no detection on clearly tag

[Liufarhigh]

There may no detection when camera shooting with backlight, even the tag looks very clear. Is there any threshold adjustment i can do?

[brmarkus]

With only one instead of two tags be detected?
Will both be detected with more space between them?

[Liufarhigh]

neither of tags be detected when camera shooting with backlight , when blocking the light behind tags, both tags can be detected, that's why in photo2 I put some blocking behind tags

[brmarkus]

Is your camera moving, are the tags moving or stable and stationary?
Could you apply a mask (of stationary, not moving, known coordinates, or preprocessing to find the bright rectangle, or using a neural-network and doing object-detection and then apply a mask)?
Depending on your camera model you might be able to use white-balancing. Or using computer-vision to do white balancing.

[Liufarhigh]

will white-balancing help? in my use case, camera is moving, and i'm avoiding using deep learning method

[brmarkus]

Can the lightning vary a lot in your use-case, so you need to react dynamically or is it the same all the time when your camera moves around?

White-balancing is just one idea of many using computer vision to pre- and post-process images.

You could use a metric to adapt saturation/brightness/white-balancing/grey-scale-conversion/black-white-thresholding/gamma depending on the spectrum of a captured frame (each frame or every 10th frame, etc.).

Use a few captured frames, store them, and experiment using a picture editor to see what could make the tag detection reliable again.

Could you add a filter to your camera(-lense)?