Hi venkatabrahmahk,
You can use Photos or AirDrop to transfer your pictures onto your external hard drive from your iPhone:
Method A: Import via Photos (full quality guaranteed, and a lot more organized)
- Locate the Photos app (in the Applications folder), then open it while holding down the Option key.
- Release the key when a window appears asking you which photo library to open. Connect your external hard drive to your Mac, and click on the "Create New..." button. Then, click on the small down arrow next to the Name field, and navigate to your external hard drive. Select your external hard drive (or a folder inside your external HDD, if desired), then click OK.
- Connect your iPhone to your Mac via a Lightning cable (or use the included charging cable, which is a Lightning cable). Unlock your iPhone, and if prompted whether to trust the computer, select Trust. Enter your passcode if necessary.
- Your iPhone should appear in the sidebar on the left side of the Photos window. Select your iPhone, and all photos available to import should appear.
- Select the photos (and/or videos) you want to import, then click Import. Alternatively, to import everything from your iPhone, click on "Import All". If you wish to delete your chosen photos from your iPhone after the import is complete, check the box next to "Delete items".
- Once the import is complete, disconnect your iPhone. Then, quit Photos. Once the Photos app has quit, it is safe to eject your external hard drive.
- To open this library again in the future, do one of the following (after connecting your external hard drive):
- Navigate to where you saved the Photos library and double-click on it.
- Hold down the Option key as you open Photos. Then, locate the Photos library on your external hard drive.
Method B: AirDrop (Doesn't require a cable, but full quality isn't guaranteed)
- Verify that your Mac can send and receive from iOS devices over AirDrop by opening a Finder window and selecting AirDrop in the left sidebar. If you see the "Allow me to be discovered by" option, you're good to go. Click on "Allow me to be discovered by", then select either "Contacts only" or "Everyone".
- Clean out your downloads folder. This is where all of your photos will be arriving on your Mac.
- On your iPhone, open the Photos app. Locate your desired photos, then tap on Select.
- Select all of the photos you wish to send from your iPhone, then click on the sharing icon. (It looks like a box with an up arrow coming out of it.)
- Your Mac should appear in the AirDrop menu. Tap on your Mac, and if necessary, click "Accept" on your Mac.
- Wait for the transfer to complete. In the meanwhile, connect your external hard drive.
- Copy all of the photos in your Downloads folder onto your external hard drive.