Cropping images

[3DEnthusiast]

Hi there,

Is it acceptable to crop an image that is intended to form part of a Zephyr photogrammetry dataset ? I sometimes end up with unwelcome intrusions at the edge of my shots when shooting photos for inclusion in a dataset and am curious to see if I can safely crop these out or not.

[cam3d]

Hi 3DEnthusiast - Cropping, especially irregular cropping of images, is not advised and will likely cause reconstruction failure or sub-par results.

You want to maintain the original dimensions and resolution as shot, moving the camera closer instead of cropping out data from the captured images.

That being said, have a go and see for yourself! Trial an error is the best way to learn :-)

[Andrea Alessi]

And to build up on what cam said, simply use Masquerade to mask out whatever it is you want to exclude

[SimonBrown]

The path of light - from subject to sensor - is a critical factor for success. Cropping does not change the path, but automatic calibration will not be able to resolve the path of light correctly.

Like Andrea says, use masks to exclude areas of the image that have no value, or are causing alignment issues.

We have recently updated our Zephyr Foundation course and included a lot more content that covers using masks and we teach an example where we move the subject in the scene to shoot both sides, and use masks to force Zephyr to ignore the background.

So we can use source images like these:

And this:


And derive a model like this:



This bulls skull dataset is included in the course as a download, along with some sample masks created in Photoshop along with the Masquerade techniques taught.