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Buying a new lens...how do I know I have a good copy?

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Pastor Vic

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I am just getting into the m43 world and am hearing quite a bit of chatter about bad and good copies of m43 lenses. When I get my new system, how do I know if I have a good copy or not? If I have a bad copy, what do I do?
 
You can use a newspaper tacked to a wall (tripod mounted camera) or find a brick wall...you can pretty much figure out if your lens has distortion or if it is soft in the corners or center by taking a series of shots at all apertures. Start wide open and close down by one stop each time. Download the shots to your computer and look at them...you will find any shortcomings very quickly. If the lens is not up to your standards, go back to the dealer and exchange it for another...repeat the testing until you find one that you like. Good luck.
 
Pastor Vic said:
I am just getting into the m43 world and am hearing quite a bit of chatter about bad and good copies of m43 lenses. When I get my new system, how do I know if I have a good copy or not? If I have a bad copy, what do I do?
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If you cannot readily see a problem then you have no problem. If the problem is obvious then it should be returned fo exchange (not repair).

Some lens owners are perfectionists and test their new lenses rigorously and complain.

Myself I am not critical enough or lack the skills to observe lens problems and live happily not knowing.

As the owner of many lenses I have not noticed any bad copies of lenses bought new (from any manufacturer). But that is my problem and I can live with it.
 
LMNCT said:
You can use a newspaper tacked to a wall (tripod mounted camera) or find a brick wall...you can pretty much figure out if your lens has distortion or if it is soft in the corners or center by taking a series of shots at all apertures. Start wide open and close down by one stop each time. Download the shots to your computer and look at them...you will find any shortcomings very quickly. If the lens is not up to your standards, go back to the dealer and exchange it for another...repeat the testing until you find one that you like. Good luck.
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ie: drive your dealer wild with excitement (grin) Lucky my standards are quite low, am plain lucky, or simply never get around to proper testing .... ;)

--
Tom Caldwell
 
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Now that front/back focus is no longer an issue with CDAF systems like Micro 4/3, there are 2 major issues I test for when I get a lens:
  1. Mechanical/electrical (does the lens make unintended noises, have aperture/focus motor issues, or fail to communicate with the body)
  2. Decentered elements. I discussed about it here: http://www.dpreview.com/forums/post/55936937
I also check for debris inside the lens, not because of image quality but because of the hit to resale value if there's a big piece stuck inside.

I also found there can be significant sample variation in sharpness in the same lens model, but this is not something that's immediately apparent unless you get really bad copy (uncommon).
 
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Pastor Vic said:
I am just getting into the m43 world and am hearing quite a bit of chatter about bad and good copies of m43 lenses. When I get my new system, how do I know if I have a good copy or not? If I have a bad copy, what do I do?
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You know what they say about pornography? It operates similarly for lenses. ;)
 
Don't believe everything you read on the Internet.
 
Hi

I test for obvious quality issues with the brick wall and simple decentering tests. I have never had a faulty lens as such. I do read up on the lens I am buying first so I know what to expect regarding sharpness and other qualities. There is no point expecting a lens that is known not to be sharp, (but is bought for other qualities) to be pin sharp for instance.
 
Pastor Vic said:
I am just getting into the m43 world and am hearing quite a bit of chatter about bad and good copies of m43 lenses. When I get my new system, how do I know if I have a good copy or not? If I have a bad copy, what do I do?
Click to expand...
It's not just M43 lenses, Getting a bad copy of anything happens all the time. Used to be that grinding the glass to make a lens element was done by hand and no two elements were exactly alike and the same went for the rest of a lens as well. Now, everything is computerized and most of the fine work is done by robots, so in theory, every part of every lens should be the same but you might get one that was done on a Monday by someone recovering from a rough weekend or one that slipped past on a Friday when the tester was paying more attention to his or her smartphone to plan the weekend's events.
 
bs1946 said:
Pastor Vic said:
I am just getting into the m43 world and am hearing quite a bit of chatter about bad and good copies of m43 lenses. When I get my new system, how do I know if I have a good copy or not? If I have a bad copy, what do I do?
Click to expand...
It's not just M43 lenses, Getting a bad copy of anything happens all the time. Used to be that grinding the glass to make a lens element was done by hand and no two elements were exactly alike and the same went for the rest of a lens as well. Now, everything is computerized and most of the fine work is done by robots, so in theory, every part of every lens should be the same but you might get one that was done on a Monday by someone recovering from a rough weekend or one that slipped past on a Friday when the tester was paying more attention to his or her smartphone to plan the weekend's events.
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and yet, at the times where lenses were made by hand, the term bad copy didn't exist. There was no such thing as bad copy and I can only guess that QC was much better then.

