External drives · Setting up your drive
How do I stop Photos opening every time I connect a camera card or drive?
Short answer: Open Image Capture with the card or camera connected, select it, and set "Connecting this … opens" to No application. Photos' import screen has a similar setting. Ordinary drives don't trigger it — only devices with camera folders.
It's a per-device setting in Image Capture. Open Image Capture with the card or camera connected, select it in the sidebar, and at the bottom set Connecting this … opens to No application. Photos also has a similar option in its import screen.
This only affects devices with photos (cameras, phones and memory cards with a camera folder); ordinary external drives don't open Photos.