From the PopPhoto Flash Archives

Something small, plastic and green can fix one photo problem: keeping horizons straight. A double axis bubble level, which slips into your camera flash hot shoe, keeps horizons straight and simplifies set-up. It’s just like hanging a picture, and the two-axis design means you can make sure your camera is set both horizontally and vertically. There are many levels out there, the one pictured here from Bogen/Manfrotto is $36, street.—Melissa MacateeContributing Blogger

Something small, plastic and green can fix one photo problem: keeping horizons straight. A double axis bubble level, which slips into your camera flash hot shoe, keeps horizons straight and simplifies set-up. It's just like hanging a picture, and the two-axis design means you can make sure your camera is set both horizontally and vertically. There are many levels out there, the one pictured here from Bogen/Manfrotto is $36, street.
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—Melissa Macatee
Contributing Blogger_