Does joining a large pool lower profits?

Hey guys i'm very new to mining and i'm hoping to upgrade to some good hardware soon. I've joined a rather large mining pool to ensure my efforts bear fruit. The thing i'm having trouble understanding is that if i'm in a large pool, does that mean that i wont make as much if i was in a smaller pool? The way i understand it is that in a pool you get paid for the % of work that you did in that round to get the block, but in a big pool wouldn't my % be much lower than in a smaller pool? I understand that large pools will get blocks much more often but it still is a bit confusing. Could anyone give me a hand an explain it a little better so i can figure if i should stick in this pool?

No, larger pools wont necessarily lower profits.

You are pretty much right with the % thing about being paid on the work you do in your pool. The larger pools generate way more blocks than the smaller pools, but have more miners to distribute it by.

In practice though, most pools work on PPS or PPLNS methods, which pays you based on shares, not the amount of blocks the pool makes. Just think of a share as a set of calculations that your computer does, and the pool pays you for that regardless of whether or not it actually helps solve that block.

However, the most important thing is the cut the pool takes. Some pools take around 9% and the best ones are around 4%. You just have to look around and find the best combination of pay per share (if doing PPS) and percentage cut that they take.

Hope that helped