Fortunately for us, lights are like most technology-based products--they've been getting better and, in the case of headlights, mostly cheaper. The 600 lumens $120.00 Cateye that I use is self-contained, USB charged, will blast on high for a couple of hours and on low for about 3 1/2. Only a few years ago, that kind of performance would have put you at the high end of top brands like Light and Motion. It would have cost more like $500.00, the battery would have to go in a pocket, on the frame, or in a water bottle cage, would have weighed several pounds, and would likely require up to a 12 hour charge. Advanced LEDs have replaced HIDs and batteries just keep getting better, brighter, and lighter.
How much light do you need?
As usual, the answer is, "it depends....".
Lights-a-plenty to choose from in this display at Spokes.
Lights add a little cockpit clutter, but modern lights are compact and powerful. I've got a 600-lumen Cateye from Arkansas Cycling and Fitness on top of the bars and a small blinker below. Both employ USB charging.
This small light is plenty for being seen on the trail and in blink mode will enhance your visibility on the road.
While it is cool to light up the night, a bright light in the dark confines of the River Trail will blind anyone you encounter. You can fumble with dimming the light or simply shade it with your hand as you pass others.
A light on the bars and another on your helmet will allow you to light the road ahead while scanning through turns or lighting up the eyes of all those creatures of the night, of which there are many! This Black Diamond light is not made for the purpose, but an added Velcro band or zip tie will keep it in place on a bike helmet.
This seatpost-mounted Serfas tail light from Angry Dave's falls into the "obnoxiously bright" seizure-inducing realm. I need to hang a small blinker on my seat bag for trail and group ride use.
After dark, I suggest something in the 300-1000 lumen range, bar and/or helmet mounted. 300 lumens will be plenty of light to see the trail and to dodge wandering skunks, and 500-600 is plenty to light the way ahead. You can buy lights in that range for $100-150.00, probably less if you shop around.
With great power comes great responsibility.
It's easy to blind other riders, so be aware of the awesome power that you wield some of today's lights. I was finishing a ride recently at dusk; still plenty of light to navigate, but perhaps a blinker would be in order so others could see me. I encountered 3 riders, all of whom had flamethrower headlights, one of which was in some hyper-flash mode.
I was blinded for several yards and it wasn't even dark, yet! Please, dim those lights, boys.
This article mostly concerns road riding, as single track riders usually want all the light they haul. I also did not intend to get into the legal requirements for reflectors and/or lights. If you ride in traffic after dark, add every shred on visibility that you can manage. Reflective gear is often more visible to a motorist than your lights.
Even with all of that, I still follow the mantra of "ride like you're invisible", because to drivers, we usually are.
A call out to Chainwheel, J&P, Community Bicyclist, Riders Ready, and all the other fine shops that I didn't mention above. They'll all have what you need to make your transition to the dark side of the Fall Equinox.