Advice on a new telephoto lens for Canon rebel XT

[antoa315]

I have a Canon Rebel XT and I am looking to upgrade my current lenses. I have picked out a standard zoom lens, but I am having trouble deciding on a telephoto lens.

I currently have Tamron lenses that are about 2 1/2 years old and I find that the telephoto lens is too soft, especially at 300mm.

Just for some background, I generally use the telephoto lens to take pictures at conventions, so it's generally stage lighting and from a distance. I use a tripod, but sometimes there isn't enough room to really set it up properly. I've recently bought a monopod, but I haven't used it yet (I will have a chance to try it out this weekend). I am not a professional by any means and the problem could very well be with me and not the lenses.

I would like to keep my budget reasonable (the zoom lens I picked out is about $230 on amazon), but I don't want to end up with a lens where I don't see a marked improvement.

The two main lenses I am looking at are:

Sigma 70-300mm f/4-5.6 DG APO Macro Telephoto
Canon EF 75-300mm f/4-5.6 III USM Telephoto

And I am also considering (but hesitant because of the reduced zoom):

Canon EF-S 55-250mm f/4.0-5.6 IS Telephoto

In an ideal world I would love to buy (but it's about twice what I am wanting to pay):

Canon EF 70-300mm f/4-5.6 IS USM Lens

Anyway, I am just looking for some advice. Thanks.

 

[kobayashi]

I've bought a used 70-300 f/4-5.6 is few days ago, and it's great for outdoors on a sunny day. But when it's too cloudy or you are indoors, you will have problems.

When considering Sigma, keep in mind that it's a bit too soft at 200-300mm, but you can find one used for a half-price of the new one, so if quality is not an issue go for it.
Canon 55-250is is claimed by many that to be the best bang for the buck, although it has a modest aperture too, but at least it has IS and it's sharper than Sigma at 250mm.

The main problem is that with either of these lens it is very hard to make a good indoor photo at 200+mm due to way small aperture at longer focal lengths, except when there's a bunch of good lighting.

Today I made bunch of photos at some convention from around 30m, but lighting was good only for my 50/1.8, so had to go with ISO800 and even 1600 sometimes with 70-300, and still it was very hard to get shutter speed faster than 1/40-1/60 at 300mm. Photos are not of quality for a serious print, so it's better not to fiddle with camera in such situations if you cannot obtain acceptable quality (if quality is needed); if photos are only for you, than it's wasting money 'cause you'll only get dissapointed and wish you kept on saving more money for something better.

If you decide to go for 70-300is, keep in mind that it hasn't ring USM and that front element rotates, plus the front element extends and retracts a little even while only focusing - so getting it backwards to 70mm won't retract the front element completely - here you have to focus at infinity or switch to MF and focus manually to retract it completely.
But with 8-blade diaphragm it makes great bokeh for portraits and other close subjects (pigeons etc.), while IS is a nice add especially for zooming to 200-300mm when without it it's very hard to make a sharp photo. But, either way, it is not a good lens for indoor photography.

For that purpose, I'd consider 85/1.8 or 100/2, and if that is too short, keep in mind that there's nothing longer with enough wide aperture for less than 500$, that will give you even comparable quality.