[Dewman]

Over the past few years, I've realized just how different the IQ can be between two "identical" lenses. Case in point: I've had at least
10 DA & DA L18-55mm lenses, with varying differences in image quality. I have kept one that is amazing in it's sharpness and color rendition. It is far, FAR superior to every other one of them I've owned and used. I realize that this is a fairly common case with just about all lenses, but the difference between my keeper and the others is astounding. It's my 'go-to' lens for almost all my still life photos and even for occasional landscape shots. I might mention that it's the WR version, for whatever difference that might make.


Just recently, I acquired another supposedly "identical" copy of a favorite of mine, a Tamron 28-200mm lens. Just for S&G's, I attached the new Tamron and went for a walk around the neighborhood and took a few shots. I came back home, downloaded them and was shocked! They weren't even close to what my old standby was capable of. So, I took my old favorite, took the same walk and shot the very same scenes that I had just shot with the newbie and WOW! My suspicions were immediately confirmed. Not even in the same ballpark! The sharpness on my old standby is on the order of a good 8.5 - 9, the newbie would be doing good to rate a 6 or better. I can see why some lenses don't get a very high recommendation. I love my "good" Tamron and it has provided me with some excellent images over the years, but this other one will have a new home soon.


Why do you suppose this is? Bad QC? Poor handling by previous owners? Or, it is just "the way it is"?

[johnhilvert]

Over the past few years, I've realized just how different the IQ can be between two "identical" lenses. Case in point: I've had at least
10 DA & DA L18-55mm lenses, with varying differences in image quality. I have kept one that is amazing in it's sharpness and color rendition. It is far, FAR superior to every other one of them I've owned and used. I realize that this is a fairly common case with just about all lenses, but the difference between my keeper and the others is astounding. It's my 'go-to' lens for almost all my still life photos and even for occasional landscape shots. I might mention that it's the WR version, for whatever difference that might make.


Just recently, I acquired another supposedly "identical" copy of a favorite of mine, a Tamron 28-200mm lens. Just for S&G's, I attached the new Tamron and went for a walk around the neighborhood and took a few shots. I came back home, downloaded them and was shocked! They weren't even close to what my old standby was capable of. So, I took my old favorite, took the same walk and shot the very same scenes that I had just shot with the newbie and WOW! My suspicions were immediately confirmed. Not even in the same ballpark! The sharpness on my old standby is on the order of a good 8.5 - 9, the newbie would be doing good to rate a 6 or better. I can see why some lenses don't get a very high recommendation. I love my "good" Tamron and it has provided me with some excellent images over the years, but this other one will have a new home soon.


Why do you suppose this is? Bad QC? Poor handling by previous owners? Or, it is just "the way it is"?

It's worth trying micro focus adjustments before a final evaluation.

Try focusing and taking some images with live view which should eliminate the possibility of focus adjustments as well.

[clackers]

.

Try focusing and taking some images with live view which should eliminate the possibility of focus adjustments as well.

Yep. *Then* it comes down to the lens itself, not its pairing with the AF sensor.

[Alex645]

The optics in zooms are more complex and compared to primes, I believe it is not uncommon to see a greater variation from one copy to the next. More elements in more groups, more moving parts and potential for fungus or dust, can easily affect IQ. Yes, it could have become damaged due to physical trauma, but it is also possible that it was within tolerances of the manufacturing process.

[Not a Number]

This is why back in the day Modern/Popular Photography would obtain at least 3 lens from sources other than direct from the manufacturer for their in-depth tests.

This is why Director / Photographer Stanley Kubrick would get ten copies of a lens and try each one out before selecting which one to keep.

[WPRESTO]

As noted above, modern zoom lenses have 10 to 15 elements. Each must be ground to exactly the same thickness & curvature, each one perfectly spaced, each one perfectly centered. Tolerances on the order of wavelengths of light. An ultra-precision manufacturing challenge that will produce probably thousands to tens of thousands of copies. Small wonder some turn out "perfect." some dreadful, many not quite as good as we'd hope. I'm always happy to find multiple tests of the same lens by totally different, independent sources, at least you can get an idea of how good the lens can/should be.

[pathdoc]

I think my wife would kill me if I tried Kubrick's approach - not to mention that giving the bad ones back isn't easy where I live, as it involves regular homage to the postal service.

[atupdate]

Are you comparing the exact same Tamron models? There are older versions (72mm filter size) that look almost identical except for a marking used for "Closest Focusing" (See link below). One is supposed to be optically better than the other. I have 3 versions of the Tamron 28-200 but have never done a side by side test.

Tamron 28-200 differences

I don't doubt your observations between the Tamron or DAL lenses. No assembly process is perfect and variation is expected. I love my Tamron 28-200's (One has a Promaster badge) and have one attached to my camera as the default.

You might find this link interesting, as it shows when the various Tamron models were discontinued.
http://www.tamron.co.jp/en/data/lenses/list_dis.html

Tim

[Odinz]

I have noticed this on even older simpler lenses. Sometimes it's more severe and noticeable than others, others you'd need to pixel peep to really see any differences. It's just the nature of the optics, tolerances being what they are, if the right element isn't in the right position, either through manufacture or use it can effect the lenses performance. And if the lens has ever been worked on, all bets are off.

[Na Horuk]

Its probably factory tolerances, and then QC. QC should catch the worst ones, the bad and broken ones.
And I think this is why "premium" lenses like Zeiss and Leica are so good. Sure, good designs and materials, but it is also important to have really tight factory tolerances and high QC standards. This is also why things get expensive, because a difference of 1mm placement or a small difference in the material consistency can be difficult to detect, but will still have an optical impact.

