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Author Topic: Canon L lenses and quality control  (Read 20573 times)
Giedo
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« Reply #20 on: April 21, 2006, 08:13:04 AM »
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If I were a camera / lens tester, I would get 10 similar lenses at 10 different locations and start testing as to provide some objective facts instead of all this hearsay.

Actually I found a very objective way to get my lens tested. I provided my Tamron Macro lens to Klaus from www.photozone.de. He tests lenses individually that are provided by readers from his website. result: fabulous lens. But I have to say that the quality before and after this test is exactly the same ;-)) So in that sense I agree with Ray.
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Mark D Segal
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« Reply #21 on: April 21, 2006, 08:22:14 AM »
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If I were a camera / lens tester, I would get 10 similar lenses at 10 different locations and start testing as to provide some objective facts instead of all this hearsay.

Actually I found a very objective way to get my lens tested. I provided my Tamron Macro lens to Klaus from www.photozone.de. He tests lenses individually that are provided by readers from his website. result: fabulous lens. But I have to say that the quality before and after this test is exactly the same ;-)) So in that sense I agree with Ray.
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Giedo, don't dismiss the findings of experienced photographers as "hearsay". I've been making photographics for 50 years and I know what I expect from USD 1200 worth of lens. For most people the idea that you could put together a sample of ten copies for comparison testing is totally on another planet. Not even the people who test this equipment on the various websites we usually read do that. A sample of one is not a valid testing procedure - that much I agree with you, but that is a separate issue from the fact that there is enough evidence of a QC problem in Canon's "L" department that they need to look into it. If the best they make is supposed to be the best they make, they should do more to ensure each piece is properly tested to a minimum acceptable standard for "L" before it leaves the factory.
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Mark D Segal (formerly MarkDS)
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jjphoto
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« Reply #22 on: April 21, 2006, 09:16:54 AM »
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I think they should simply set a standard for what "L" means, test each piece before it is intended to go out the door and not ship anything that doesn't meet it.
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"L" only refers to extraordinary component elements or manufacturing techniques (ie. glass such as flourite, UD or aspherical elements).

"L" is NOT an indicator of image quality, only of the effort and cost involved in manufacturing a lens. Some, maybe many, non "L" lenses outperform "L" lenses. I have a 100/2.8 USM (NON "L") which outperforms the other 3 "L" lenses  I have.

JJ
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Mark D Segal
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« Reply #23 on: April 21, 2006, 09:30:21 AM »
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Thanks for clarifying the meaning of "L". That is helpful. Underlying that, one supposes they do these things to achieve a higher quality standard. One should therefore expect that for any Canon lens with the same focal length and f/stop range an "L" version should deliver better image quality than a non-L version. That much said, perhaps they don't make any pair of lenses like this, so one cannot really make an apples-to-apples comparison of the same thing in an "L" versus a "non-L" version! All I know is that if I pay 1200 bucks for an "L" lens, which is supposed to be their best, I don't want to habe to worry about variable sample quality to the extent of noticeable differences from one copy to the next.
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Mark D Segal (formerly MarkDS)
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jjphoto
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« Reply #24 on: April 21, 2006, 05:15:04 PM »
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All I know is that if I pay 1200 bucks for an "L" lens, which is supposed to be their best, I don't want to habe to worry about variable sample quality to the extent of noticeable differences from one copy to the next.
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I hear you girlfriend, but that aint the real world. Personally I would only buy from a reputable dealer who is willing to replace the lens if it doesn't meet your performance standard.

JJ
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Ray
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« Reply #25 on: April 21, 2006, 09:21:26 PM »
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Ray, did you really mean that? I think they should simply set a standard for what "L" means, test each piece before it is intended to go out the door and not ship anything that doesn't meet it.
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Mark,
I really mean it. I hate waste. I understand when Intel produces a processor chip that doesn't meet specification but still works, they label it as a slower processor. They don't necessarily junk it. (At least, that's what I've read, but it could be a myth.)

I suspect it is not practical or economical  to manufacture a complicated item like a lens and ensure that each copy is exactly the same. If it's necessary to test each individual lens to ensure performance consistency, then let some of us poor folks get the rejects at a discount. As long as I'm provided with reliable information regarding the lens' failing (through an MTF chart, for example) I might be able to live with it.
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David Anderson
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« Reply #26 on: April 22, 2006, 01:10:18 AM »
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I borrowed a 24-105 L for a rafting trip from Canon CPS, and was happy with the shots, yes there was some distortion issues, but nothing that the average reader would see.
It's an easy lens to live with if you don't want to change lenses all the time, ot like me you were in a situation that demanded low weight.

A couple lenses I've sent to Canon for calibration have come back with very good results, like my 16-35, now tack sharp at both ends..

