images should help PTGui recognize where each image goes in your panorama without problems.
Editing with PTGui
Load images: Load your images into the Project Assistant by either clicking on "Load Images", or using simple drag-and-drop;
Align images: PTGui can automatically detect overlapping details on different images, where the software will set down control points, to project them altogether into a panorama; when it fails to do so, you will have to manually select control points with the Control Point Assistant; create at least 4 pairs of control points to evenly cover the overlap. You can click and drag to change the position of the control points, or right-click to delete them. You can check the Control Point Assistant tab to see if you have enough control points yet;
Optimize images: Run the optimizer to make sure the control points are matched as closely as possible;
Make sure all vertical lines are parallel, and straighten the image horizon.
Choose your projection:
Rectilinear: Less than 120 degrees of field of view;
Cylinderical: Panorama onto a flat surface;
Equirectangular: Full spherical image;
Crop your image: You can drag the vertical and horizontal sliders to resize your image, or drag on each edge of your image to resize asymmetrically.
Fix blending faults with masking.
Create panorama: Set size manually or go with the default optimum size, select the file format and output layers, and save the file.
Straighten the horizon
A distorted horizon when you load your panorama set into PTGui can be the result of either your camera changing in position during the photo shoot, or if an anchor image was rotated during optimization.
You can click on the icon in PTGui to correct the image horizon automatically or pull it straight manually.
You can manually straighten your panorama when you have the Panorama Edit mode on:
1. Left-click on a point on your horizon and drag it to the central crosshair of the editor;
2. Right-click on a second point that isn't on the middle horizontal line of your panorama editor yet, and drag it on that line;
Now your image is straightened out.
Watch this video tutorial by panoramasdk to recap.
Mask moving objects and tripods
Masking is frequently resorted to when there are moving objects in your panoramic images that result in doubles, or when you don't want to see your tripod showing on the nadir image. This technique is used to fix blending errors.
With PTGui, you can paint the objects you want to mask out in red or green, but notice that red is for hiding objects from your final panorama, while green is for preserving objects so they come out visible in your output.
With that principle in mind, if you:
Want to block out the tripod, you need to paint it red, which you can encircle with the Draw tool and fill your enclosed object with red using the Fill tool;
Want to make an object that's currently hidden visible again because it's cut into two by a stitch seam, you need to bring out the Detail Viewer and choose to "Show Seams". Now you are able to find the source image where that hidden object from the panorama is on; paint and fill that in green using the same two tools explained above. Now if you check on the seam again, you will notice that it has already moved.
Watch this video tutorial by Florian Knorn for a full walkthrough.
HDR (High Dynamic Range) photos and tone mapping
Dynamic range is a photography term, referring to the range of light intensities from the darkest shadows to the brightest highlights in images. DSLR and mirrorless cameras typically have larger sensors, and feature a wider dynamic range than compact cameras with smaller sensors.
In a longer exposure, details in the shadows will be distinct, but highlights might appear washed out, as typical of a sunrise/sunset shot; in a short exposure, however, highlights can be exposed properly, but darker objects will descend into an unrecognizable mess.
HDR photography aims at overcoming the limited dynamic range of the camera sensor, by combining multiple exposures of the same scene ("bracketed" exposures) in order to maximize detail in light and dark areas. They combine the exposure brackets shot in camera to produce an HDR image.
If you own an SLR camera, turn on and manual mode and use its automatic bracketing function (which is otherwise unachievable through digital compact cameras), to take a sequence of images with varying exposure times.
Tone mapping is a method for HDR imaging and printing, considering CRT and LCD monitors and printouts have a more limited dynamic range than achievable in an HDR image. This technique maps one set of colors to another to approximate the appearance of HDR images.
PTGui will detect bracketed images as their exposure times follow a pattern, and ask you if you want to link the bracketed images. Once linked, the images will be treated as a whole, with the same yaw, pitch and roll; if your images were taken handheld, however, choose to enable HDR mode but don't let PTGui link up the images.
PTGui has two workflows for HDR images: You can choose to go with True HDR, which creates an HDR panorama and has it tone-mapped to a printable image; or you can go with Exposure Fusion, which tone-maps your panorama directly without generating the HDR panorama first. You can toggle between the two options under the Exposure/HDR tab.
This video tutorial by HDRPhotographyPro explains the workflow for Exposure Fusion.
For True HDR, you will need to:
1. Change to Edit Individual Images mode in the panorama editor after the images imported have been aligned and control points generated, and edit each image under their correspondent numbered tab;
2. Under the Create Panorama tab, set a name for your output file, and select the EXR output format. Choose to output both 'HDR panorama' and 'Tone mapped panorama';
3. Adjust your Tone Map Settings under the Exposure / HDR tab. Drag the sliders and see how the preview changes, until you get the result you want. Click "OK" to save your settings Adjust the sliders until the result look satisfactory and press OK to save the settings to the project;
4. Create your panorama, which outputs two files, one .jpeg file for the tone-mapped panorama, one .exr file for the HDR panorama.
For Exposure Fusion, you will need to:
1. Change your Fusion Settings while monitoring your preview;
2. Create panorama.
Here are two full tutorials by PTGui and Florian Knorn on stitching panoramas with PTGui. You can also visit Florian Knorn's panorama tutorials playlist to gain more insights.
Hope this has helped you. What other tutorials would you like to see? Let us know in the comments below!