What do you get with a lens that costs 10x its cheaper alternative?
 

Hi,
To be more specific with my question...

What makes the Canon 17-40 f4L worth approximately 10x the price of the kit lens? or 1.5x the price of a Tamron 17-50mm f2.8?

Would you agree that, in the hands of a skilled photographer it would be hard to see the difference, if no, what would be the defining factor?

For a bit of grounding, I am a 400D user with a lens kit made up mostly of manual focus lenses + the 18-55mm kit lens. I am looking for a new lens and am considering both 17-50mm Tamron and the 17-40mm canon L.

I look forward to your replies with interest.


Hardy

Build quality, AF speed and sharpness. Makes no difference whether you're a pro or not, there are differences that can clearly be seen. Whether that matters to you is dependant upon just what you do with your images.

I started out with kit lenses (the Nikon 18-55mm and 55-200mm - IMHO the worst lenses I've ever held) and while I got some good images, it was the images I missed that made me upgrade. Now if my images are not sharp or soft in places, I have only myself to blame.

That doesn't mean that all 'cheaper' lenses are crap though, as there are some real gems out there. The Nikon 18-70mm is a great little lens and the Sigma 10-20mm is the dogs gonads.

Edit. I will also add, one of my sharpest lenses is also my cheapest. Get yourself a 50mm prime for as little as £50 - money very well spent.

With lenses you really do get what you pay for....

Although some of what you pay for may be the brand name or a white finish. I use mainly sigma EX lenses, which are substantially cheaper than the canon L equivalents, and where I have done head-to-head comparisons, there has been very little if any difference in image quality. (This was between the 70-200 f2.8 models in the two ranges)
I actually prefer my sigma 28-70 over my canon 24-105L when used over the 28-70 range.

I agree with the above - you gets what you pays for - but even some of the top manufacturers can turn out a dummy - quality control needs to be born in mind. Use a dealer where you can try out the lens on your camera - take a couple of test shots and see its results for yourself. Also remember that some second hand lenses - of discontinued models were the best people could turn out for a decade or more and are still well worth using - eg: Nikon 80-200 f2.8 AF-S replaced by 70-200 F2.8 AF-S VR. If you can find a good one and don't need VR it is still probably one of the best Nikon ever made.

Kit lenses can produce very good results if you stop them down to smaller apertures and avoid using them at the extremes of their zoom ranges. The more you pay for a lens, the less critical this becomes. Kit lens wide open at max zoom (for example) will produce softer, less defined results than a premium lens under the same conditions.

Don't know about the Tammy 17-50 but I have the 17-40 and it is a superb lens IMO.

I used to think that the Sigma EX lenses were right up there with the Canon L's, I owned a 500 f4.5, a 100-300 f4 and a 70-200 f2.8. I got the chance to upgrade my 500 to the Canon (as you know). Initially I didn't think there was much in it, but once I got to grips with the Canon I started to see why it costs so much more. The IQ is noticebly better and it performs better in really testing conditions, in good light there's not much between them.

I then tested my 70-200 f2.8 against the Canon 70-200 f4 and far prefered the Canon - images are that bit sharper and the colours are richer. After that I realised that while cheaper lenses can do the job there really is an advantage to top end glass.

As for the 18-55 kit lens vs the 17-40 f4, there is a world of difference between them - sure both can take got photos, but the 17-40 will do so more consistently, especially when conditions are less than ideal.

Having seen your images with the canon 500 f4 I'm sure you're right about it. (And I expect that applies to other extreme lenses too). I would also agree that 'kit' lenses are a step down from the 'good glass' of top ranges of all brands, both in image quality and build quality.
My experience with the mainstream focal lengths across different brands of 'good glass' suggests the differences are subjective - as you say, colour rendition and contrast for example. One reason I dont like the 24-105 much is that I find it harder to use hyperfocal focussing with it compared to my sigma lenses, so there are familiarity and ease of use issues as well.

Slightly off topic but I was with a guy only last week who was shooting birds with a Sigma 135-400 f5.6 lens and I was using a Canon 400mm f5.6 L. My lens was focusing in a fraction of a second every time but the sigma was forever hunting for focus and sometimes it could not obtain AF at all - this was shooting exactly the same bird at the same time in the same light at the same focal length.