> The latter is coming closer to the reality, but not sure it's accurate
> enough as yet. May be there was a gap between the finger and the sensor
> when trial x ray was taken as our attention was on usb interface rather
> than lengths (getting computed length smaller than the actual one of the
> portion of the finger). I need to go and gather more x rays carefully (may
> be using a coin to make the boundaries more accurate) before confirming
> which measure is accurate or whether something else is required or is just
> a fixed calibration factor is needed.
There's actually pre-made x-ray markers for that
https://veterinary-instrumentation.co.uk/catalog/product/view/id/6206/s/xray-marker-with-scale/category/2582/
but I assume any known length might do for calibration.
OTOH, dental x-ray shows rather small structures so
the distance between the actual sensor surface and
the imaged body part could matter quite a bit.
Karsten
