Can't get good lens calibration after following all the instructions

Been working to get better lens cal in my 16MP Arducam. Great camera! But my first cal was a bit dicey- you can adjust the X/Y offset/width to dead nuts on any 2 points on the bed, but other points were often 2-3mm off due to limitations in the lens cal. Much more so near the edge. Glued the card to wood, no wrinkles, focused camera, covered the honeycomb.

This is with the door interlock disabled and the door left open- plus a lot of the error was left/right offsets so zero chance it’s the door stability. I covered the honeycomb. Other complications- this is a 1.6mx 1.0m bed, it’s huge. The test card is small. Also the 16MP Arducam was supposed to be 105deg FOV, but it appears wider than that. At the time, I was forced to use the set screw for the lens that came with it- those are awful. They’ll crush the bottom of the tube without really locking the lens focus. And when you do try to tighten it, it shifts the lens and throws off the focus you just set, and shifts the alignment too. But I changed to a threaded locking ring and it’s great now!

So I took the camera off, put the test card on the floor, played with the lighting, but got mediocre scores. Better than 1, but rarely near 0.3, again, limited accuracy.

Next I took some Youtube advice. Lifted the card so it fills approx ~1/3rd the screen width, and tilt it so its normal vector points to the camera. Bad scores or failed detections ensued.

I was concerned it’s somewhat out of focus at this point. So I got white posterboard, lasered the pattern into it, and laid it on black foam-core board, WAY bigger than the printer page, and filling 1/3rd the total FOV width when laid on the bed where the camera is focused. I think it looks pretty good now, close to the “do this” picture. Tried it with interior lights on and without. But, ZERO recognition going on most of the time, and when it did score, it was a high number. Tried covering up the black sides of the card too, again no joy. At this point I can’t see any benefit to removing the camera again to try to cal off the machine with just the larger card.- there’s nothing about the machine likely to be interfering. Anybody see something I don’t? Why is the cal so unhappy?

BTW, I have a zoomable M12 lens on order (you need to get the non-“IR” one, which would mean it has an IR cut filter so it’s not flooded with invisible light that maps to a wrong color. I don’t think the Arducam has a cut filter with a regular lens. The zoomable lens should hopefully still have enough FOV to see the whole bed, but if I can match up the FOV to JUST the bed, the image resolution per mm is going to be much higher all over.

Moved discussion over to prior thread, plz delete this thread if you like

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