Hi @cpeters 
When I did FP16 with PyTorch Lightning in Kaggle kernels, the precision config was the only change I did to enable AMP. However, indeed, the dataset was 8bits images.
This time I’m running on a dataset that I created myself (using just a mobile camera). So possibly this is the reason of the issue.
Does it mean that I need to include bits downscaling into my data processing routine?
…just in case, I have posted a thread on the PyTorch Lightning side about this issue:

AMP: Native AMP doesn't work in my Gigabyte Aorus Master RTX 3070 environment · Discussion #7098 · PyTorchLightning/pytorch-lightning · GitHub 5

Thank you,
Roman