Backpacks distribute weight more evenly and naturally than a conventional camera bag: you'll not only be carrying the load with both shoulders, but much of it will be supported on the rear of your pelvis.
You'll also avoid a single strap's tendency to slip off your shoulders, which can be annoying at best, and a calamity at worst.
Huge backpacks for massive kit collections tend to be expensive, and have other drawbacks too. For example, they're often too large to take as carry-on luggage when flying.
Here, we look at sensibly priced options at about £100 or less. They're big enough to stow a lot of kit, but small enough to take anywhere, whether you're travelling by trains, planes or automobiles.
Which type of backpack?
Just how much camera kit do you have, and how much of it do you need when out and about? It's the first thing to consider when choosing a backpack, because designs fall into two main camps.
For a camera with several lenses and accessories, you're best off with a backpack that devotes its entire main compartment to photo gear. Good examples are the Lowepro Vertex 100 AW and Tamrac Expedition 6x. These have cavernous camera compartments with a wealth of adjustable dividers.
They're capable of accommodating one or two DSLRs (both with attached lenses) plus several other lenses, flashguns and photographic accessories. Once fully loaded, they should still be small enough to fit aeroplane carry-on criteria, but you'll need to keep an eye on the weight.
Some airlines are quite stingy with their carry-on weight allowance while others are much more relaxed, stipulating only that you must be able to lift the bag into an overhead compartment by yourself.
Growing hugely in popularity, the other option is to go for a split backpack, which has a smaller photo section (generally at the bottom) plus a separate compartment for stowing all your daily essentials.
They're great for a day out, but you'll typically need to limit the camera kit you take to a DSLR with attached lens, two or three other lenses and a flashgun.
Some backpacks, such as the Crumpler Cupcake, are available in both full photo and half photo options, to best suit your needs. We're reviewing the full photo bag in this group test.
When you're away for a day or two, a laptop computer comes in very handy and also makes the ideal tool for reviewing and editing your shots. Many airlines only allow one item of hand luggage and, even if you're just staying on dry land, it makes sense to keep all your valuable and fragile kit in one place.
All but three of the backpacks on test feature a separate laptop compartment. In most cases, this can accommodate a 15-inch laptop. Disappointingly, though, the specifications only generally allow for 15-inch laptops with an old-fashioned, 4:3 aspect ratio screen, so if you have one of the more popular 15.6-inch widescreen designs, it's not going to fit.
Front, back and sides
For hiking and climbing, it's useful to go for a design that features additional chest and waist straps for firmly securing the backpack to your body. Otherwise, the backpack can move around and catch you off-balance.
Either way, one of the frustrations of many photo backpacks is that you have to take them off your shoulders and lay them down on the ground in order to remove your camera. It's time consuming and the back of the backpack can get muddy in mucky conditions, right on the surface you wear on your back.
Some newer designs of backpack make life easier, with a side opening for access to your camera and attached lens. This makes access much quicker and you'll sometimes be able to easily grab your camera after just slipping off one of the shoulder straps.
Another idea, as featured on the Crumpler Cupcake Full and Manfrotto Veloce V backpacks, is that the main compartment unzips and opens at the rear of the bag, instead of on the front, so the surface that you wear remains uppermost when delving into the bag. It's neat for clean-freaks.
It's easy to think that if something won't fit in your backpack, you'll have to leave it behind. But it's often easy to attach bits of kit to the outside of the bag. For example, all the bags here but the Crumpler Cupcake and Tamrac Adventure 9 have fasteners for lashing a tripod to the outside of the bag, so you can carry one while still having both hands free.
The Manfrotto bag (as you might expect from a company that's famous primarily for tripods) features both internal and external tripod carrying facilities, plus a pocket for the tiny Manfrotto MP3-D01 camera support.
The Tamrac Expedition 6x really goes overboard with its MAS and SAS (Modular/Strap Accessory System) extras. The former enables you to fit large items such as lens pouches to the sides of the bag, while the latter is good for adding small pouches for mobile phones and so on to the straps.
Even without these add-ons you can often hook a pouch onto a bag strap, for a monster zoom lens or other accessory that won't fit inside. It's especially useful when you only occasionally want to take a big lens with you, instead of lugging around an extra-large bag all the time.