After photo transfer: check your backup copies
Keep original camera files, make a separate copy and check the files before making storage decisions. Includes a tested macOS checksum example.
- File transfer and backup
Seeing a thumbnail after transfer does not establish that every original file was copied successfully. Before you clear a camera card or remove an existing archive, make another copy and check what it contains. This guide explains a limited file-checking method; it does not test every camera, phone, cloud service or future restore.
Keep the original set
Finish the transfer using the exact camera or lab instructions. Leave the original files where they are while you inspect the new copy. Film scans should be downloaded as delivered files rather than screenshots of a lab gallery. Give the receiving folder a useful name, such as a date and roll or outing reference.
Check the visible result
Compare the expected file count and open several files, including pictures from the beginning and end of the set. Look at full images rather than only generated thumbnails. A successful file count is useful, but it cannot establish whether a file already contained damaged image data before transfer.
Make a genuinely separate copy
Copy the complete folder to a separate storage location you control and can access again. Two folders on the same drive share that drive's failure risk. A synchronized folder can also copy a deletion, so understand the service's version and deletion behavior rather than assuming synchronization is a complete backup. This article does not guarantee recovery from every loss.
A checked macOS file example
On macOS, the built-in shasum command can calculate a SHA-256 checksum for a file. In Terminal, type shasum -a 256 with a space at the end, drag the file into the Terminal window to insert its path, and press Return. Repeat with the corresponding file in the second location. Compare the complete 64-character checksum, not the path text.
shasum -a 256 photo.jpg
shasum -a 256 copy/photo.jpgThe short paths above are examples for a folder containing photo.jpg and copy/photo.jpg. Use your actual file paths, or drag each file into Terminal as described above. This command reads files and prints checksums. It does not copy, upload, delete or repair them. Matching SHA-256 values support byte equality for the two files checked. They do not prove every file was included, image quality, a different drive's health or future availability.
What we actually checked
We ran this command on macOS with clearly synthetic local files, copied them into two separate test directories and confirmed matching checksums. Changing one test copy produced a mismatch. These were software fixtures, not customer pictures, a physical backup-drive test or a successful disaster recovery. The exact check date was October 30, 2026.
Keep your storage decision separate
Keep the originals until you have checked the complete set and the separate copy. This guide does not instruct you to format a card or delete files. If you are unsure, keep the source and follow the exact device or service instructions. A file-copy check is one part of a backup process, not permission to erase the only remaining original.