Upgrading from kit lenses....

[Overread18 6]

When the camera auto-focuses the aperture blades on the lens are always wide open. This the AF sensors are always getting the full amount of light that the lens can deliver. The blades only close for the shutter so even if you select a very small aperture, the AF still gets the full wide open light to work with.

The motors in these lenses are also a lot better than in the lens you have now so you should find AF more of a use than you do at present - though subjects running head on to the camera is about the hardest for the camera to focus upon because of the constant need for it to keep resampling and changing the focus during the shooting. Here is certainly where a body like the 7D will stand out above the rebel you have now - however, as said, the lens is also very important because its got to have the AF motors to keep up.

Given the option of lens or body - go for the lens; all round it gives the most gain for your investment at this stage.

 

[jcskeeter]

I would maybe consider this: Sigma 70-200 f/2.8 as a different idea for a long lens. I demoed it at a cam shop and it seemed pretty solid. Not sure how it compares optically or if it matters for what you do. Build quality felt nice and it's got f/2.8 and OS (Sigma's IS equivalent.) For ~$1200 it's a nice piece of glass, I think. Then again I don't know how it performs in the real world though.

Anyone else wanna chime in on this glass? Seems like an option for the OP?? Or not? It's not Canon L glass but...

 

[DanPower]

Thanks Overread, I am definitely going with lens first.... a 7D with my current lenses wouldn't do any better than my 550

Your info on the autofocus is interesting, would the 70-200 f/2.8 focus faster than the f/4 version due to more light being available? This may be a reason to purchase the 2.8 over the f/4.... I might not use it at 2.8 much (at all?) but fast AF is one thing I want from my kit so it might be worth springing the extra coin..

 

[Overread18 6]

In good lighting I'm honestly not sure which would have the faster AF - remembering also that the f4 is much smaller so the motors have a lot less glass to move around inside. It's in poorer lighting where the differences would show up more, since the whole stop of light difference means that they've more to work with - not just meaning faster, but more being more accurate and less prone to hunting and losing a lock.

 

[DanPower]

the f4 is much smaller so the motors have a lot less glass to move around inside

Ahhh this is what I want to know.... is the 2.8's AF faster because of more light, or is the f/4 faster because of less weight? AF speed is definitely a big deal for me..

 

[Overread18 6]

the f4 is much smaller so the motors have a lot less glass to move around inside

Ahhh this is what I want to know.... is the 2.8's AF faster because of more light, or is the f/4 faster because of less weight? AF speed is definitely a big deal for me..

Remember the f4 might have less glass, but the motors will be smaller

Like I said I've honestly no idea was to which, in good light, can work the faster.

 

[joaopsr]

I would maybe consider this: Sigma 70-200 f/2.8 as a different idea for a long lens. I demoed it at a cam shop and it seemed pretty solid. Not sure how it compares optically or if it matters for what you do. Build quality felt nice and it's got f/2.8 and OS (Sigma's IS equivalent.) For ~$1200 it's a nice piece of glass, I think. Then again I don't know how it performs in the real world though.

Anyone else wanna chime in on this glass? Seems like an option for the OP?? Or not? It's not Canon L glass but...

Well, the Sigma is a nice and cheaper option than the canon.

The "regular" sigma f2.8 sells around the same price as the Canon f4 non-IS.
The "OS" version, sells around the price of a Canon f2.8 non-IS. This "OS" version has a completely new design, and is optically better than the standard version. Difference is not only on the stabilizer.

The problem here is the number of complaints you find on Sigma's "bad copies". A lot of users had to return them, and only after 2 or 3 replacements, the focusing came accurate. It's even more common on Canon-mount Sigmas.

But it sure is an option if you're on a tight budget.

 

[Dao]

As far as the AF speed. I honesty did not notice any difference between my 85mm f/1.8 and 70-200mm f/4L. Last time I use them at a circus event inside a stadium with poor lighting.

 

[rgregory1965]

I recently got the Sigma 70-200 OS and the Sigma 17-50 OS and bothe focus dead acurate first time out....extremely happy with both

EX lenses have 4 year Sigma warrantys

 

[DanPower]

Thanks guys, I'm also looking at the Sigmas, f/2.8 on the 70-200 for a little bit more than the Canon f/4L is attractive... won't be buying for a little while yet (minimum 3 or 4 weeks) so I still have some time to decide. I've pretty much settled on those two focal lengths so now it's just a case of whether I buy Canon or Sigma...

Whats the website where you can look at side-by-side test shots of different lenses? I've googled it to death but I can't find it.. it's not DxO there's another one...

thanks

 

[Dao]

You mean this one?


Canon EF 70-200mm f/4.0 L USM Lens Image Quality

 

[DanPower]

I do, that's the one I was thinking of. Couldn't find it no matter how hard I tried.

Thanks mate.