Casa Mila/La Pedrera Camera

Just from reading the same rules, I would change plans if I could not leave my camera in a locker,
But your camera also looks compact enough it might fit in a cargo pants pocket or a small bag that you can just carry with you.
They just don't want you sneaking to take pictures

I'm not familiar with the size of your camera, but in January of 2017, we went to Casa Mila and my daughter had a Nikon camera with multiple lenses and it was never an issue. She carried the camera and 2 lenses in her cross body purse. When I think of professional camera gear, I'm thinking more of a camera bag/backpack that someone opens up and is changing lenses and filters and maybe even using a tripod. It does get rather crowded so someone messing with multiple camera "attachments" would hinder the traffic flow. Perhaps you can try to email Casa Mila and ask them to address your question. When I do this, most places, surprisingly, respond.

Photography was allowed at Casa Mila

What is not allowed is a professional photographer who will most likely make a profit of his/her work taking pictures inside La Pedrera -even if you're on holiday. So... anyone "resembling" a professional photographer -and your gear will give you up!- when entering the premises will be asked to produce an authorization from their Press Department, or to leave the camera in the lockers downstairs. Sounds very logical to me :)

Having said that, your particular camera doesn't necessarily strike me as a signal of paparazzo :)), so, if you're not stuffed with a lot of extra gadgets, I don't see why you shouldn't be allowed in with it. You can always write them and ask for clarification: http://www.lapedrera.com/en/plan-your-visit/visitor-regulation

PS: I do seem to recall the lockers are "manned" so anything you leave is secure.

The ban is on professional photography - not cameras.

I just googled your camera and it doesn't appear to be in any form "professional" to me. My husband had no problems going in and using his camera, a Canon 5D Mark III, with multiple lenses in full sight of the staff. No flash and not tripod, of course. That was 2 weeks ago.