I have just bought a Sony Alpha 350, first Digital SLR camera. I want a zoom lens (18-70 came with it), help!!

Question

On ebay there is 2 zoom lenses (just want to play around cheaply before commiting to the Carl Zeiss etc) It says both are 500m, which would be great for airshows and safari park and balloon festival, but the length of them is so different, one is about 4 inches long, High Definition² Opteka 500mm f/8 Telephoto Mirror Lens, and the other is about 12 inches long High Definition² Opteka 500mm f/8 Telephoto Preset Lens. Both around £60, so affordable after just buying the camera, which one is better for my needs, or are they both the same? Thanks for any help

Answer 1

First, neither of the lenses you reference is a zoom lens. They are both fixed focal length lenses.

The mirror lens is a fixed aperture. In other words, the only control you have over exposure is your shutter speed. A mirror lens is light weight and easily hand-held.

The other 500mm lens is a traditional design telephoto and is much heavier and more suited to use with a tripod. It should have an f-stop range of f8 to f22 or maybe f32. By "preset" it means there is no connection between lens and camera to control the f-stop so you'll be using "stop down metering". In other words, if you use f11 the view through the lens will be dark which means it will be hard to focus even in bright sunlight.

The lens that came with your A350 is meter coupled - regardless of the f-stop chosen the diaphragm remains "wide open" until you release the shutter. So if you are using f11 on your 18-70mm zoom, the camera's meter calculates exposure at f11 even though the diaphragm appears to be wide open - very helpful for focusing in less than perfect light.

A much better choice of lens, IMO, would be the Minolta Maxxum 100-300mm f4.5/5.6 zoom. Yes, you can use the legacy Maxxum lenses on your Sony A350. I found a couple of 100-300mm zooms on eBay.

Item # 260265733486 has a "Buy It Now" price of $112.00 USD which looks like a steal.

Item # 120285833880 has 5 days 14 hours left and 1 bid - for $9.99 USD.

With a "crop factor" of 1.5, a 100-300mm lens will have the equivalent focal length of 150-450mm which should be more than sufficient for your needs.

IMO you should avoid the Opteka lenses and invest your money in the Minolta Maxxum zoom lens.