Sport Shooting w/ teleconverter

I have been reading all the great information on this forum for sometime now. I'am just a noob so bear with me, I have an XTi with a tamron 28-300 lens and I'am thinking about adding a teleconverter for taking pictures of my son's sports activities, some times I'd just like to be closer so I'am thinking about a 1.4 teleconverter. Will my pictures suffer tremendosley like I've been told by the local camera store, and is the Canon brand teleconverter neccessay?
Thanks in advance for your advise.

Generalizations...

1.4 convertor often exhibits little to no signficant loss of quality; 2x normally does!

The results may be better for a given lens than another one! (e.g. you might not see loss of quality on 1.4x with Canon 70-200L, but you might see something bad with some bargain you bought from Walmart (disclaimer--I use them only for illustration, not to say their products are not good!!!). Lens flaws are magnified with the convertor.

Many users report that optical results with other brands of convertors are not distinguishable from Canon's.

Keep in mind that your XTi has a minimum requirement for max aperture in order to retain autofocus. You might be defeating the AF capability by adding the 1.4x to your lens.

i would like to suggest against a tc and superzoom lens. your xt will not focus if you use a decent tc, and even if it could, it would be very hard to get the focus on the right spot. as far as i know, no activities require more than 300mm to get a decent shot. soccer, football, ALL indoor sports, track and field, even paintball are shot within the 300mm mark (ok, football and soccer do see longer lenses, but mainly when you're making enough money off of it to justify using that much money..)

go find out if you can get in closer (sideline access, field access, etc) instead. you'll not only save money, but also end up getting much better photos.

shelglass wrote in post #2400417
I have been reading all the great information on this forum for sometime now. I'am just a noob so bear with me, I have an XTi with a tamron 28-300 lens and I'am thinking about adding a teleconverter for taking pictures of my son's sports activities, some times I'd just like to be closer so I'am thinking about a 1.4 teleconverter. Will my pictures suffer tremendosley like I've been told by the local camera store, and is the Canon brand teleconverter neccessay?
Thanks in advance for your advise.

I really doubt you can use a TC on that lens. The problem is the short end - it's going to cause problems with fitting. You're probably going to have to buy another zoom. What's your budget and what sports (indoor/outdoor)?

shelglass wrote in post #2400417
I have been reading all the great information on this forum for sometime now. I'am just a noob so bear with me, I have an XTi with a tamron 28-300 lens and I'am thinking about adding a teleconverter for taking pictures of my son's sports activities, some times I'd just like to be closer so I'am thinking about a 1.4 teleconverter. Will my pictures suffer tremendosley like I've been told by the local camera store, and is the Canon brand teleconverter neccessay?
Thanks in advance for your advise.

Here's the problem other's started to explain but didn't elaborate enough about. The problem is light. The lens you speak of has a max aperture of F/6.3 at the far end of its zoom range (which for sports photography is probably where you'll spend most of your time).

Canon only rates their bodies as being able to autofocus at f/5.6 and faster (lower number). Now, f/6.3 on a sunny day will be just enough light for your lens to focus (despite it not being within Canon's range) which is why you're able to use it now, but when you add the 1.4 teleconverter, you're going to be losing an additional stop of light which WILL definitely render your autofocus useless.

On top of that, your lens with the teleconverter on and zoomed all the way out, will pass so little light, you could run ISO 1600 and STILL get very slow shutter speeds.

Unfortunately, there is little you can do about this except to find a more dedicated sports lens. You can pick up the Sigma 70-200 F/2.8 (much much much faster lens than what you're trying to use now) for about $900. That's a LOT of money, but you're attempting to enter the one subset of photography where money is a necessity, not an option. You can get away with a $79 lens for portraiture. You can get away with the kit lens for landscapes. You may not get the most technically perfect pictures, but you won't lose the shots either.

Now sports ... sports is a completely different beast. You need speed for sports, and ask any racer ... it takes money to go fast.

Bill

or choose a used 70-200 f/4 for $475 used in A+ condition

I was thinking along those lines of faster lens 200mm f2.8, because when I used the tameron 28-300 lens on my previous camera, sharpness was a problem zoomed at 300. So i think it might be time to sell some of my other toys and invest in some nice glass that works for shooting sports. There is something about shooting zoom esp. of my kids playing sports, very....cool.