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Failed to detect 'Checkerboard" calibration pattern in this frame.

Please help me figure out the problem. When shooting using Alexa 35 and an anamorphic lens, it is not possible to recognize the grid.

In addition, I would like to clarify how to correctly specify the size of the camera sensor for anamorphic lenses, since when entering the pixel size value, it goes beyond the sensor.

#PFTrack

4 comments

Comments (4)

Simon

May 23

Hello Poll,

The sensor diagram in the Clip Input node is showing the unsqueezed sensor area used by the virtual camera model that PFTrack builds internally, which is why it's extending beyond the size of your real-world sensor. If you've selected the sensor preset and shooting mode from the menu choices then this will be fine, otherwise you just have to enter the full sensor size in the top and right-hand edit boxes for X and Y (hover your mouse over the box the see the description of which is which).

If you're having trouble calibrating a grid then if you can upload a sample frame here we can take a look and see what's wrong.

Simon

May 30

Replying to

It looks like the problem is related to the anamorphic squeeze - we'll take a look to find out why this is happening, but in the meantime you'll be able to calibrate your lens if you un-squeeze your grid images and media. I used the ARRI Reference Tool to export an unsqueezed grid image (i.e. one with square pixels at a resolution 4608x1582, although you could double the horizontal size instead of halving the vertical). In PFTrack you'll be able to load this grid and locate the checkerboard. Make sure you tell it you're using an anamorphic lens, but in this case the squeeze will be 1.0. You'll also have to enter the horizontal sensor width that you'll find in the EXR metadata.

Edited

Failed to detect 'Checkerboard" calibration pattern in this frame.

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