Moving Photos to External

Move the readable files,the other ones are either corrupted or in wrong file format. If they are corrupted,the only thing to do is probably to delete them,if it's some strange file format,search internet for file readers and converters that can convert them. In finder you can check the files to see file format,if it's any normal picture format like JPEG,TIFF,or any other of the most used ones,and the files still cannot be read,delete them.

 

Here's something that might help you identify the "unreadable" files:

You'll need CarbonCopyCloner.
It's FREE to download, and FREE to use for the first 30 days.
Get it here:
http://www.bombich.com/download.html

Now, you need to use CCC to "clone over" the photos to the external drive.
BE AWARE that you will have to "set up" CCC so that it will clone ONLY the photo files involved.
You can do this in CCC's window on the lower-left, by UN-checking things that you don't want copied.
There will be A LOT of things to un-check, but take the time to do it.

NOW...
Let CCC do the backup of the photo files.
As CCC copies the files, IF it encounters a "bad" or "un-copiable" file, it will make a note of it, and then continue on with the backup.
At the completion of the process, CCC should be able to present you with a list of those files that were not copied.

You can then use this to check the "bad" files, perhaps open them (on the original drive, if possible) and tweak them to a point where you can create a "new copy", etc.

WHY I suggest the above procedure:
As mentioned above, I believe CCC will IDENTIFY each un-copiable file.
BUT... if you do a simple "finder copy", the finder may tell you that "some files weren't copied", but WILL NOT "identify" them for you.

If you try this, let us know if it worked for you…

 

I'm going to assume the app you're using is iPhoto, is this correct?

If you have iPhoto open, to see the original photo that is displayed, try going to:
File menu --> Reveal in Finder --> Original

The "dirty little secret" of iPhoto and Photos is that they "store" the originals in their own "database", in which it's quite difficult to locate the actual files.

RIGHT CLICK on the iPhoto library file, and choose "Show Package Contents" to see where the actual files are stored.

I think the folder you're looking for is called "Masters", but again, GOOD LUCK in finding what you want in there, it's not "user-friendly".

Again, if you follow the advice I gave you in post 3 above, it will be much easier to identify WHICH files aren't getting copied over. I believe CCC can produce a log which names files that weren't "copy-able" and were passed over during the cloning process.
You can then make note of the file names, and use something like "EasyFind" to locate them.

You're not going to make much progress identifying them otherwise...

 

I believe the procedure as I outlined above will be the same for Photos as for iPhoto...