Smart Cropping to get a sharper Panorama

<<How to>>

Part I

Foreword

"Smart Cropping" possible object and purpose have been shown in a previous page (click on "WHY WOULD YOU SMART-CROP?" button from the navigation bar at the top). This is now the "How To" Smart Crop photos for a 360 x 180 panorma.

The following tutorial is based on Canon EOS 20D (2,336 x 3,504 pixels / 15.0 x 22.2mm CMOS Sensor) and Sigma EX 8mm Fisheye lens.

I was reluctant to publish this first part as it does not learn to much that is new. It's trivial, but as it is somewhat the palatable basic forerunner of more sophisticated and obscure chapters, starting with Part II (click on "HOW TO, Part II" button from the navigation bar at the top)), I have selected to write if anyway.

First method: Crop in a graphic Application and Stitch in PTGui or PTMac

I personally used Adobe Photoshop (PS CS) "Crop Tool" to crop the photographs.

An Action was saved to clip the image down to its square hart (2,266 x 2,266 Pixels from original 2,336 x 3504 Pixels).

In portrait mode this came out as (35; 2901) horizontally and 619; 2885 vertically for the PS CS "Crop tool" location setting.

This setting was selected in order to have clipped photographs limited to 109,6 degrees angular Field of View (fov) and be then able to be supported by all new functionalities of PTGui 5. Click on "WHY WOULD YOU SMART-CROP?" button from the navigation bar at the top for details.

For the sake of completeness, six images centered in the horizontal plane (and spaced equally by 60 degrees), plus one for the Zenith and another for the Nadir were used for the PTGui 5 side of the demonstration.

On contrario, only 6 images were used for the PTMac side: four in the horizontal plane (90 deg spaced), plus one for the Zenith and another for the Nadir.

This set of 6 images could provide the best sharpness for a panorama with the 20D/8mm combo while shooting a reasonable low number of photos.

(I normally use only four in the horizontal plane and furthermore often skip the Nadir and Zenith shots for "non-architectural" photography).

Illustrated Workflow for the Stitch in PTGui alternatively PTMac (Click on Picts to Enlarge)

Project assistant Tab (PTGui) FOV=109,698 degrees is just below 110 degrees.

Lens type is Fullframe (i.e. rectangular shape)

Source Images Tab (PTGui) The Zenith and Nadir Shots are here placed first and second in the list. Eventually this shall has no effect because the images are cropped.

Note the dimensions = 2266 x 2266

Source Images Tab (PTMac) There are only six images in this case:

one has to set control points manually with PTMac and I am lazy !

Lens Settings Tab (PTGui) This are final values obtained after optimization.

The individual lens parameters option is unused as all images have same shape and dimensions.

Lens Settings Tab (PTMac) There are only six images in this case:

One has to set control points manually with PTMac and I am lazy !

The lens type is fullframe for all images

Panorama Settings Tab (PTGui) Standard settings for a Full spherical equirectangular panorama

Panorama Settings Tab (PTMac) Standard settings for a Full spherical equirectangular panorama

Crop Settings Tab (PTGui) Note that no crop is done here on any of the Eight images as it had been already performed in PS CS

Crop Settings Tab (PTMac) Note that no crop is done here on any of the Six images as it had been already performed in PS CS

Images parameters Tab (PTGui) The settings come from the final optimization.

The unusually high "c" value is due to the smaller than usual cropped area.

The distortion is thus much less than this would usually imply.

Images parameters Tab (PTMac) The settings come from the final optimization.

Here "c" was kept at zero...

A bug created some artifacts in the Thumtail images

Control Points Tab (PTGui)

Note that they are well spread apart.

The CP were created by the auto creation by PTGui.
Control Points Tab (PTMac) The CP Pairs were manually set of course as PTMac has no CP autocreation yet :-(
8 CP pairs were requested for each pair of images

Optimizer Tab (PTGui) All images have had identical parameters and coefficients. Optimizer Tab (PTMac) All images have had identical parameters and coefficients.

Preview Tab (PTGui) I rarely use this functionality. These are default settings, I imagine.

Create Panorama Tab (PTGui) One of numerous possibilities as the FOV<110 degrees allows using PTGui new internal engines. Create Panorama Tab (PTMac) Standard presentation.

Panorama Editor (PTGui) Looks fine even if smooth blending is lacking here... Panorama Editor (PTMac) Looks fine even if smooth blending is lacking here...

Conclusion

The benefit of the cropping is illustrated in a separate page. Click on the "SYNTHESIS / Illustrated Comparison" button on top of the page

Pros:

Cons:

Note (1) : this could be less a drawback as previous conversion from RAW needs often to use a specific S/W. The later could also be used for cropping as well in one go.