Are you talking about photos that you took and were saved directly to the external SD card, or photos that are currently in the Internal Storage?
Photos that are on your external SD card can definitely be transferred to your computer by Unmounting the card (in
Settings>Storage), removing it, then inserting it into your computer using the adapter. You can then copy or move those photos to your computer's drive using Windows Explorer.
Some devices have a camera app that allows you to select the external SD card as the default location to save photos. Open your Camera app, press the Menu button, select the Settings icon (looks like a gear or a bunch of switches), and look for an option for storage location.
If you have a number of photos already in the phone's Internal Storage, then you would need a good file manager app to copy or move them over to the external SD card, after which you could transfer them to your computer using the steps outlined above. Try something like
ES File Explorer.