L lens purely for aps sensors

[flake]

Well here are the crops at f/4 100%




Yes the corner one is a lot bigger, but it does go to show that the centre is just what you'd expect from a L lens and the corner isn't! Yes I know it's at f/4 but the resolution should be better than this!

[donoreo]

Guess I did miss your point I really thought it was a complaint about the crop

[anglefire]

Looks mostly out of focus to me. With some CA on the branches. Nothing worse than expected - and at the risk of repeating myself, at real world levels and not 100% crops, the lens is just fine.

And yes, Donoreo, the OP was about the lack of crop "L"'s, but that was explained several posts ago.

[flake]

It might look out of focus, but it isn't. The centre of the frame is in sharp focus and as the shot was taken parallel to the building it should also be in focus, I know that it is because I have the whole image to look at. What this is showing is the loss of resolution at the extreme edges of the frame, albeit in a rather false situation, where the aperture is wide open. If you compare the performance of this lens on a crop frame camera it is very much better than on a full frame one which is why the OP believes the L lenses out perform the APS-C ones.

It should be bourn in mind though that this lens being one of Canons top flight L series should perform better than this, you may not be too bothered about 100% crops, but there are others who are, and it's important for me to know what parts of a lens are not really useable. What this goes to show is that in the real world the findings of Photozone are in fact correct.

"The problem is, again, the 17mm setting. The center and even the border performance is very high here but there isn't really anything left deserving the word "resolution" in the extreme corners at f/4 and f/5.6. If you require at least a decent corner resolution you should stick to f/11 at this focal length. "

"it seems as if Canon has overstretched things a little with respect to the 17mm setting. The lens is able to deliver a very high resolution for most of the image field but the corner performance is poor thus spoiling the game here - this is like cappuccino without the cream for a ultra-wide lens where corner to corner sharpness is simply more critical than for a tele lens for instance. High vignetting and heavy distortions on top don't make things any better here. "

Please note that all lenses do show a loss in resolving power when used on a full frame camera, and the higher the MP count the more noticeable it becomes. This particular lens is not unique here, but does provide a good example. There is also a test on a crop frame body where it performs very much better, it's worth reading the two to gain an understanding of the fall in performance at the edges when used FF

[Forseti]

Originally Posted by flake

What this is showing is the loss of resolution at the extreme edges of the frame, albeit in a rather false situation, where the aperture is wide open.

This is one argument that I'm definitely not getting involved in LOL but, might I ask what's the point of demonstrating something in, as you say, 'a rather false situation'? Scratching my head I cannot come up with a possible scenario that one would use a wide open aperture at 17mm or am I missing something here?

[Robster]

http://www.warehouseexpress.com/buy-...2403#bvreviews

Have a look at the reviews from customers about the 17-55mm F2.8 a couple have replaced the 17-40mm L with it
rather interesting again.
Have I opened a can of worms here?

[flake]

f/4 isn't particularly large as apertures go but imagine a table setting where you want some in focus and the background blurred as an example, How about a stack of shopping trolleys where the logo of the store is in sharp focus and the rest blur nicely away? So long as the scene is relatively distant the depth of field at 17mm f/4 should be sufficient, so you might want to use a wide aperture in low light hand held. I did some architechture recently (with a different lens) that could easily have been done at f/4, I actually did it at about 28mm f/8 and the fall off in resolution towards the borders is still noticeable, though not anythig like as much.

At f/4 it's the worst point of the lens, but it doesn't really become useable until f/11 which is quite a small aperture.

The newer high pixel count FF cameras really show this effect, and if Canon release the 1Ds MkIV with a 39MP sensor it'll be even worse as the centre of the image will be high res and the borders won't! If you imagine a camera like the 5D with 12.8 MP the resolviing power across the image is more or less the same so it's not as noticeable, however the MkII with almost double the pixel count is out resolving the lens at the borders noticeable in the image.

Wide angle lenses probably show this problem more than any other, the 70 - 200mm f/4 is apparantly much better, but as Photozone say it's much less important in a telephoto lens than in a wide angle.

Canon appear to have found it difficult to design a lens to compete with Nikons 14 - 24mm however they have recently applied for a patent on a new wide angle design which appears from the drawings to resemble the Nikon in having a bulbous front element, I'm sure that this will perform better than the current model.

[anglefire]

If its that much of an issue Flake, then get decent primes. Or sell up and go Nikon.

Zooms will always be a compromise, some more than others. The 17-40mm design is at least 5 or 6 years old, so technology has moved on.

Anyway, this is now way off topic so I'm out of here!

[duncan22]

Not sure how accurate this is but a number of sites reviewing L lenses against ef-s lenses make the point that L lenses are better built and are sealed better against dust.
Some users say that the 17-55mm IS USM 2.8 takes as good if not better pictures than some L lenses others disagree.
I'm sure in many cases it comes down to personal opinion otherwise the issue would be clearly settled !

[Forseti]

Originally Posted by duncan22

Some users say that the 17-55mm IS USM 2.8 takes as good if not better pictures than some L lenses others disagree.

It may well do but as I've personally never had one to compare I couldn't say. Remember though this is an EF-S lens which isn't suited for full frame cameras which is fine if one is absolutely sure that the route to ownership of a full frame camera isn't for them. Whilst of course the option of buying and selling is always open later on I think it's important to note and take into consideration this fact before purchasing any EF-S lens.