How do I connect to 500px.com API ?

Based on abraham's TwitterOAuth library, pvr500px use rest api to connect via oauth 2

What return formats do extension support?

500px API currently returns data in JSON format. So we don't have a lot of choice :)

What kind of authentication is required ?

Applications must identify themselves to access any resource. 
If your application only needs read-only access and does authenticate the user, consumer_key containing a valid Consumer Key parameter should be specified in the query string. Otherwise, OAuth or upload keyauthentication takes care of identifying the application as well as the user accessing the API.

How to install this extension ?

Clone last source version from https://github.com/dspe/pvr500px. Copy it on extension folder.

Active extension, regenerate autoloads, purge cache.

Add datatype on your classes. Get customer key and customer secret from http://developers.500px.com/oauth_clients/new.