Tuesday, December 1, 2009

Aperture and Digiscoping

Though digiscoping has opened the doors of nature photography to thousands of birders and other outdoor enthusiasts, it’s still not a silver bullet when it comes to obtaining good results. However, I do feel it’s a compliment to digiscoping whenever it is compared, albeit somewhat skeptically and critically, to high-end super-telephoto setups that cost thousands of dollars more. A common question is what effect will a smaller aperture scope have versus a large one when it comes to digiscoping.

Due to a typically large focal ratio (between aperture and focal length), spotting scopes are inherently optically slow even before you attach a camera. Light gathering is crucial when digiscoping. A small aperture spotting scope lets in less light, which directly results in slower shutter speeds, so if you’re unable to achieve a shutter speed of at least 1/125th of a second, it will be very difficult to freeze subtle movements of even a perched bird. Low shutter speeds often result in blurry images, one of the most common pitfalls facing both novice and seasoned digiscopers.

Less light being gathered also means a slight decrease in resolution, color, and contrast. Some of this can be fixed by post-processing your work with image editing software and tweaking things like contrast levels, brightness, and sharpness. While I’ve seen exceptional results taken with several of the high-end APO, HD, and ED 60mm to 66mm spotting scopes, I personally recommend 80 millimeters or greater for the best possible digiscoping results.

Smaller aperture spotting scopes exist for a good reason; they’re smaller and lighter in weight. Lugging around a large spotting scope and tripod can become burdensome on long hikes, and the relatively nominal lighter weight scopes do seem to make a difference for many individuals, especially those with neck or back problems. It essentially comes down to a question of priorities: are you going to place an emphasis on photography, or would carrying a lighter weight spotting scope benefit your outdoor excursions? It’s ultimately up to you, but now you know what the tradeoffs are to make a more informed decision before purchasing a scope.

Mike McDowell
Eagle Optics Staff

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