E145 CAPTAIN ASSUMES CONTROL ON ILS INTERCEPT WHEN FO DELAYS ON-COURSE TURN. TCAS TRAFFIC WARNING OCCURS FOR TRAFFIC ON PARALLEL RWY.

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WE WERE CLRED FOR THE VISUAL APCH TO RWY 28 INTO ATLANTA. THE FO WAS FLYING AND HE ARMED THE APCH. HE WAS INTERCEPTING THE FINAL COURSE ABOUT 5 MI OUTSIDE OF THE FAF WITH ABOUT A 20 DEG INTERCEPT ANGLE (WE WERE HEADING ABOUT 300 DEGS TO INTERCEPT) WHILE SLOWING THE AIRPLANE. WHILE THE FO HAD ARMED THE APCH; HE HAD A COMBINATION OF SPD AND INTERCEPT ANGLE THAT WAS TOO GREAT FOR THE AUTOPLT. I STATED HE NEEDED TO START TURNING. VERY SHORTLY THEREAFTER (A FEW SECONDS); I REALIZED WE WERE GOING TO OVERSHOOT THE FINAL COURSE; SO I IMMEDIATELY TOOK THE FLT CTLS AND INITIATED A 45 DEG BANK ANGLE TURN TO THE L TO RETURN THE AIRPLANE TO THE FINAL APCH COURSE. AS WE WERE IN THE TURN; THE TCAS STATED 'TFC; TFC' (ONCE) AS THERE WAS AN MD80 ON APCH TO RWY 27L. I DO NOT BELIEVE WE WENT FULL SCALE OFF TO THE R OF COURSE; BUT I AM NOT SURE AS I WAS HAND FLYING A STEEP BANKED TURN AT THE TIME. NEITHER ATC NOR THE OTHER ACFT MADE ANY COMMENT; AND THERE WAS NO RA. I RETURNED THE CTLS TO THE FO AND THE REST OF THE APCH WAS UNEVENTFUL. ROOT CAUSE WAS THE INEXPERIENCE OF THE FO WITH VISUAL APCHS. I COULD HAVE ALSO TAKEN THE CTLS SOONER; HOWEVER; I BELIEVE THAT SEPARATION WAS NOT COMPROMISED AND WE WERE IN VISUAL CONDITIONS.