Auxiliary lens screwed onto the front element — shortens minimum focus distance without internal adjustment. Essential for extreme close-ups and macro work.
If you suddenly realize on set that your lens can't focus close enough, you reach for a bonnette — a simple, but incredibly practical solution. You screw it onto your existing lens, and your minimum focusing distance is dramatically reduced. No need for a new macro lens, no modifications, no time wasted. The bonnette works like a magnifying glass: it bends the light so that your standard lens can capture details that would otherwise disappear into the blur.
In practice, you'll primarily need it for beauty shots, product photography, or when you need to capture details of props — jewelry, watches, textures. I use it regularly when the DP says, "We need extreme close-ups, but the focus ring isn't enough." A 4x or 8x bonnette (the numbers indicate the optical strength) sits in the case, costs little, and weighs nothing. Important: Quality varies enormously. Cheap versions create aberrations and color fringing — check your test shots on the monitor before you use them. Premium bonnettes (like those from Canon or Nikon for their professional lenses) are optically corrected and deliver on their promise.
The biggest advantage is flexibility. You don't need to change your lens, exposure remains stable, and autofocus still works in most cases. The disadvantage: with strong bonnettes (8x and higher), optical quality noticeably decreases, and depth of field becomes extremely shallow — you'll really need precise focus and a stable tripod. Vignetting can also be an issue with wide-angle lenses.
Combined with a follow focus or manual focus — especially for video — the bonnette becomes standard equipment for macro sequences. Some DPs have a weak set (2x/4x) placed in their lens case just in case close focusing needs to be unexpectedly tight. In a digital workflow, it's still faster than zooming in post-production or shifting in post.