One last thing, make sure you check the focus calibration on your camera with other lenses before you blame just the lens, I found one of my markII DS's front focused only enough to be noticed on the fast lenses wide open.
After another trip to Canon it's all better.

David.
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Mark D Segal
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« Reply #27 on: April 22, 2006, 07:04:23 AM »
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I suspect it is not practical or economical  to manufacture a complicated item like a lens and ensure that each copy is exactly the same. If it's necessary to test each individual lens to ensure performance consistency, then let some of us poor folks get the rejects at a discount. As long as I'm provided with reliable information regarding the lens' failing (through an MTF chart, for example) I might be able to live with it.
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Ray, what you are saying makes some sense, but I think it would be an administrative nightmare for the manufacturer and the retailer. It is a pandora's box for endless disputes with customers, while the manufacturer still needs to put the resources into individually reporting on each piece it manufactures. As complex as the manufacturing may be, I believe they are technically savvy enough to set a MINIMUM standard for a particular grade of lens (which would be high for an "L" lens) and meet it every time. If they surpass it from piece to piece, well that's a bonus for the guy or gal who buys it - but not a corporate obligation, while the rest of us know what we buy meets the minimum standards for the price point.
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Mark D Segal (formerly MarkDS)
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Ray
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« Reply #28 on: April 22, 2006, 08:38:49 AM »
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Ray, what you are saying makes some sense, but I think it would be an administrative nightmare for the manufacturer and the retailer. It is a pandora's box for endless disputes with customers, while the manufacturer still needs to put the resources into individually reporting on each piece it manufactures.


Mark,
I honestly can't see why this should be the case. Three different grades of the same model of lens would in practice simply be 3 different models of lenses which happen to all have the same basic characteristics. If a customer decided to upgrade from Grade C to Grade A and discovered that his old Grade C was in fact better than the new Grade A, then one would expect that a refund or replacement would be provided without drama. The only administrative nightmare that might occur would be in the QC and MTF testing department of the manufacturer, and rightly so.

In other words, full testing and grading of each individual lens is the best form of quality control one can have. Mistakes would be made, but over all quality within each grade would be more reliable and consistent. Such a system would also lend itself to better and more informative scrutiny from reviewers who would have a better standard against which to judge a lens, it's own MTF chart and/or a different grade of the same model.

Such a system should also help the manufacturer (or brand owner) with marketing decisions and enable them to better serve the customer. They would get a clearer idea of the demand/quality/price relationship for particular designs and types of lenses. The consumer would also have greater number of choices. Is that a bad thing?  
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Mark D Segal
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« Reply #29 on: April 22, 2006, 10:04:39 AM »
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No, it is not such a bad thing per se, but it just won't happen - no way I can imagine Canon firstly admitting to the who concept, then sitting down to work out these quality grades and conform every lens they manufacture, say within the "L" line to one of those grades.
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Mark D Segal (formerly MarkDS)
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Mark D Segal
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« Reply #30 on: April 22, 2006, 10:11:12 AM »
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I hear you girlfriend, but that aint the real world. Personally I would only buy from a reputable dealer who is willing to replace the lens if it doesn't meet your performance standard.

JJ
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JJ, I see you are new to this Forum. I'm not a girl, not your girlfriend (your real girlfriend - if you have one - should be insulted   ) and we have standards of dialogue here which I would recommend you respect.

Apart from that, I agree with you about having return privileges for such purchases - very important.

Cheers,

Mark
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Mark D Segal (formerly MarkDS)
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Ray
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« Reply #31 on: April 22, 2006, 11:45:16 AM »
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No, it is not such a bad thing per se, but it just won't happen


Mark,
You are probably right. It won't happen, but I still think it's a good idea. The best we can hope for is that QC methods and manufacturing tolerances will improve with advancing technology. In the meantime I'll just have to do my own testing.

I was in Chinatown in Bangkok recently buying a 580EX flash unit. The price was so good I enquired about the Sigma 12-24, which is a lens I want but which has a reputation for quality variability. Because I'd already made a purchase, the store was willing to offer me a special price on the lens; much cheaper than I'd pay in Australia. I was sorely tempted, but didn't have the means with me to test the lens (ie. laptop, my own copy of the Sigma 15-30 with which I'd compare it, etc.). It was the last day before Songkran and the store was closing for the week. I didn't have the opportunity to return. I didn't buy the lens.

On reflection, this is a sad state of affairs when a customer wants a lens but doesn't buy it because he doesn't have time to test it.
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macgyver
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« Reply #32 on: April 22, 2006, 11:55:34 AM »
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JJ, I see you are new to this Forum. I'm not a girl, not your girlfriend (your real girlfriend - if you have one - should be insulted  ) and we have standards of dialogue here which I would recommend you respect.
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Easy now mark, JJ was not calling you a girl.  It's an expression.

