Lens Copies - is there such a thing as a "good" or "bad" copy of a lens?

I am currently researching my next lens purchase and have come across quite a bit of discussion on the same type lens having much different image quality. It just depends on if you happened to purchase a good "copy". Some guy on another site was selling a
70-200 f2.8L and said this "particular copy was by far sharper than his previous four copies". Can this be legit? Do the same lens's vary that much in quality? That's kind of scary in my opinion.:eek:

What say you?

Others may disagree with me (in fact I'd almost guarantee it), but in my opinion - unless the lens has been "physically stressed" in some way, I just don't buy into this "good copy / bad copy" thing.

As I see it, they're all made the same way - all tested after manufacture - the camera AF works on a closed-loop system - and I've never had anything approaching a dud.

Just my 10c worth!

I would have to agree with Colin. The people claiming lenses are better depending on which "copy" you get are probably the same who believe the moon landing to be a fraud. :o

Thanks guys, I just couldn't see a reputable lens makers putting out a product that was so hit and miss. Especially at the cost of the darn things.:eek:

Colin

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Originally Posted by Colin O'Regan

Thanks guys, I just couldn't see a reputable lens makers putting out a product that was so hit and miss. Especially at the cost of the darn things.:eek:

Colin

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Call me "simple", but I suspect that the quality control on the manufacturing side is probably a lot tighter and repeatable than the quality control in the 'global end-user casual evaluation' program!

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Originally Posted by Colin O'Regan

It just depends on if you happened to purchase a good "copy". Some guy on another site was selling a 70-200 f2.8L and said this "particular copy was by far sharper than his previous four copies". Can this be legit? Do the same lens's vary that much in quality? That's kind of scary in my opinion. :eek: What say you?

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Yeah, I bet all these “comments” are the World Wide Web . . .

Lenses are made to fit with tolerances. Cameras are made to fit within tolerances. Get a lens which is scapes into tolerance at the [+ LIMIT], and match it with a camera which scapes in at the [– LIMIT] and then you will have the worst case scenario (barring a faulty item slipping though the net).

I think that extreme mismatch might happen on odd occasions and sometimes it will be noticed by an experienced Photographer, with a keen eye, using a lens often and in a variety of circumstances.

Also, I think the latitudes of performance limits are different between Companies and Manufactures. Also within one Manufacturer there could be “A” Grade and “B” Grade Items

But we are talking about a Professional Quality Lens which is pretty standard fare for most Professional Sports and News Photographers – these guys who are at the top of their game, are a very noisy bunch if disgruntled.

I got a 70 to 200F/2.8L. I got several mates with 70 to 200F/2.8L. I am reasonably careful with my gear. Some of my mates don’t use lens caps – neither end – nor filters, and some use a duffle bag for the lenses and the lenses share space with the empty coke cans and sometimes the odd banana peel.

I have never had a problem with Image Quality using my Mate’s L lenses on my DSLR's – and they have never complained about mine. I have never had a dud 70 to 200 from a News Pool Kit – and some have been pretty worn and battered.

My mates and I (generally) live in the real world (though sometimes escaping via a nice Red) and we generally don’t look at the corners of images at 3000% magnification . . .

I think the internet is great vehicle to share information.

I think it is also the internet offers the opportunity for misinformation and anonymity.

Sometimes the temptation to supply misinformation within the cloak of anonymity is enough just make some people feel important.

WW


PS: All the 70 to 200F/2.8L I have used have done their job well.


http://backup.cambridgeincolour.com/...9193571-md.jpg


And, in an emergency, even with a x2.0MkII on board:


http://backup.cambridgeincolour.com/...9193632-md.jpg

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Originally Posted by Colin Southern

Others may disagree with me (in fact I'd almost guarantee it), but in my opinion - unless the lens has been "physically stressed" in some way, I just don't buy into this "good copy / bad copy" thing.

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Colin, I really, Really, REALLY, tried hard to disagree with you, even in the smallest tiniest detail . . . but I couldn't find anything to argue about.

