I've been using a Canon 400D for a couple of years, mainly with a Sigma 17-70 f2.8 lens. I've also got a Canon 50mm prime, which takes far better (Sharper, crisper) images, but is nowhere near as versitile.
I know it's easier to get prime lens optics to produce sharper pics, but would it be worth me changing the lens to a Canon EFS 18-200mm IS? (Or possibly a 17-85 IS, but I could do with the extra zoom of the 200mm really) Would that be noticeably sharper the Sigma?
The Canon is right at the top of my budget really, so don't go suggesting £1000+ lenses… 🙂

Sharper? not necessarily,m if anything I'd say the sigma would be noticeably sharper than the canon. The canon has a huge zoom range, to get that range at that price something has to suffer

No.

I don't know the lenses, but like nbt I'd be very surprised if a 18-200mm was sharper than a 17-70mm, even if it is Canon vs Sigma.

Also I would assume that the 18-200mm would be unlikely to be a f2.8 so you'd be losing speed too.

OK, fair enough. So if I wanted the extra zoom, I might as well get another Sigma, rather than spending more on a Canon then?

The 18-200 is a pretty compromised lens.

Sharp 'cheaper' lenses ar considered to be the 18-55IS, the 70-200 F4, the 50mm F1.8 that it sounds like you have.

Unfortunately sharp lenses aren't cheap.

Also I would assume that the 18-200mm would be unlikely to be a f2.8 so you'd be losing speed too.

No, it's not. That's one reason I bought the Sigma in the first place: It's faster then the equivilent Canon.

Sharp 'cheaper' lenses ar considered to be the 18-55IS, the 70-200 F4,

Yeah, I'd considered a 70-200 as well, but that menas carting round another lens on rides, and swapping it over, which isn't ideal from a cleanliness point of view.

As tlr says, I'd have thought and 18-200 lens would be way too much of a compromise, it's bound to be soft at one or both ends?

But I have also found Sigma lenses produce quite unpleasnaltly soft images on my 20D unless they're middle-of-length – I have an 18-50 sigma and its shockingly bad, it has nearly an inch front focus at 1m and if its near either of its extremes it looks like you took the shot at 1/20 handheld.

Keep the 50mm prime its quality lens.

How much could you pick up a Sigma or Canon 70-200mm F2.8 or equivalent?

The canon EF70-200 f2.8 used to be a cracking lens.

Used to sell bucket loads of them when I was in the trade, but that was a few years back now 😉

The 70-200 f2.8 is expensive and heavy for biking.

I carry a 40d with a 24-105 on for biking, with a 10-20 in my bag. Not sure that you'd really need up to 200mm for biking shots on a crop sensor.

Might be better to have a shorter, sharper lens and crop the image as required. Probably produce better results than a cheap, soft 200mm lens.

Took me so long to cpmplete this what I was going to say has been covered – one thing to consider – have a look at the second hand market – for example Ffordes have a good reputation….

Might be better to have a shorter, sharper lens and crop the image as required. Probably produce better results than a cheap, soft 200mm lens.

That's a good point, not something I'd thought of! 🙂

Worth trying the 18-55IS then because they are dirt cheap and you said they are pretty sharp?

I've got a 17-85 IS Canon lens and that's decent enough. There's occasions when I'd like up to about a 105 but not that often. Bonus is that the lens is small enough to fit comfortably in a CamelBak and not that heavy.

SFB uses an 18-200mm VR Nikon lens http://www.bogtrotters.org for all his pics…

you're going to struggle to get a sharp zoom lens without spending serious money. Not sure what you're shooting , but I'd seriously consider additional light, off camera flash etc… so that you can shoot within the aperture range most effective for your lens. Invest in a good tripod and cable release, use mirror lock up when shooting if the subject will allow. Prime lenses with continuos aperture are always better than cheap zooms. Any lens with a higher aperture F1.2 etc… will give you what you're looking for, always go for aperture over image stabilisation – which effectively reduces your chances for getting pin sharp shots.

also, you can hire lenses from places like the flash centre and jacobs are now offering a similar service – try before you buy, just like getting a new bike really.

you're going to struggle to get a sharp zoom lens without spending serious money. Not sure what you're shooting , but I'd seriously consider additional light, off camera flash etc… so that you can shoot within the aperture range most effective for your lens. Invest in a good tripod and cable release,

Mainly I use the camera out on rides, so tripods and the like are never gonna happen!