There maybe some truth in having some "bad copy" lenses although I haven't seen even one during my 50 years of experience and I had close to 100 lenses.

I have the impression that in the era of digital,photography people just became too obsessed up to the edge of paranoia about ultimate quality which is ridiculouse because in most of the cases, the "bad copy" is the photographer himself.

Moti

--
http://www.pixpix.be
http://www.musicalpix.com
 
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You cannot know easily whether you have a mediocre, good or outstanding copy... but you can detect a common defect: uneven sharpness due to something not being placed correctly.

Take a picture of a flat subject, head on. People often use a brick wall for that. Then turn the camera upside down and take the same picture. After rotating back on the computer, compare both pictures. They should look identical. If say one has a softer bottom left corner and the other a softer top right corner you know the lens is bad (often called a decentering problem).

This type of defect is unfortunately not uncommon. I have had to return a few lenses with this problem in the past. Getting them fixed is in many cases hopeless as the manufacturers don't test for this problem and will simply return the lens as being within manufacturing tolerances. Exchanging for another copy is the most viable solution.
 
Nobody had ever used the word "copy" to apply to lenses until a bunch of gearheads gathered in a forum, just saying. If you take pictures with your lens and you like what you get, you have a good lens. If not, then you don't.
 
QC was better then but they were not mass produced items and in real terms were more expensive.

They were also 'less ambitious' designs with mainly primes and 2 or 3x zooms, at least in my experience which goes back to the 1970s.

Finally the standards were generally lower and it wasn't as easy to pixel peep.

People were generally producing modest prints or viewing slides at a sensible viewing distance
 
What do you imply? That there is no lens sample variation? If so, you should really do a reality check from time to time.
 
honeyiscool said:
Nobody had ever used the word "copy" to apply to lenses until a bunch of gearheads gathered in a forum, just saying. If you take pictures with your lens and you like what you get, you have a good lens. If not, then you don't.
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It is not because someone does not notice a defect that it isn't there.

Example: One of the bearings on my car broke. (This happens after a lot of mileage, it is normal wear.) I could hear it making noise especially on the highway. My wife could not hear it. What does this mean? Because it was "my" car it was broken and if it had been "my wife's" car it was not broken? That's silly, isn't it? Well the same applies to lenses as well. When you have a soft corner the lens is broken. When you have a soft corner but you don't notice, perhaps because you always take pictures where the corners are out of focus, the lens is still broken. Who owns the lens and whether he or she likes the pictures or not does not affect whether a lens is broken or not.

Whether a non-broken is "really good" is another matter. Some copies are sharper overall than others but all can be "good enough" with some being just good enough, others really good and still others stellar. Whether the owner considers it good is subjective. Whether a lens is defective or not is not subjective.
 
photofan1986 said:
What do you imply? That there is no lens sample variation? If so, you should really do a reality check from time to time.
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Indeed, after having spent 30+ years in design and manufacturing of complex technological products, I must have no clue regarding the role that component and manufacturing tolerances play in end items meeting or not meeting both design and production test specs.

I don't believe for one minute that the lenses in question are simply assembled, dropped in boxes and shipped. On the contrary, a complex technological product like these certainly must pass rigorous production tests before they are shipped to customers.

The fact that an armchair "quality inspector" imagines they can devise standards of their own which may or may not exceed those of the manufacturer, doesn't change the quality of these lenses one bit.
 
LMNCT said:
You can use a newspaper tacked to a wall (tripod mounted camera) or find a brick wall...you can pretty much figure out if your lens has distortion or if it is soft in the corners or center by taking a series of shots at all apertures. Start wide open and close down by one stop each time. Download the shots to your computer and look at them...you will find any shortcomings very quickly. If the lens is not up to your standards, go back to the dealer and exchange it for another...repeat the testing until you find one that you like. Good luck.
Click to expand...
If you do these tests, you must be certain that your lens is exactly parallel to the target surface and that all the points you are comparing are the same distance from the lens, not easy to do unless you are in a laboratory.
 
So that is your "proof" that lens variation does not exist? Then I guess ignorance is bliss.
 
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