You need a different encryption program to do what you want.
For Windows, VeraCrypt is probably the best since it is free and quite solid. Setting up for use with a flash drive takes a little time, but will work very well.
If whole disk encryption is desired, you could use Microsoft’s BitLocker (if you have a Pro version of Windows) or Apple’s FireVault 2 (OS X). If you do not want whole disk encryption, you could format a flash drive to have more than one partition, and use VeraCrypt, Knox, BitLocker, or FireVault 2 to encrypt one parition, leaving the other for use without requiring secure access.
Some photo management software has built-in password protection and/or encryption capabilities. For example, iPhoto will save all photos as a single large file, and encrypting this one large file will protect all photos that are in that single library.