So, possibly a 18-55 lens, possibly keep the one I have as it's faster (f2.8 vs f3.5) and get a remote flash for when there's less light….

Any other views on that?

the 70-200f4l is pin sharp, it's 1/3rd the weight of the f2.8, it's widely considered to be the best value for money lens you can buy. I love the pictures I've taken with mine, but personally I find I prefer wider angles than longer.

Do you generally use the Sigma wide open at 2.8? Most lenses are sharpest between f8 – f11, which kinda defeats the point of having a fast lens.

But it you are taking photos when you have plenty of light, stick it in aperture priority, stop it down to f8 or so & see if that's any better.

You could always hire the 18-200 lens from here:

http://www.lensesforhire.co.uk/canon-ef-s-18-200mm-f35-56-is-144-p.asp

and see how you get on with it/take some test shots etc.

Do you generally use the Sigma wide open at 2.8? Most lenses are sharpest between f8 – f11, which kinda defeats the point of having a fast lens.

Yeah, is definately sharper when I stop it down. Which makes sense I suppose. More light = Better pics…..

Looking like I should get a flash then…..

Stopped down means less light, not more, so 2.8 is open f16 is stopped down.

For a budget biking lens the 17-85 would be worth a look, when I'm taking biking pictures I generally wish for wider than my 24-105, not longer.

Or the 18-55IS as I suggested, but it must be the IS version, the original non IS are very cheap (£50) and can be a bit soft.

Which makes sense I suppose. More light = Better pics…..

stopping down = narrower aperture = bigger number as it's a reciprocal = less light = subtending a narrower cone at the sensor = sharper (down to about f/11 for DX sensors at which point diffraction kicks in)

Apologies, but having re-read your original post, I don't think that the 17-85 will be any better than your 17-70, and of course its not 2.8.

My final suggestion would be to save your money, buy a few books (eg. Understanding Exposure by Bryan Peterson) and learn some more. I think that you are only likely to get noticeably sharper images by spending a fair bit of money on lenses, and you'd prabably see more of an improvement by learning a few basic rules and tips.

Yeah….what tlr said….

2.8 is wide open, whereas f8 is a smaller aperture (the aperture number is actually a fraction so the bigger the number the smaller the aperture).
I think the increase in sharpness has more to do with diffraction of light around the aperture or something like that. It's not to do with the quantity of light giving you better pics.

I use the Nikon 18-135 lens when mountain biking – it's the kit lens that came with my camera, but I rarely use it above about 50mm. I'd be looking probably for a smaller zoom range, that starts wider – the 17-85 sounds like a good idea.

Given that my camera often gets vert dirty and/or wet there's no way I want to change lenses in (literally) the field, as it's difficult to stop some of it getting on the sensor and hard to subsequently remove it, so I'm willing to accept any marginal loss of sharpness due to lens construction – particularly as it's often limited more by lack of light, movement of subject and hands, and other circumstances

I read that the 18-200mm VR Nikkor is nearly as sharp as primes at the same aperture, and distortion/vignetting isn't an issue as I use DXO Pro to remove it (at a slight loss of field of view)

Stopped down means less light, not more, so 2.8 is open f16 is stopped down.

Sorry, my bad phrasing. What I meant was that to use a higher apeture, you'd NEED more light available, if you see what I mean. 🙂

I think the increase in sharpness has more to do with diffraction of light around the aperture

the aperture is the hole in the iris at the centre of the lens. If you imagine the cone of light from the aperture focussing in on a single pixel of the image, as you open the aperture, the hole gets bigger, making the cone wider, so that a smaller front/back movement at the subject causes a bigger defocussing of the image. Also at the outer part of the cone the light is travelling though parts of the glass where aberrations are less well corrected. Diffraction starts to reduce sharpness when the aperture becomes too small

Most lenses are sharpest between f8 – f11, which kinda defeats the point of having a fast lens.

I believe*, most modern lenses only stop down at the moment of exposure.

So with a faster lens you get a brighter viewfinder image and better AF ability in low light, even if the lens is stopped down for the actual image.

