I don't know much about daypacks but I've been eyeing the new packs by Simms. They're pretty nice and may suit my needs just fine. If you are really concerned about your DSLR I think Simm's also makes some waterproof backpacks that you might consider.
i like my backpacks to have an internal frame because of my back so i like the Gregory z35r but my dad loves his Osprey talon 22 that doesnt have an internal frame, they also make some smaller sizes in the Osprey.
I've tried several lightweight, medium-capacity (~30L) packs for 'day' use. For me that means a 5-10 mile weekend hike with the dog and bringing along lunch, water, dog snacks, rain gear, GPS, trekking poles, camera, and sometimes, my heavy Manfrotto tripod. So far the best I've found is the Deuter Futura 32BC (http://www.rei.com/product/797596) for about $130.
First and foremost is the suspension system. The Deuter simply fits better than any other pack I've yet tried, including several larger ones at 3 or 4 times the price. That doesn't mean it'll necessarily fit you as well as it does me, but it seems like a pretty good reason to start with that model. The spring-steel side stays support a taut mesh back panel that provides outstanding ventilation on even the hottest days.
Second, the pack has an optional zip-up divider in the main pocket which, together with the lower zip-up outside access panel, means you can effectively convert the main bag into a 2/1 configuration to keep lighter gear like clothing at the bottom where it'll provide cushioning for you camera gear in the upper two-thirds. At 32 liters (~2,000 cubic inches), it's large enough for a 2-season ultralight overnighter.
Third, the pack has a waterproof stowaway rain cover that fits neatly in a bottom pocket, ready to break out and cover the pack to protect the contents from a downpour.
Finally, it's got a better-than-average array of external zip pockets, compression straps, mesh water bottle pockets and lash points along with an internal hydration sleeve to fit your Camelback or other water bladder.
In fairness, at 3 lbs 10 oz it's actually heavier than the 60 liter REI Flash 60 I just bought for weekend trips. But the REI pack lacks many of the creature comforts of the Deuter making it seem Spartan by comparison.
i use the older (blue) simms dry day pack for everything
in the last year i have been to mexico city ,northern england and paris
not only does iit keep the laptop and nikon dry it also seems rather safe from pick pockets
one can't just unzip it in a crowded subway
then when i fill it with clams at a local beach i can hike out the 2 miles w/o it dripping on me
it is small enough to fish with
and as i usually fish to long into the rising tideall my gear stays dry as i wade up to my pits to get around a fallen log
the newr generation of green simms bags look sweet
good luck and have fun chasing fish over here
just don't expect many rezzies
I used to do a considerable amount of hiking and backpacking with an SLR, lenses, etc. I got tired of having to stop, remove the backpack, and unpack whatever I needed for the photo(s), so I went with a Lowepro Toploader Case with a chest harness. The Toploader & chest harness went on first, then the backpack. The camera was always available for quick shots on the trail, and immediate photos of wildlife, etc. I found that I took a lot more photos with this set-up since I could access the camera very quickly when needed.