There are numerous retro iPhone cases on the market, and most of them have no useful features except for helping you to stand out from the crowd. Holga, however, has introduced an iPhone case that not only adds some vintage flair to your smartphone, but also allows for photographic experimentation with nine built-in special effects filters.

Holga is a Chinese company known for its low-cost film cameras, that snap quirky distorted images. The unusual effect is appreciated by a number of professional photographers, even though it's certainly achievable using photo editing software. With the Holga iPhone Lens Filter Kit, it's now possible to play with lo-fi effects without a separate lo-fi camera.

Compatible with iPhone 4 and 4S, the case is available in red, blue, white, black or silver, and comes with a rotating wheel that resembles a rotary dial. There are ten different filters. Nine of them offer special effects, while the tenth, dubbed "empty hole," is a plain one that produces a simple hole effect. Filters are selected by rotating the wheel.

The choices offered include: dual, triple and quadruple image lenses that produce two, three, or four identical images combined in one picture (similar to Holga's split image filters); macro lens for taking pics as close as 6 cm (2.36 in); red filter with a heart shape in the center; red and green filters; as well as yellow or blue filters with a clear circular spot in the center. Examples are available in the gallery.

The Holga iPhone Lens Filter Kit is available online at a price of US$24.99, plus shipping.

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