> For the complete documentation index, see [llms.txt](https://docs.theiamarkerless.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.theiamarkerless.com/troubleshooting/error-messages/calibration-errors/too-few-chessboards-detected-less-than-25.md).
# Too few chessboards detected (<25)
### **Explanation**
This error message arises when processing a lens calibration trial, and Theia fails to detect sufficient chessboard instances to properly calibrate the lenses.
### **Possible Solutions**
Check that the correct trial videos were loaded. If the intention was to process a lens calibration trial but the incorrect videos were loaded which do not feature a calibration chessboard, this error will arise.
If the correct lens calibration trial videos were loaded, check that the chessboard pattern is sufficiently visible throughout the recording. If the videos are too dark or too bright, try using the [Enhance Videos](/theia3d-documentation/theia3d-dropdown-menus/tools-menu/enhance-videos.md) to improve the visibility of the chessboard pattern. If the chessboard is too close to the camera during the trial such that pattern is too large and is never fully visible, a new lens calibration trial will need to be recorded.
If there are no issues with chessboard visibility and it is fully visible throughout the recording, check that the Custom Chessboard options were not enabled when processing the Lens Calibration. If this options is enabled but the input values do not match the chessboard pattern in the recordings, this error will occur.
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