Also, how long does it typically take for one of your bodies/lenses to go to and from canon service?  I would love to send one in, but I shoot for a daily and have a hard time finding an opening to do so.
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Mark D Segal
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« Reply #33 on: April 22, 2006, 12:11:51 PM »
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macgyver, OK, I've never been treated to that expression before. Thanks for the heads-up.

Sorry I can't advise about turnaround time at Canon. What country/city are you in? Here in toronto they do have a special service window for members of their accredited Professionals customers, and I believe they provide quite rapid turnaround for those folks - but I suppose it also depends on what you need done.
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Mark D Segal (formerly MarkDS)
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Mark D Segal
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« Reply #34 on: April 22, 2006, 12:16:05 PM »
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I was in Chinatown in Bangkok recently .................... I didn't buy the lens.

On reflection, this is a sad state of affairs when a customer wants a lens but doesn't buy it because he doesn't have time to test it.
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I would have made exactly the same decision under the circumstances.

BTW, did you take any shots in Chinatown at night there? I found it very photogenic.
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Mark D Segal (formerly MarkDS)
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Ray
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« Reply #35 on: April 22, 2006, 08:51:06 PM »
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BTW, did you take any shots in Chinatown at night there? I found it very photogenic.
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Unfortunately not. I was travelling with a female companion and felt somewhat constrained with regard to photographic activities. However, I plan to revisit Angkor Wat in August/September, by myself, and should then have an opportunity to test a few copies of the Sigma 12-24, a lens I'll need for those huge structures in the jungle. I'll check out Chinatown by night also   .
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Anon E. Mouse
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« Reply #36 on: April 23, 2006, 06:15:12 AM »
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Lens manufacturers manufacture their lenses to defined tolerances. They are also under a great deal of preasure to keep prices down - $1,200 is not a lot of money for the technology you are buying. So they are balancing the consumer demand for inexpensive optics with the demand for high-quality optics. And the advances in optical design and manufacturering today are amazing. Try comparing your modern zoom lens with one produced in the 70s.

Has anyone here ever made an MTF curve for a lens? Do you know how long it takes? (Hint: 4 - 5 hours.) Do you know how much those machines cost? Then to place every lens on the machine and generate curves would be such an investment to the manufacturer that the cost of the lenses would shoot up. I seriously doubt anyone would want to pay for it.

Then there is another headache for the manufacturer. Customers comparing their MTF results and demanding their unit match the best sample curve they can find. Not only would this make your lenses even more expensive, but it is also silly as the MTF curve can detect variations that cannot be seen in the image. Amateur MTF "experts" are not worth the manufacturer's time.

The current system is good. If the average quality of manufactured lenses where really as random as this thread suggests, then there would be a lot more complaints than you see here. You have a better chance to get a good lens than you do a bad one.
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Mark D Segal
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« Reply #37 on: April 23, 2006, 06:52:10 AM »
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Anon, thanks. You've spelled out in detail why I think it is impractical to try implementing refined systems for grading the eggs. You speak of "defined tolerances" and I think that is where the issue is. While the real cost has come down and the quality gone up over the years, that is all sunk-cost and sunk-benefit if you will - people evaluate now for now and ask whether my 1200 dollar lens is as sharp and free of distortion as the next guy's or gal's, and if there are visible differences we get uncomfortable. So the issue is to define these tolerances in a way that keeps us happy - especially those buying at the high end, regardless of whether the high end is now lower than it was in 1970.
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Mark D Segal (formerly MarkDS)
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Ray
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« Reply #38 on: April 23, 2006, 08:34:22 AM »
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Anon and Mark,
Thanks for playing the role of Devil's Advocate. A good idea always needs testing   . Let me now dispel some of your negativity (if not completely annihilate it   ).

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Has anyone here ever made an MTF curve for a lens? Do you know how long it takes? (Hint: 4 - 5 hours.) Do you know how much those machines cost? Then to place every lens on the machine and generate curves would be such an investment to the manufacturer that the cost of the lenses would shoot up. I seriously doubt anyone would want to pay for it.


Photodo is the only company I know of that has produced reliable MTF data for a variety of lenses. Their numerical rating for each lens may be a bit suspect because it's weighted. However, their graphs speak for themselves.

As to the cost in Sweden, I've come across figures of $700 per lens. It seems a believable figure and it's quite extrordinary that Photodo should provide this valuable resource completely free.

A $700 on-cost would be of course a major obstacle for any manufacturer trying to compete in a global market. However, Photodo is a small office testing relatively few lenses. MTF testing on a massive scale in an industrial context would involve industrial robots and streamlined processes. Add to that the fact that wages in China are considerably lower than in Sweden, you're probably going to come up with an additional cost of $50 per lens, a cost which could be borne by the premiums on Grade A and B lenses.


