Right I’m vexed something rotten. I’ve decided that I need a new lens in the standard zoom length kind of area – currently got a 17-70mm 2.8-4.5 DC Sigma. It’s very good but the autofocus motor can’t keep up with the autofocus on the 7D. So new lens time. Narrowed it down to:

Canon 17-55 F2.8

or

Canon 15-85 3.5-5.6

Tried both in the shop, both have quick autofocus (point number 1 satisfied). Both weigh roughly the same (600g ish). More or less the same size…

The 2.8 is nice, but then I worry I’ll miss the extra length of the 15-85. Having compared the DOF of 55mm @ F2.8 vs the DOF of 85mm @ F5.6 is pretty much the same (at 20ft) so at the kind of distances i tend to shoot at they’d give the same about of subject isolation. Having also looked into the 7Ds autofocus, all the focus points are cross up to 5.6, so that doesn’t help… but i assume in theory the 2.8 should maintain focus easier in low light (i.e. UK MTBing in the trees). And it does give an extra 2 stops…

So which shall I get? Anyone acutally use the 17-55 for MTB photography?

From your choice I’d go for the 17-55 f2.8 for a light point of view and learn to use your legs to make up for the lack of focal length.
I generally use a 17-40L and am very happy with it.

Ah the 17-40, the other option…. Whats the autofocus speed like on it?

Didn’t throw in the 17-40 to confuse things. I use it on an EOS20d and focus speed is fine, positioning is more important. The only negative is the f4 which can work against it in dark environments.

The aperture advantage of the 2.8 isn’t going to be for shallow DoF for what you’re shooting, it’s going to be for night shooting (In My Neophyte Opinion). The -85 seems like a no-brainer to me in terms of how much of usage you’d get out of the difference; you might use the widest aperture occasionally, but you’ll be using the telephoto end of the lens all the time.

I don’t know what its AF performance is like, but if you really need a fast lens at that sort of range you can supplement the longer zoom lens with a nifty fifty for ~£80.

the 17-55 is a *MUCH* better lens than the 15-85

Unable to compare because I only have the 17-55mm, superb lens and can’t imagine you would be disappointed with it.
Not a bad idea to buy the hood, bit cheeky its not included given the price of the lens

The nifty fifty is a bag of pòo for the type of fast focus work the op want. The glass is awesome but the plastic body is poo and focussing is a hit or miss affair and waaaaaaaaaaaaay too slow.
I’ve never found the f2.8 wide open to be a significant problem, but it can be a problem.

17-55 is a superb lens, right up there with Canon’s ‘L’ series glass (only reason it’s not an ‘L’ lens is the fact it’s an EF-S mount and hence ‘not-pro’ 🙄 ). There’d be a difference in the image quality between the 17-55 and the 15-85mm, whether you’d notice it or not is another question… the 2 stops of aperture at the long end might be important to you, though with modern camera’s high ISO ability, maybe not… personally I always go for the fastest glass I can afford, so I have the 17-55 f2.8, my favourite lens (though closely rivalled by the 10-22mm 🙂 )

top tip with the 50mm is to use MF and pre-focus… superb lens for the money, great image quality!

I have a 50mm 1.8 sucks for anything moving (but is quite nice for stuff you’re not using Servo AF on). I could pre focus it, but then whats the point of having a 7D with bitchin fast AF if you’re going to do that….

Must say i’m leaning in the direction of the 17-55 (but then last week I was set on the 15-85). Would certainly buy the hood, it’s a joke that Canon don’t include it.

Not convinced there is much of a IQ difference between the two lens, I’ve looked at quite a few 100% photos and there is naff all in it. Both very sharp.

Cougar: You’re right I would use the 85mm end I guess, but then the 2.8 is more to provide lots of light for the AF tracking to do it’s thing. Just wonder if it’ll work very well at 5.6

NBT: you seem very certain…. care to share?

Latest edition of Photoplus has a very useful comparison review of all the better standard length zoom lenses

Have a guess which one wins, give you a clue its not the 15-85mm (they didn’t seem that impressed with it at all)

The updated model of the lens you are currently using did well, seems it now has a fast af motor and stabilisation too

NBT: you seem very certain…. care to share?

Sadly not through personal experience as I haven;t the cash to try either, just from reviews, and knowing what the canon model ranges are. My nephew’s a pro photographer in That London’s Famous London, when he was using crop sensors he swore by his 17-55. The only reason he sold it was the he went full frame all round.

Well I got the 17-55mm…. just need to find a form fitting case for it now so it doesn’t fill my camelbak unduly.

On the upside the autofocus with it is really quite spectaular…. not a great photo below, but I was tracking on Dan’s face and it’s pin sharp and he was shifting… (fair sized gap jump out of shot!)

IMG_7098.jpg by Ewan Panter, on Flickr

whats the point of having a 7D with bitchin fast AF if you’re going to do that

Most pros have more faster AF and don’t use it 🙂

Not only focal length but also the best set of F stops so your not reliant on flash
in amongst the trees or darker areas of the forest.
Me personally i would shoot like the pic above, have my widest F stop
which blurs the back ground and keeps your subject nice and sharp.

I’ll put it out there… Sigma 10-20mm and then a 50mm f1.8 for longer shots. Not ideal but 10mm is amazing!

08.01.2011 by Will – B, on Flickr

What camera are you using, will?
Good choice Ewan, colours look good from here. Now go and enjoy it. 😉

Most pros have more faster AF and don’t use it

Really?

Well I missed this earlier but I’d say that for action photography you want as much light as possible, and f2.0 is a lot more than f3.5 or f5.6.

So you already made the right choice I reckon 🙂

Ewan – Member

Really?

Dunno about “most” but a lot of Seb’s photo course was about pre-focussing and following the rider to get the pic you want in the place you want. Course is worth doing if you want to improve your pictures

http://sebrogers.typepad.com/seb_rogers_blog/2011/05/new-photo-course-dates-september-2011.html

Edit – oh and Mr Davis up there will be the elbow provider 🙂

Don simon – a 6 year old 400d 🙂 I love it!

Need off camera flashes too…..

Cheers will, Love the distortion a short lens gives, but damn, you were close… 😀