[WPRESTO]

Its probably factory tolerances, and then QC. QC should catch the worst ones, the bad and broken ones.
And I think this is why "premium" lenses like Zeiss and Leica are so good. Sure, good designs and materials, but it is also important to have really tight factory tolerances and high QC standards. This is also why things get expensive, because a difference of 1mm placement or a small difference in the material consistency can be difficult to detect, but will still have an optical impact.

1mm misplacement of a lens could be catastrophic. Tolerances should be on the order of hundredths to thousands of a millimeter.

[pacerr]

Over the years I've had the opportunity to compare three 'identical' lenses of the same type on a number of occasions. Specifically: the DA 18-55, DA 50-200, DA 55-300 and Tamron AF 28-200, AF 24-135 and AF 10-24.

In every case I've noticed that two would be of 'nominal' quality and one would be noticeably superior in one or more characteristics. In most cases the differences wouldn't have been evident without direct comparison and the 'lesser' lenses would have been accepted as typical of the category. Who's going to expend the time and resources to search for the best of a consumer-quality item?

Categorically, individual consumer-grade products are little affected by QA processes other than periodic line sampling. At that cost-level QA is more devoted to tooling and final 'fail to function' tests solely by economic necessity. But there's nothing to prevent everything coming together 'just right' for an individual item where a 1-of-1000 example is produced that's as good as its design, assembly and materials allow. Being tarnished by reputation and expectations, that superior item is normally overlooked unless it happens to fall into the hands of an interested and experienced user.

There's always going to be a few items of any type that don't make it past the assembly line for some reason. High end items will naturally group more toward the positive side of the quality bell curve owing to the resources ($$) devoted to the product. Consumer quality items will be spread across a much broader quality bell curve but a few will still standout within the limits of the design.

I have a DA 50-200 that pairs up with K200s that's simply amazing within the limits of their respective design - but that still reflects the functional limitations of a DA-grade kit lens. Consequently it never gets used owing to the more capable lenses available to me and I really ought to pass it on to someone that would value it as a superior example of a kit lens.

[Dewman]

Here are two shots with what are supposed to be two "identical" Tamron 28-200mm lenses. Even with my poor eyesight, the difference in IQ is quite evident, don't you think?

[WPRESTO]

Yup, The two of the truck are sharper.

[normhead]

Over the past few years, I've realized just how different the IQ can be between two "identical" lenses. Case in point: I've had at least
10 DA & DA L18-55mm lenses, with varying differences in image quality. I have kept one that is amazing in it's sharpness and color rendition. It is far, FAR superior to every other one of them I've owned and used. I realize that this is a fairly common case with just about all lenses, but the difference between my keeper and the others is astounding. It's my 'go-to' lens for almost all my still life photos and even for occasional landscape shots. I might mention that it's the WR version, for whatever difference that might make.


Just recently, I acquired another supposedly "identical" copy of a favorite of mine, a Tamron 28-200mm lens. Just for S&G's, I attached the new Tamron and went for a walk around the neighborhood and took a few shots. I came back home, downloaded them and was shocked! They weren't even close to what my old standby was capable of. So, I took my old favorite, took the same walk and shot the very same scenes that I had just shot with the newbie and WOW! My suspicions were immediately confirmed. Not even in the same ballpark! The sharpness on my old standby is on the order of a good 8.5 - 9, the newbie would be doing good to rate a 6 or better. I can see why some lenses don't get a very high recommendation. I love my "good" Tamron and it has provided me with some excellent images over the years, but this other one will have a new home soon.


Why do you suppose this is? Bad QC? Poor handling by previous owners? Or, it is just "the way it is"?

This is why I keep saying to folks, the fact that your <put the name of your worst lens here> sucks does not mean, it's a bad lens. It doesn't mean you should be telling others not to buy it if it meets there needs in other ways. There is nothing to my mind worse than coming on the forum and pushing people on to lenses that are not the focal length for what they do, or meets more than the requirements they need. 90% of the forum try to sell more than the person is asking for.

My copy of the 18-250 is terrible, but, others are quite happy with it. The thing is, if you get a good 18-55, you've got a great lens. One of the reasons for buying Pentax is it's better than you get on other brands. If your needs are light, you might luck into a great lens without spending a lot of money. Sometimes it's worth the gamble.

The absolute worst thing about the forum is people trashing all copies of the bad lenses they've owned. Everyone seems to think their world is the whole world. In my lens comparisons, those "bad" lenses always get a few votes. Even between the good and bad lenses, comparing straight up on the same image, you don't always get a clear winner in terms of how much people like the good one and the "bad" one. What a cheap lens gets you is the opportunity to get the best possible image taken at that point in time and space, without laying out a pile of money. If you got a good copy and all it's strengths line up, it may blow away your $5000 lens someone said you needed to get nice bokeh.

More expensive lenses often have better build quality. If you don't use your camera enough to risk breaking the lens, or wearing it out, you don't care about that. Some lenses feel a lot smoother or are better damped. If you just want an image or two a couple times a month that's irrelevant. I swear, a lot of the time this place is worse than a camera store. someone comes in and asks for a good cheap walk around lens, and someone will recommend the 16-50, without fail. I've never seen a camera store salesman trying to up-sell prospective buyers, like the some people on this forum do.

I used my *ist 18-55 and Sigma 70-300 for four or 5 years, without feeling the need to upgrade. And I was teaching photography at the time. Yet I see all these newbies pushing people who aren't even pros into expensive glass. It can be distressing. There is absolutely nothing wrong with starting slow and working your way into what you might need.

If there was one piece of advice I'd give people starting out on the forum, it would be, most of these people aren't pros, most of their advice is suspect.

Some DA 18-55










One of those images sold for over $200, as a 20x30 canvas print. Just how much can you ask from a lens? It paid for itself in one sale, and put $50 in my pocket. I'd love to have more lenses capable of that.