Before processing images taken with a fisheye lens determine the Horizontal Field of View. Take a picture of a distant building that has a continuous straight-line feature that runs end-to-end near the top edge. Open the image in PTGui and visit the Lens Settings tab. Lens type should be Circular Fisheye. Next adjust the Horizontal Field of View until the straight-line feature is truly straight. You can examine this in the PTGui Editor (Ctrl-E) but, better yet, visit the Preview tab and verify it is straight in a large image. This will take a while but, once done, you can apply it to all images taken with this lens. For my lens I changed the default from 180° to 168°. Ignore the fact that the lens focal length changes as a result of this calibration.
Open the PTGui Editor and drag the Horizontal and Vertical sliders so that only the image appears. You will be changing these settings for each image but this is a good starting point. Then visit the Create Panorama tab, specify JPEG quality of 90% (100% creates ridiculously large images), and Blended panorama only. Now save your settings. Choose File > Save as Template. I use two templates: one for Rectilinear and one for Vedutismo (Panini) images. Vedutismo works well if your images don't have obvious horizontal straight-line features near the top or bottom edges.
I have two templates that are included in this download:
- Samyang 7.5mm Land Panini.pts
- Samyang 7.5mm Land.pts
The templates work for images in landscape orientation taken with the Samyang 7.5mm lens. After extracting the files open PTGui, choose Tools > Options, and click on the Folders & Files tab. There it will indicate the location of the templates.
In PTGui you can choose a Rectangular or Vedutismo projection. When compression is set to zero the results of both methods are identical. While compression can be applied to a Rectangular projection, I often prefer the results obtain for Vedutismo. With this in mind my workflow is as follows:
- Open the image and specify the focal length as indicated on your lens (7.5mm in my case)
- Choose File > Apply Template for a Vedutismo projection
- Specify Vertical/Horizontal control points as needed and run the Optimizer
- Reset the sliders in the Editor so the maximum image area is exposed. For example, move the Vertical slider until transparent areas are seen at both top and bottom. Then back off so that a transparent area only appears at one end.
- In the Create Panorama tab click on "Set optimum size" and choose Maximum size
- Choose Create Panorama
- Choose View to view the results in Photoshop and crop as needed
Exporting the entire image from PTGui gives you the freedom to select any portion of the image in Photoshop. Specifying maximum size ensures the best quality.