Looking for plugin requiring user to enter capture-able email to view gallery

I run an event venue and am looking for a way to have customers log in with their email address, which I can capture somehow, to view a gallery of weekend nightlife photos. I want them to be able to download the photos which I will have watermarked with my logo. The log in would not be something I give them, but rather their email address, which I want to put in my marketing platform, which is Constant Contact. For a password, I can use the date, any password I provide or they can set it up. I currently use NextGen Gallery plugin but am happy to switch. I am not a developer, but can manage a few things with direction. I have searched this forum for help, but cannot find anything that relates to my needs, hence the new topic. Thank you in advance for any help you can offer!