Today is Pancake Day. Whether you're going to spend your evening flipping bits of fried batter or not is neither here nor there because the kinds of pancakes we're interested in on Pocket-lint are ones you can strap to the front of your camera - pancake lenses, and if you don't know what a pancake lens is, then you're in the right place.

A pancake lens is a general term for short-barrelled camera lenses that have a very flat, thin shape making them lightweight and compact. They're used with DSLR cameras or hybrid models, like the Micro Four Thirds cameras from Olympus and Panasonic, and are favoured by shutterbugs who are looking for a relatively small camera with a pint-size lens system to match. The sweet moniker really only refers to the physical shape of the lens, rather than any special effects that they produce.

They tend to be be normal or slightly wide lenses, usually with a focal length of around 40-50mm, while the maximum aperture is generally about f/2.8, or slightly faster. They're also what's generally known as prime lenses, ie: that they are of a fixed focal length. So, there's no zooming in and out.

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Pancake lenses have been around for a while with Nikon's 45mm GN Nikkor lens being the best example from the 1960s, but the lenses really became popular in the 1980s, when they were used in compact SLR cameras. Supposedly, all of these more modern models were inspired by the original pancake lenses which made its debut in 1902 - the Zeiss Tessar.

Despite their diminutive dimensions, pancake lenses are said to offer very good performance, although users do report a slight loss of image quality, when compared with full-size prime lenses. Essentially, what you're looking at is a trade-off between picture quality and the convenience of a small lens. That and the fact that maximum aperture isn't at fast as you might like, with most pancake lenses offering a standard f/2.8.

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There are plenty of pancake lenses on offer today, with Panasonic's Lumix G 20mm f/1.7 lens being one of the most popular choices around thanks to its fairly wide angle 20mm focal length (equivalent to 40mm on a 35mm camera) and wide aperture, making it a good choice for taking snaps in low-lighting conditions.

Also popular is the 17mm f/2.8 pancake lens for the Olympus Pen E-P1 Micro Four Thirds camera and the Voigtlander lenses that can be used with Canon's DSLRs.

Do you use a pancake lens? If so, which one?