Lots of cameras come with a zoom lens built into the camera. Prior to the digital camera revolution a zoom lens was an attachment to a camera body that produced a closer or magnified view of the subject. Film cameras of the SLR type (Single Lens Reflex) use interchangeable lenses with varied focal lengths. As you increase the focal length of the lens the magnification of the resulting image increases as well. Thus a 200mm lens provides a closer view than a 50mm lens. This closer view comes at a cost though. The 200mm lens will be four times larger than the 50mm lens and will weigh more as well.

Basic digital cameras provide two kinds of zoom options, optical and digital enhancement. When shooting the eclipse event it is best to avoid digital enlargements in the camera and strictly work with the optical zoom. In fact the best way to treat digital cameras is to turn off all the extra digital enhancements when obtaining the images. There will be plenty of time for that sort of work after the eclipse.

Digital SLR cameras accept multiple lens configurations however they may have a film plane smaller than a film SLR. A typical digital SLR has a chip where the film would go. That chip will vary in size. Most digital SLR manufacturers provide a multiplier that can be applied when using a lens. That multiplier indicates the relative size of the imaging chip. The popular Canon Rebel has a multiplier of 1.6x. This factor is applied to the lens focal length (a 100mm lens acts like a 160mm lens). The 1.6x factor is the result of the imaging chip being roughly 5/8ths of the size of 35mm film.

Great images can be obtained using lenses with a focal length of 100mm and greater.

70mm	300mm

The use of teleconverters or lens multipliers is not recommended most of the time. Unless you are using a high grade, low reflection, lens enhancement it is recommended that the extra lens not be inserted. The result of using such a lens enhancement is often extra reflections in the image showing up as blurs. Test the system by taking exposures of the young or very old moon (thin crescant phase) and over exposing the image to reveal the Earth shine. Look for blurry areas in the picture, those are the result of internal reflections in most cases.