Recap: Can’t calibrate with April Tags. Tried A4 A5 and A6 prints with different distances, angles, orientations and room lightings. Inside and outside of laser case. Always “0 Markers found”.
Windows 10 PC, LightBurn v1.7.04 and Gweike Cloude Pro laser with bundled 5 megapixel fisheye camera fixed in center inside lid. 510x300 mm laserable area.
Calibrating with old circles image works although fiddly. Takes 15 minutes to get <= 0.35 on all calibration steps. Alignment then completes without issue. But end result is not super great. In bed center actual lasered position differs 1mm from camera position. But in outer corners up to 8mm.
Screenphoto of image shown after alignation laser step and calibration with old circles image. Notice how a chunk between 3 and 4 is blacked out, despite <= 0.35 calibration step results.
(BTW why not show a similar image and suggestions at calibration wizard end?)
v1.7.04 changelog has bugfix for extreme perspective overhead cameras, but didn’t fix my issue.
I wish calibration/alignment doc had more real world examples of how little deviation (in mm) can realistically be had in center and outer areas after careful calibration/alignment. I get that camera quality, fisheye degree and laserable area varies between lasers. But some examples could still help adjust expectations.
I’ll go bigger: I wish for a video where the LightBurn team completes the calibration wizard with april tags and fisheye cam and no parts of the video cut out. Ideally with split view between LightBurn window and sideview shot of hands placing/holding the april tags.
The image captures look like they might be out of focus. Hard to say from the screenshots. If they look blurry to you examine the camera to see if there’s a way to focus the lens.
Instead of trying to do the calibration with the lid closed I’d suggest pasting the calibration pattern to something rigid and handholding it. This will allow you to try many more positions to dial-in the calibration
If after camera alignment the alignment is still off then try this:
3a. Create a grid of squares across the entire workspace, then burn onto material. Do not move the material or modify your design.
3b. Capture an overlay
3c. Use the Camera Shift and Scale adjustments until the overlay matches your grid on workspace as closely as possible.
3d. Save the Camera Adjustments by right-clicking Camera window and selecting Save.
This looks like to me it’s due to that portion of the bed not being captured in the overlay.
I’ve tried both inside and outside the case. Alas, always “0 markers found”.
I think the issue is in calibration, not alignation.
Yes the input source does seem to exclude a portion of the honeycomb (or its edge really), but it seems like a bigger portion is missing after calibration, even with <= 0.35 results.
out of focus: I think LightBurn’s scaling in the calibration wizards window makes the image appear more blurry than the original source is. I’ve tried adjusting focus on the camera several times throughout my tests. No difference for april tags. Note also that I, with the same camera focus, can get <= 0.35 scores with the old image circles, even in not so great lighting tests:
I used an AI to quickly whip up a python OpenCV script that successfully detects 6 tags in that image (using cv2.aruco.getPredefinedDictionary(3) specifically). Which makes me think LightBurn is at least a part of the issue here.
Let me vent a little. To me the calibration wizard is quite bad and a timesink. Big contrast to the very user friendly and effective controls and tools in LightBurn in general. The wizard could be improved in many ways small and large
When we in old circles mode press “capture” with a keyboard the input focus moves to the “honeycomb check” toggle control. Which means I can’t just with one hand keep pressing “space” or “enter” to repeat capture while I adjust the circles with the other hand.
Why have the user make captures one by one at all? LightBurn could instead on “capture” press instruct the user to slowly move and angle the circles/tags and automatically capture and process multiple images per second until a really good capture is detected or the user presses a “stop” button.
The instruction says “Try to get the lowest score” but then specifies that “0.5 or less is ideal”. But my experience with <= 0.35 captures for circles is far from ideal. And if I intentionally go through the wizard with some higher values, like a 2 or 3 at some steps then the result is terrible, even though LightBurn at the step says “Not too bad!” (don’t recall exact phrase). What’s even the point of letting the user click next with scores as high as 10? Has anyone really gotten useful results with such high scores?
as mentioned in my first post, after calibration wizard there should be some extra step that guides the user to if the result is probably useful or not. Without having to spend time on the alignation lasering and clicking steps.
