They're not universal!
I cannot use a Canon mount lens - or Nikon, or Pentax, or Olympus, etc. - on my Konica Minolta cameras. I can use a Sony lens on my cameras because Sony adopted the KM "alpha" lens mount system. [Similarly, Panasonic has adopted the Olympus "four thirds mount," Samsung cameras use the Pentax mount, and Fugi cameras use the Nikon mount.]

Also, older manual focus lenses are usually not compatible with modern autofocus cameras. So when you buy lenses make sure that you are buying an AF lens in the correct mount.
 

Third party lenses are often cheaper and sometimes better!

Sigma, Tamron and Tokina lenses are good reliable choices. Usually you can get a particular lens manufactured by these companies in a variety of lens mounts. [You can get virtually any of there lenses in Canon and Nikon mounts, and usually in the other mounts as well.]

Vivitar also makes (or made) some good lenses. They are identified by the "Series 1" label. These lenses were actually manufactured by other companies - mostly Sigma - and can be great bargains. I would steer clear of non Series 1 Vivitars and their clones with names like Phoenix and Promaster. On the other hand these lenses are cheap and may be just the ticket for a lens range that you won't use often. Just remember that you usually get what you pay for!
 

All manufacturers have different grades of lenses.

A Sigma 70-300 APO lens, one of the most widely recommended for baseball photography, is not the same as a Sigma 70-300 Super II lenses. The APO is top of the line. It's also about $60 more expensive, but worth it.

Do a little research to make sure you know exactly what you are buying. A great source for information is a user forum. I recommend those on Digital Photography Review (www.dpreview.com). When in doubt ask the people who are using your camera on these forums. That is a great resource! Just be specific about what you are looking to shoot and how much you are willing to pay.
 

Buy fast glass!

By fast I mean lenses with the largest possible aperture. This corresponds to the smallest F-stop number. For example, my Sigma 24-135 f3.5-4.5 is considerably faster than my Sigma 29-105 f3.8-5.6. That means I can use a larger aperture and admit more light to the picture sensor, allowing me to get pictures I couldn't get in low light with the slower lens. It also means I have greater control over the depth of field.

The gotcha is that fast glass is expensive. You may be able to find a 70-210 mm zoom (a great range for anything in baseball except for the outfield) for $75 at f4-5.6 whereas a f2.8 in the same range is $1125!
 

Pick the right focal length.

If you are standing on the home plate side of a dugout and shooting a batter, you need something in the range of 50-75 mm. If you are trying to shoot the outfield from the same location you need at least 400 mm. Standing past the dugout shooting the near outfield you'll get good shots from a 200-300 mm lens, but you'd prefer 400-500 mm to get center field or the opposite field.

Understand, please, that I'm assuming you are shooting with a digital SLR camera with an APS-C sized sensor. Because these sensors are about 24mm in size there is a 1.5 magnification factor compared to shooting with a 35mm film camera. [The Canon sensors are slightly smaller and have a 1.6 magnification factor. The Olympus/Panasonic camera sensors are smaller still and have a 2.0 magnification factor. Be careful, though, because smaller sensors mean higher noise. You'll see that on the Olympus.]

Since you don't want to be changing lenses every time you shoot a different field position, you'll need at least one telephoto zoom. Ideally you could pick up the Sigma 50-500 f4-6.3. That will cover everything very nicely. But guess why it's called the "Bigma." You can forget about using this baby without a tripod unless you are shooting with a Konica-Minolta, Sony, or Pentax camera with in-body stabilization. [Even then you may need a tripod at 500 mm.] Plus it's about $1,000 (worth it, though).

Most of us will compromise and the budget/speed sweet spot is probably with the 70-300 mm telephoto zooms. Although I use a 75-300 mm Minolta lens, I generally recommend the 70-300 mm Sigma APO lens because it is available in virtually all mounts and is highly recommend - a bargain at about $200.

If your son is an outfielder consider the Bigma or a Vivitar 100-400 mm Series 1 (which you should be able to find, given some patience, on E-bay for about $100-200). [Note that this is less critical if you are shooting with a larger resolution camera such as one of the new 10 MP DSLRs. You can crop your shot on your computer and still have plenty of pixels for a large print.]
 

Save money by buying online!

I hate to admit it, but I have well over $3,000 invested in camera equipment in the last year. [You don't have to do this; I'm addicted.] I've never actually bought anything except a filter and lens cleaning materials in a bricks-and-mortar store. However, I did purchase my first DSLR body from Circuit City. I did it online at circuitcity.com. I paid $615 for a KM 5D kit and picked it up 30 minutes later at the Willowbrook store. The same kit on the shelf at that store was $759.

Price is the advantage to buying online. You can generally find everything a little cheaper from a reputable online vendor, and you don't have to pay sales tax unless the vendor has a physical presence in Texas (as with Circuit City). You do have to pay shipping, but that is usually a lot less than sales tax for relatively light stuff such as photographic equipment.

Be careful, though, as some online vendors have very poor reputations. When in doubt check out the vendor's reputation at www.resellerratings.com. I have had very good experiences at the following sites (in addition to www.circuitcity.com) and I recommend them:

• www.amazon.com (always check here before you buy)

• www.bhphoto.com

• www.adorama.com

• www.tristatecamera.com

• www.cametacamera.com
   

Don't forget E-bay!

E-bay is just plain fun! And you'll find some good deals. But you have to (1) know exactly what you want, (2) know exactly what you're bidding on, and (3) research the seller - there are some shysters! I wouldn't buy from an E-bay seller who didn't have at least a 95% positive rating.

Cameta Cameras, mentioned above, is mostly an E-bay seller. They have a storefront in NY and their own Website, but when you buy it's via E-bay.

I haven't had a negative E-bay experience. I have purchased six lenses, a flash, a remote cable, and a battery from E-bay. No problems. But I have heard some horror stories, so be careful!