The lock is not the problem
Secret Photo Album is better equipped than most of this category. Its listing describes a decoy PIN, a fake PIN, break-in alerts, Touch and Face ID, and an app lock after three incorrect attempts. On the lock screen it is doing more than its rivals.
The thing its own reviewers raise most often is not the lock. It is losing files. That failure mode belongs to the cloud-and-account half of the design, not the PIN half, which is why adding more lock features does not address it.
Where the files live, and who else has them
Secret Photo Album's premium tier offers cloud storage with access through your email address. That means a copy of your files exists on its infrastructure, reachable through an account.
Vaultine encrypts each file on the device with AES-256-GCM before storing it, and splits and randomises the stored data so nothing on disk resembles the original. There is no account, so there is nothing to be locked out of. If you turn on Dropbox backup, files are encrypted before upload, so Dropbox holds a blob it cannot read and we hold no keys either.
Hiding versus destroying
A decoy PIN shows someone a different set of files. Vaultine's Decoy Vault does the same and lets you choose in advance exactly what it holds.
The Duress Vault is the part that has no equivalent here. A third code opens an empty vault and wipes your real vaults as it does, for the situation where the files must not survive the next few minutes rather than simply stay out of view. Both are Pro features, and both are set up deliberately by you.
One vault, four platforms
Secret Photo Album is a phone app. Vaultine runs on Windows, macOS, iOS and Android, which matters if the documents you most want protected are the ones on your laptop.
