Sony makes a few different telephoto zoom lenses, all very similar. The $300 SAL-75300 is probably the most common. Te aperture is on the slow side, f/4.5-5.6, but that is typical of budget lenses. It basically means it will only be useful in daylight. If you need a lens for low light (which is anything that is not strong daylight), then the cost goes up significantly. Sony's SAL-70200G isn't as long as the 75300, but it has much brighter optics and a faster focusing motor...and a $2000 price tag.