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Then there is another headache for the manufacturer. Customers comparing their MTF results and demanding their unit match the best sample curve they can find. Not only would this make your lenses even more expensive, but it is also silly as the MTF curve can detect variations that cannot be seen in the image. Amateur MTF "experts" are not worth the manufacturer's time.


This is a complete red herring. In the early 1980's, I bought a pair of Celestion SL600 loudspeakers. They shipped with individual frequency response charts. I don't know for sure if this was a scam and the charts just  theoretical, based on the design rather than the actual speaker, but the chart of the left speaker was in fact different from that of the right speaker, indicating they were real tests.

Did I buy myself a sound level meter and build myself an anechoic chamber so I could test whether the left chart was really different from the right chart? Of course I didn't. I've got better things to do with my time. And so have most people who buy lenses.

Providing individual MTF charts for lenses is really about transparency. Joe Bloggs is not likely to have the means or the inclination to question the veracity of the MTF charts, but reviewers like Photodo, or even Popular Photography, do have the means.

The current situation is that only Zeiss and Leica provide MTF charts for real lenses, on their websites. Whether or not individual Leica or Zeiss lenses have shipped with an MTF chart specific to the that lens is not clear to me. However, it does seem clear that Canon's published MTF charts for all their lenses listed in their Lens Work books, and on the USA website, are all theoretical.

Even if the cost of producing a set of real MTF charts for a particular lens is an astronomical $700 in Japan, one can't help wondering why Canon do not give us a set of MTF charts for even a 'typical' real lens.

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The current system is good. If the average quality of manufactured lenses where really as random as this thread suggests, then there would be a lot more complaints than you see here. You have a better chance to get a good lens than you do a bad one.


No! Another red herring! There are many lenses out there that have sub-optimal performance but the owners are just not aware of it. It's only the few 'fanatics' on forums such as this who are aware that a problem exists. If you haven't got something else to campare with, or are not even inclined to do such a comparison, you're going to be blissfully ignorant.

If Mark's first copy of the 24-105 was the one without the flare problem, he wouldn't be aware that another copy with the flare problem was actually sharper.
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Anon E. Mouse
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« Reply #39 on: April 23, 2006, 10:13:33 AM »
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MTF testing on a massive scale in an industrial context would involve industrial robots and streamlined processes. Add to that the fact that wages in China are considerably lower than in Sweden, you're probably going to come up with an additional cost of $50 per lens, a cost which could be borne by the premiums on Grade A and B lenses.

And how do you come up with a $50 per lens number? I would be interested in how much you would think developing and implimenting a robotic MTF line would cost? Not forgetting that the data needs to be printed and packaged with the lens. You also need to know than a $50 increase in manufacturing, does not translate into a $50 increase in product price. You need to calculate the interest on that $50 that piles up as the product sits in stock (or rather how long it take for the manufacturer take to repay the investment made in that product). In maufacturing today, engineers worry about shaving off fractions of a penny to keep prices down. Adding $50 to each product at manufacturing is huge!

Currently, manufacturers sample products in a production run with MTF curves. Why change that system which on the whole works well.



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Joe Bloggs is not likely to have the means or the inclination to question the veracity of the MTF charts

But if Joe's chart is not the same as Michael's chart of the same lens, he will complain and demand one like Michael's. And with the internet there is a good chance there will be lots of charts to compare. Since very few understand how these numbers translate into images, people are going to force the manufaturers to produce at the level of the best lenses (at least as the MTF curve is concerned) off the line which translates into higher prices or manufacturers dropping lenses and maybe going out of business.

Image quality is subjective. The MTF does not indicate a lens will make good images, but simply its response to spacial frequency. Manufacturers still take images with the lens at the end of the day to make sure the lens works. MTF is more of a guide to what is wrong, rather than what is right.

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No! Another red herring! There are many lenses out there that have sub-optimal performance but the owners are just not aware of it.

How many? Any proof of that would be welcome.

Also your logic is a little strange. You think the owner is actually gettting bad images, but he does not know it? Can't he just look at his pictures and see? Or are you saying that even if someone is happy with the lens they have, they should be careful because there could be one better?

Optics is one area of consumer goods were you get what you pay for. This is why some seemingly similar products are different prices. Not all 50mm lenses are the same and the price reflects that. Sure, sometimes there is a lemon, and sometimes the designers goof, but on the whole, the quality of the products are reflected in the price and the chances are you will buy a good sample.

FYI, returns and defective products cut into profits. Manufacturers understand this more than most consumers realize. And since margins in this business are very tight, there is little room to have products returned. It is far more cost effective to build a good product than a bad one.
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