CalcLockAt a glance: A Shared Album is a way to exchange pictures, not proof that you have the original capture. Identify the contributor and the version you need before importing.
Ask what you are trying to preserve
A family album may contain the only version of a picture you can currently see. That makes it valuable, but it does not automatically make it the original file. Perhaps you want a pleasant image to view privately. Perhaps you need enough detail for a large print or the full video for an archive. Those are different requirements.
Write down the intended use first. For a viewing copy, the shared image may be sufficient. For future editing or printing, it is worth finding out whether the person who took it still has the source.
Check the album type and source
Do not confuse Shared Albums with an iCloud Shared Photo Library. They are different Apple features. Apple's current Shared Albums documentation describes version-dependent behavior and limits; older shared-album workflows can reduce photo dimensions and video resolution. Read the guidance applicable to the software used for your album rather than assuming that every shared file is unchanged.
Look for the contributor, capture date, and visible details. If the image is important, ask the contributor for an original-quality copy through a method you both consider appropriate. Do not forward somebody else's private image merely to test a transfer.
Save and inspect a source copy first
Use Photos to save the item from the Shared Album into your own library when permitted. Open that saved copy, not just the album preview. Zoom into faces or lettering and play videos from start to finish. If you have another version, compare them side by side before deciding which one to import.
Give special attention to panoramas, small text, and scenes you might crop later. A picture that looks crisp as a thumbnail may not retain enough detail for those purposes. Encryption cannot recreate detail that was absent from the file supplied to the app.
Import one version, with a clear purpose
For CalcLock, choose the collection intended for this material, enter its exact expression, and press equals twice consecutively. Import a small selection from the saved sources. Inspect the imported result and retain the source files. If you later obtain a better original, compare it before adding another copy so you do not confuse the two versions.
CalcLock has no export or sharing feature. It is therefore unsuitable as the only staging place for photographs you will later send to relatives or a printer. Keep a separate usable copy for those tasks and protect that copy appropriately.
Do not mistake importing for withdrawing access
Importing a shared photo does not revoke anybody else's access to the album or remove copies they already saved. Conversely, the album owner changing or deleting an album can affect what you can access there. Your plan should not depend on a shared collection remaining available forever.
A local vault and a family sharing arrangement solve different problems. CalcLock does not synchronize the album, notify you when its contents change, or recover a lost collection from an account. Preserve any important source independently, and discuss sharing changes with the people involved rather than treating an import as a privacy reset.
Questions, answered
Will a vault improve a compressed shared photo?
No. Storing a file privately cannot reconstruct missing resolution or turn a shared derivative back into the original capture. Seek the source file when those details matter.