Pictured below is a battery grip. You've probably seen one before, strapped to the bottom of a DSLR. It's big, bulky, and in the right situation, actually quite handy.
The function of a battery grip is in the name itself. It's an accessory that plugs into the bottom of your camera, providing room for an additional battery — and an extra hunk of plastic for the photographer to grip. Some grips are even called portrait grips, because they include a second shutter button that's more easily accessible while taking shots in portrait orientation.
These are nice-to-have features — but are they musts? And for the average shooter, what good can a battery grip do for you?
The photography community's relationship with the modest battery grip wavers between love and hate. Some feel that DSLRs are big and weighty enough as it is, and don't need the added bulk of an extra battery or grip. Others, having long embraced the grip, don't know how they could live without. Personal preference is clearly a big factor.
But there are other details to consider. Your average DSLR is ergonomically designed for comfortable landscape shooting — not portrait. Grips exist to make portrait shooting more comfortable by including a second shutter button on the side of the grip. When the camera is rotated, you can use that button to take portrait photos as you would a landscape shot.
Grips are also useful for those with longer or heavier lenses. Using a weighty lens on a relatively light DSLR can cause balance issues and hasten shooting fatigue. However, some suggest the added weight of a battery grip can act as a counterbalance, making it easier to maintain a steady shot.
That said, if you're travelling, or slinging a camera around your neck, a grip might not be the most practical accessory, as far as size and weight are concerned. But more importantly, that extra size might make it difficult to fit your camera in a bag or case.
Still, owning a grip is all about tradeoffs. The ability to add a secondary battery pack can be useful for extended shoots where recharging may not be possible, making the extra size and bulk worth it for some. And in a pinch, some battery grips even allow standard AA batteries to be used in the secondary slot. Good thing, too; extra batteries packs are sold separately, and not included with the grip.
This is a niche accessory, to be sure, but one with merit for a great many shooters. Would a battery grip be useful to you?