Pot is too small to call down right?

[C-Dog]

Villain is a loose passive player, AF below 1


Party Poker 1/2 Hold'em (6 max, 5 handed) converter (http://www.selachian.com/tools/bisonconverter/hhconverter.cgi)

Preflop: Hero is Button with 7/images/graemlins/diamond.gif, 7/images/graemlins/club.gif.
<font color="#666666">1 fold</font>, MP calls, <font color="#CC3333">Hero raises</font>, <font color="#666666">2 folds</font>, MP calls.

Flop: (5.50 SB) 4/images/graemlins/diamond.gif, 3/images/graemlins/heart.gif, T/images/graemlins/diamond.gif <font color="#0000FF">(2 players)</font>
MP checks, <font color="#CC3333">Hero bets</font>, MP calls.

Turn: (3.75 BB) 5/images/graemlins/diamond.gif <font color="#0000FF">(2 players)</font>
<font color="#CC3333">MP bets</font>, Hero folds.

Final Pot: 4.75 BB

[w_alloy]

This is tough without reads, and theres a huge difference between an AF of .4 and .9, AND i've never played 1/2, but I think if its closer to the latter af number theres a good chance he has a 5, a high diamond, or (rarely) even a 6 or 2 for the oesd. Remember this card looks like it is unlikely to help you, but it very well might help him, and thus he may also bet random hands. If you're behind, theres a good chance you still have 6 outs. The pot isnt that small, you need to be right about a third of the time on a calldown or free card play.

If his AF is say over .7, depending on how loose he is, I raise folding to any more aggresion and check behind ui on the river.

If its any lower I fold. I might be giving this guy too much semibluffing credit especially since its 1/2... maybe .9 should be the AF cut off without reads (I know how arbitrary this is but its close and you gotta draw the line somewhere).

Reworded some points on edit.

[aK13]

Fold. Even against an unknown you need to be sure he's bluffing about 33% of the time to justify a calldown. I don't see it being nearly that frequently, especially since you say he's a passive player (however, there are some bluff-happy passive players...)