 

* I could be talking bollocks

have a look at the tokina lenses, they do a a full range from 11-135mm at f2.8

i have the 11-16 but am considering getting the 16-55 and the 55-135 as well eventually

the 11-16 is lovely and i think they are available in Canon fit as well as the nikon that i have

I'm a Nikon man myself but had a beautiful 80 -200 F2.8 (all the way) ED lens. Its photographs had such a wonderful quality about them and it oooozed quality. BUT, it weighed a ton and I needed a monopod to use it.
I sold it and bought the Nikon 18-200 VR lens. Whilst its not near as good as the 80-200 was, at least I don't have to swap lenses all the time (letting dust into my camera) and the photos are more than acceptable.

its a trade off convinience over quality.

BTW I do semi pro wedding photography with my 18-200 lens stuck onto a D300. Nobody ever complained about the sharpness or clarity. 🙂

I do miss throwing the background out of focus though. 😕

<slight hijak>
So if I was looking for a general walking round/day to day lens for my 400d to get rid of the crappy kit lens, would the Sigma 17-70 be a good bet? Bearing in mind I already have the 50mm f1.8 prime and Sigma 10-22.

Sorry Pete
</slight hijack>

Toby, looking at the replies here, I reckon you'd be better getting a 18-55IS to replace it. You can get them for about £65-£85 and unless you need the extra 15mm zoom, people seem to think it's a sharpre lens. I had the same lens as you (18-55 non-IS) and TBH the Sigma is not really any better.

I have the Canon 17-85 on a 450D and is a great walkabout lens, but does not have the f2.8 of your Sigma. I picked mine up cheap and would recommend that highly.

After reading all replies above I am not sure you will want it, but I have a 18-55IS lens, hood and polarising filter I could do a deal on?
Apologies for the hijack but mail me if interested.

The canon kit lens is a damn sight better than the sigma of similar range. Never tried an IS one though.

So if I was looking for a general walking round/day to day lens for my 400d to get rid of the crappy kit lens, would the Sigma 17-70 be a good bet? Bearing in mind I already have the 50mm f1.8 prime and Sigma 10-22.

Not sure that the 17-70 is a big step up from the kit lens. I was looking for a good but not ball-breakingly expensive "walking around" lens for a Nikon F100, and chose the Sigma 24-70. So far I've been really happy with it. I don't think you'll see much difference from a Canon or Nikon "pro level" lens.

Second the Sigma 24-70 (iv'e got the non HSM model) as ever does depend on whether or not its a good example

Fortunately mine is and very pleased with it indeed, big old lump though and if you like filters the 82mm is rather pricy I believe

Tamron 17-50 f2.8 always gets good reviews and they have just released an image stabilised version, might tickle my fancy I reckon

I had the sigma 24-70 non HSM and thought it was a good sharp lens. You couldn't expect great results at f2.8 of course, but very good from F4 on. Then I bought a Nikon 24-70 f2.8 and wide open it is as good as the Sigma at f5.6. It is too heavy and too expensive to accompany me on the bike though…

IS or VR works well when your subject is still but you cant beat a large aperture for low light work. Your 50mm prime may not be wide enough for use in forests as you need to be pretty close or trees become an issue (try a 35mm maybe).

The nikon 18-200 was a great one lens does it all solution, and gives good images, only letting it down by being a little slow in low light for moving subjects. good mtb lens if you are outdoors, not great in trees.

One last thing, I dropped my sigma 24-70 f2.8 and it came back a much better lens from Sigma's service and repair centre. Maybe send your 17-70 for some TLC?

Just to say I have the 18-55IS lens and the 17-85IS. I have also had the 18-55 non IS lens as well. Far and away my favourite is the 18-55IS on my 500D. Really nice crisp images and it is very light (about half the weight of the 17-85) which is great for walking and biking. Highly recommended.

HA! Looks like I'm gonna downgade my lens and buy a flash then. Thanks for saving me a heap of cash chaps!
😀

Anybody want a Sigma 17-70? Seriously.

I only carry an EFS 10-22 when I ride. Not found much use for big zooms but then I prefer to get right in there. Shooting at 10mm does mean you've got to let the rider come within about 30cm of you to get a good shot, so you need to trust your subjects! lol

anotherdeadhero did actually almost ride into me at the bike fest in this shot.