The topic of "my good copy" vs. "your bad copy" gets up my snooter too.

WW

Out of interest Bill, ...

... someone posted a question some time back that I never really did find a good answer for.

If we have a lens that squeaks in at the PLUS limit, and it's mated to a camera that squeaks in at the MINUS limit, why would focus accuracy be affected when focusing is a closed-loop affair?

Something I've been meaning to dig into a little deeper.

PS: Your swimming shots reminded be of one I saw yesterday of swimming champ Michael Phelps - that guy has some upper-body physique! (looks almost more like a machine than a human!),

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Originally Posted by Colin Southern

Out of interest Bill, ...

... someone posted a question some time back that I never really did find a good answer for.

If we have a lens that squeaks in at the PLUS limit, and it's mated to a camera that squeaks in at the MINUS limit, why would focus accuracy be affected when focusing is a closed-loop affair?

Something I've been meaning to dig into a little deeper.

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Hi Colin,

That may have been me! (although I wasn't the first)

I think focusing isn't (can't be) a closed loop when not done using the main sensor, as most DSLR cameras don't of course, except in Live View (but not with the Sony A300/A350).

My (new) Sigma 18-250mm DC OS lens, on my D5000 had, and still has, definite AF errors. :(

The original problem was that at all focus distances, it took shots focused some 5% behind where the AF sensor thought it was right. This was most noticeable at the 250mm end, as you'd expect.

Sigma have had the lens (alone) back once and managed to get it right at 250mm for distances over say, 2m, but closer than that (it focuses down to 0.45m), it is still wrong. e.g. focus on a butterfly's head and get its rear end sharp!

It also still, or now, seems to have the original problem at intermediate focal lengths, say in the 40-150mm range. I've lost a few holiday shots due to that :mad:

Sigma now want both the camera and the lens to "do the job properly", so I'll 'be without' for a while :(:(

So now I have to package both up, send them off, wait for about a week to get them back (hopefully in one piece).

Not a good experience

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Originally Posted by Dave Humphries

I think focusing isn't (can't be) a closed loop when not done using the main sensor, as most DSLR cameras don't of course, except in Live View (but not with the Sony A300/A350).

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Hi Dave,

It's definately not a "closed loop" as far as involving the sensor goes, but I would assume that the AF module would be aligned with the sensor to some VERY tight tolerences.

Actually - the penny just dropped a bit - theres one sort of "max limit / minus limit" tolerance that Bill referred to right there!

If I find the time, I'll drop Chuck Westfall an eMail to ask - he's a walking / talking encyclopaedia of Canon technical knowledge, and is usually able to get back to me within a day (great chap - wonderful assett to Canon).

To stir the pot a little (!) is it not interesting that the Canon 5DMkII actually includes a "micro adjust" feature, to allow you to make (and I quote from the manual) "fine adjustments for the AF point of focus"?

I recently acquired an old, but immaculate, 70-200 F4L (non-IS) which seems to be slightly back-focusing. I am not normally a pixel-peeper but the test shots I took with it just happened to make me question the accuracy of the focus. I've never had any reason to question focus accuracy on any other lens I've ever owned.

I'm intending to carry out some tests this weekend and maybe have a play with the microadjust feature - will report back!

Excellent! Thanks for the response. It most certainly has to be the exception and not the rule. However, when you start looking for the horror stories on the (net) then that's all one will find.
I've yet to find one scarier than William W. though.....

"I got a 70 to 200F/2.8L. I got several mates with 70 to 200F/2.8L. I am reasonably careful with my gear. Some of my mates don�t use lens caps � neither end � nor filters, and some use a duffle bag for the lenses and the lenses share space with the empty coke cans and sometimes the odd banana peel.":eek:
Sheesh, you guys must have great sponsors.;).
Great shots by the way William.

At any rate, I feel much better about not buying a "dud".

