well, it depends on the "2 lenses" I suppose, but my favoured setup for carrying a camera on the bike is to use a "bar bag" with foam inserts - fine if the 2 lenses are a standard zoom and a wide angle or similar, not a lot of cop if you're trying to carry a 400MM f2.8...
I've an old Carradice Cotton Duck Barbag I've adapted, but if I was going for something new, I'd probably consider the Ortleib ones... Then google up a nearby foam-shop and get the inserts made to fit (or go pick-and-pluck if need be.)
Advantages of barbag are
1) weight's not on your back - that's a big deal if you're riding anything more than a hour or two - as most of my regular rides are.
2) camera's right in front of you if you want to stop and grab a picture.
3) the bags are on QR fittings, so you can easily detatch it, fit a strap, and carry it around like a conventional camera case.
but I suppose it all depends on what kind of cycling you're doing, what kind of bike you're riding, and what kind of distances/duration you're aiming for...
For me, the bar bag works great on a road or touring bike, with drop bars, and for rides of between a hour to 7-8 hours - or for extended cycle touring trips... Wouldn't dream of it on a MTB though - all that weight out over the front of the bike's bars really messes with steering on slower / more technical stuff... That's when a backpack would work better - but I don't really do that, and (strange as this may sound from a staff-member on here) I'd probably ask this question over on a MTB forum if I was looking for something to cope with off-road work (Singletrackworld springs to mind, you'd probably get Chipps (the editor of the magazine) giving advice himself, and he's been carting cameras around MTB routes for the past 20 years or so, and as "part of the industry" has probably had access to more kit than even the hardened TP classifieds fiends...)