B737-800
Air Traffic Control Fully Certified
Situational Awareness
ATC Issue All Types
Air Traffic Control Issued New Clearance
Human Factors
ORD was on West Flow triple Simultaneous approaches and I was working the North Runway 27R; visuals. It was hazy and somewhat difficult to see the airport but everyone was seeing the traffic to follow. I turned Aircraft X base and descended to 30 and told him to report the field or the traffic in sight. His reply was 'Too hazy to see the field and to way much traffic to call in sight' so I turned [him] left to a 060 heading and climbed to 40 to go out for the instrument approach. I lost separation with Aircraft Y on the ILS to 27L when I turned Aircraft X to the left. It was a complex situation running visuals because the pilots had to see the traffic they were following and really couldn't make out the airport because of the haze. It was very labor intensive to run visuals like this and is much more efficient for the user; however I should've went out for the ILS sooner. My biggest mistake was turning Aircraft X to the left instead of turning to the right. I thought I had enough time to make the turn as Aircraft X was slow and I wanted to save him some miles. Had I turned right I wouldn't have lost separation but the aircraft would've had to fly a couple miles further. Next time I'll go right!
C90 Controller described a loss of separation event during simultaneous approach procedures and hazy weather conditions making sighting traffic and the airport difficult for the flight crews.