Thanks, Colin

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Originally Posted by GillR

To stir the pot a little (!) is it not interesting that the Canon 5DMkII actually includes a "micro adjust" feature, to allow you to make (and I quote from the manual) "fine adjustments for the AF point of focus"?

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Since it's the AF module that ultimately controls the focus - and I'm guessing that the AF module would have to be aligned fairly precisely with the sensor (in terms of distance etc) (even though there's probably a calibration factor stored and applied by the firmware) - the micro adjustment gives you the ability to over-ride this.

I had a play with it a while back, and came to 2 conclusions ...

1. That although it has (off memory now) 20 possible adjustments in either direction, I coudn't tell the difference with anything smaller than a 5 step change.

2. Overall, I couldn't get it any better than the camera already was. Best I could do was to get - arguably - a tiny improvement in one position (with a zoom lens), only to have it a tiny bit worse at another focal length.

One thing I did notice and that's that correct capture sharpening had a far far far far greater effect on sharpness when viewed at 100% (capture sharpening STILL seems to be something that most don't apply).

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Originally Posted by Colin Southern

One thing I did notice and that's that correct capture sharpening had a far far far far greater effect on sharpness when viewed at 100% (capture sharpening STILL seems to be something that most don't apply).

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Trust me, in my case, this is beyond sharpening;

These are screen clips from Nikon View NX, which show the focus point used and where it was targeted, now compare the areas of sharpness.
http://backup.cambridgeincolour.com/...2/original.jpg http://backup.cambridgeincolour.com/...3/original.jpg

Focus on branches = reeds behind in focus
Focus on water several feet in front of branches and 'hey presto'; the branches are now sharp
These are crops at 100%.

At the focal length and distance shown above, this has now been resolved (I believe), but at other focal lengths (< 80mm) and distances (< 2m), it still exists. :(

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Originally Posted by Dave Humphries

At the focal length and distance shown above, this has now been resolved, but at other focal lengths (< 80mm) and distances (< 2m), it still exists. :(

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*** Cough *** Haven't had any issues with my (Canon) camera and (Canon) lenses *** cough *** :D

(Sorry, couldn't resist!) (I blame the lateness of the evening!)

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Originally Posted by GillR

To stir the pot a little (!) is it not interesting that the Canon 5DMkII actually includes a "micro adjust" feature, to allow you to make (and I quote from the manual) "fine adjustments for the AF point of focus"?

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Hi Gill,

Yes, originally I thought the Nikon D90 had this too, but apparently not.

My original query thread;
https://www.cambridgeincolour.com/forums/thread1885.htm

That's why I initially wondered whether I was being unreasonable, but I think the magnitude of the error makes this an "unfit for purpose" trading standards issue, not that I intend to go that route unless I have to.

Regards,

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Originally Posted by Colin Southern

*** Cough *** Haven't had any issues with my (Canon) camera and (Canon) lenses *** cough *** :D

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Indeed, Colin :o

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At the focal length and distance shown above, this has now been resolved (I believe), but at other focal lengths (< 80mm) and distances (< 2m), it still exists. :(

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Hi,
I am a newbie in researching and purchasing a digital SLR with a bias towards Pentax but I am worried by the 'apparent' quality control complained about on Pentax forums with photos showing similar problems. In one extreme case a graduated chart , tilted horizontally away from the lens showed a distinct difference, in focus , between left and right side of the lens. On this website there were many complaints where lenses had to be returned.
I am thinking of purchasing the Pentax K-x as an entry level m/c but am worried about the lenses.
Any suggestions?

Good copy , Bad Copy.... I stay with the original and I have never a problem, The reason, I do not want to take a chance on a valuable one time chance photo. Although, I am not a gambler.

Many people learning about photography gets confused about how to "check for lens sharpness" (aka "do I have a good copy"). I asked a friend of mine to create this tutorial on how to test your lenses for sharpness since I am clueless on video production. He was more than gracious enough to do this:) for me.

This tutorial applies to commercial and consumer grade lenses.

http://www.youtube.com/watch?v=HS0hlQ9lSps