Energy is not perception

The energy here is the energy of the uncentered tensor, so a bright background can dominate it — it can account for most of the squared energy while the small details that matter to recognition carry very little.

Retained energy is not a guarantee of perception, and not a guarantee of downstream accuracy. A small but important feature can vanish while a 95% or even 99% energy test still passes.

So choose a rank with three separate pieces of evidence: energy, visual fidelity and storage. Reconstruction energy alone cannot validate a CNN task.