17-40L @40mm + 160@f8 - the difference twixt TopRHS and BottomLHS

[I Simonius]

Yup that's the difference (see attached) - COMMENTS PLEASE! :cry:

Seems fine at 17mm but at 40mm, on a tripod, at f8, 160 sec, with spirit level, with mirror lock up+ self timer (yes the 20D has that _ I didn't realise before!)

These shots are 100% crops from top right hand side of pic and bottom left hand side,
that is the SHARP pic is RHS, the BLURRED pic is LHS - the other rhs corner is fine, the other lhs corner os not as bad but not good. The camera was as near as Ican tell on a level plane, as was the subject, and surely at f8, any small tilting of camera would be compensated for, - what could cause this, is it operator error? (i.e. something I've done?)

I also took soem shots close up of Lily stamen, which seemed to me not to have focussed where I put the centre AF point (which I set) but different stamen were perfectly in focus, so is this a focussing issue ALONE or more than that?

[ed2day]

How far were you from the target? Judging from the size of the print you were quite close. May be getting into minimum focus distance issues. At 40mm you should probably be about 7 ft. back. Make that 2 m. for you, sorry. Hey didn't we get our measuring system from you guys anyway?

That looks pretty bad, let's hope it's not the lens. The printing looks distorted too like the page wasn't flat. Is that distortion induced by the lens too?

edit: I assume that's 1/60 sec?

[I Simonius]

How far were you from the target? Judging from the size of the print you were quite close. May be getting into minimum focus distance issues. At 40mm you should probably be about 7 ft. back. Make that 2 m. for you, sorry. Hey didn't we get our measuring system from you guys anyway?

That looks pretty bad, let's hope it's not the lens. The printing looks distorted too like the page wasn't flat. Is that distortion induced by the lens too?

edit: I assume that's 1/60 sec?

about 2 feet from target - no not minimum focussing issues :rolleyes:
I don't know about the rest of the world but I still work in feet and inches :D
I'm sure it's the lens :evil:
Nope that IS 160th of a second :cool:

[ed2day]

I wouldn't give up that easy. If it's that bad at f/8 you should see it pretty easily shooting normal pics. What do you see? Try some brick walls. I would really try moving back a bit. The DOF for really good sharpness at your conditions is about +/- one inch. The margins for error are small. Make darn sure you are really focusing in the center, I'd use manual mode to get the smallest focus area. Try focusing manually. Try tilting the camera slightly to see if you can get the entire scene sharp. The focal plane may be slightly tilted or curved--not desirable, but not nearly as bad as corners that soft. Usually you can kind of eyeball it through the viewfinder--with the aperture wide open (as it is before you shoot) DOF distortions are more visible. Sorry if I'm telling you what you already know, but that's about all I got. I'd want corroboration from another test though. To be that fuzzy at f/8 the lens has some serious problems.

[I Simonius]

I wouldn't give up that easy. If it's that bad at f/8 you should see it pretty easily shooting normal pics. What do you see? Try some brick walls. I would really try moving back a bit. The DOF for really good sharpness at your conditions is about +/- one inch. The margins for error are small. Make darn sure you are really focusing in the center, I'd use manual mode to get the smallest focus area. Try focusing manually. Try tilting the camera slightly to see if you can get the entire scene sharp. The focal plane may be slightly tilted or curved--not desirable, but not nearly as bad as corners that soft. Usually you can kind of eyeball it through the viewfinder--with the aperture wide open (as it is before you shoot) DOF distortions are more visible. Sorry if I'm telling you what you already know, but that's about all I got. I'd want corroboration from another test though. To be that fuzzy at f/8 the lens has some serious problems.

Thanks but Iv'e thought about it and thought about all the lenses Ive had and used in the past...- judging from the perspective of that collective experience - this ain't right at all, by any means - it's going back :evil:

[RichardtheSane]

At a distance of 2 feet and 40mm your DOF will be 1 1/5 of an inch either side of the focus point.

How flat was your subject? On the crop it looks like it wasn't flat but I can'e see very well.

Certainly looks OOF though! It the distance was definitly within that scale send it back. Might be worth doing a proper sharpness test...

[I Simonius]

At a distance of 2 feet and 40mm your DOF will be 1 1/5 of an inch either side of the focus point.

How flat was your subject? On the crop it looks like it wasn't flat but I can'e see very well.

Certainly looks OOF though! It the distance was definitly within that scale send it back. Might be worth doing a proper sharpness test...

Never mind all that malarkey - that was too OOF and odd to be within the normal operating parameters.
Gota replacement - here's a pic from the corner 100% crop, it's the same at all corners :D
THAT's more like it!
ps this is taken even CLOSER than the previous shots, so DOF will be LESS :cool:
scuse the tripod leg :rolleyes:

[Tom W]

I was all set to reccommend that you double-check that the newspaper was perpendicular to the lens axis (parallel to the sensor), but it appears that you already had that issue sorted out. The replacement looks like a winner, and is more like the results I had gotten with my copy.

I had a Sigma 20mm that resembled your first copy, though it was a left-right rather than top-bottom issue. Probably one lens element mis-aligned in there somewhere.

Did you explain to the store what the problem was?

[I Simonius]

snip
Did you explain to the store what the problem was?

Only to the extent that it was to do with OOF on one side at 40mm
No quibble at all, changed instantly :D
That's why I buy my stuff from a shop and not online - humans!

[Tom W]

Only to the extent that it was to do with OOF on one side at 40mm
No quibble at all, changed instantly :D
That's why I buy my stuff from a shop and not online - humans!

It's nice to have a shop within 100 miles that sells decent stuff - no such thing here.

Glad that they were easy to deal with - that's good to see. :)

Reason I mentioned it is that if the store doesn't really have a good reason for exchange, some will just put the stuff back on the shelf. On the one hand, many returned items are not really defective, though on the other hand, some stores will re-shelf products regardless of whether they are defective or not as long as the defect doesn't show. In this case, it's obviously better that the lens go back to Canon for adjustment or rebuild or something.

[ed2day]

How many open-box/refurb sales have you seen on lenses? Of course they go right back on the shelf.

Simon--glad you got it sorted out. It's a great lens.

[Tom W]

How many open-box/refurb sales have you seen on lenses? Of course they go right back on the shelf.


Some do, some don't. Depends on what's wrong with them - if anything. And it depends on the dealer. And it depends on how well the unsatisfied customer explains the problem. Just saying "it doesn't work right" doesn't give a dealer much incentive to believe that the customer isn't just having second thoughts about their purchase. However, if they explain what was wrong and it's a reasonably scrupulous dealer, it will go back to the manufacturer.

I wonder what the price of lenses would do if they sent every returned lens back to the manufacturer for rebuilding.