When people post into a community, their posts show up in the community feed. This makes it easier for those that are subscribed to the community's feed to see all of those posts to view or curate that content.
For your post to show up in the Photography Lovers community, you will need to make your post to the community by selecting it from the drop down menu after you have subscribed to the community from the main page.
I don't know of any posts that are specific for Professional photographers that would not allow blurry shots.
Thanks for the reply! Yesterday I wrote a post to the PL community but it didn't show up on my own profile. I guess I can write a post on my profile and then crosspost it into the community. At least I think so, I'll see.