petego4it Loc: NY

How much variation from sample to sample should one expect in a particular lens? Do brand name manufacturers have tighter and more consistent quality control? How to truly test a lens when it is new and still returnable to be sure it is "up to snuff" and can do what the reviews say it should?

gvarner Loc: Central Oregon Coast

When you get the lens and test it do you want to do an objective lab-controlled technical test or just grab a few shots of different things so you can make a subjective evaluation before returning it?

jeep_daddy Loc: Prescott AZ

You ask difficult questions to answer. First, brand name manufacturers in my opinion do have tighter quality control. This is why they are more expensive. There are some 3rd party lenses out there that are sharp and do focus well, but there are many that aren't very sharp and that don't focus well with certain cameras. I've read many reports that "x" lens isn't very sharp or that it's hunting when trying to focus. Many people report that "x" lens needed to be sent in to have it's firmware updated. I've got a lot of friends that bought the Tamron 150-600mm lens when it first came out. Everyone seemed to be happy at first, but when I bought the new Canon 100-400mm lens and a few others bought the same lens, all (and I mean ALL) of those people have either sold or put that Tamron lens in the closet in lue of the Canon 100-400 even though the Tamron has a little more reach. That being said, I can tell you this too, the Canon 100-400mm lens is the most difficult lens Canon has for them to assemble. This is in one of Canons reports. They are very intricate and complicated and precise. That is just one example.

As far as testing lenses in the real world goes, about the only thing you can do it rent them for a couple of weeks or more and see for yourself. I can attest to the fact that you can't simply put a lens on a camera and in one day figure out that it's a good lens or not. The same goes for a new camera body. It takes some adjusting in your picture taking style to find the best way to use each different lens and body. Just about any lens you buy, if you buy it from a brick and mortar store, can be purchased and returned within 30 days. It's a little more costly to return products that have been purchased on-line since you usually have to pay for return shipping and insurance.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Shot with it. But in Live View and using the mirror and PDAF.

A lens with questionable image quality is pretty easy to spot. Wide angle lenses seem to be more susceptible - often a very slight decentering will really screw up image quality - in focus in one corner of the frame and really awful at he opposite corner - as an example.

bpulv Loc: Buena Park, CA

Besides taking pictures of different types of subjects in different lighting situations and at different focal length settings, you could use a lens testing chart and look at the resolution in the center and at each corner and compare the results of multiple lenses (different brands or models of the same focal length range) to each other. Make sure that you have the camera on a tripod and manually focus the lenses using live view before each test shot. That will insure that the results are not skewed by any body to lens autofocus mismatch.

CamB Loc: Juneau, Alaska

Is this really a problem? How many times you have bought a quality lens from a major name and had problems with it? In 50yrs and many lenses I have never bought a bad lens from Nikon. A year ago, after reading UHH posts about fine tuning lenses, I began too get nervous about mine. I did the lens tests mentioned on all eight of my Nikon lenses, some going back 20 yrs. and others much newer. Every one passed with flying colors and needed no adjustment. Just don't worry about it. Buy the lens and go take pictures. On the very off chance there is a problem, you will know soon enough.
...Cam

rook2c4 Loc: Philadelphia, PA USA

One would need to acquire a large quantity of the same lens, run detailed comparison tests between them and then publish the resulting data... I can't imagine anyone would want to invest time and money for such a project. Even if there was someone crazy enough to do it, it would still be difficult to determine how your lens fits with the results unless you ran tests on your lens identical to those executed by the original tester for proper data comparison. And after all that, if you have determined the performance of your lens copy is subpar, what then? Keep replacing it until you feel confident that you have found a good one?

As CamB said: "Just don't worry about it." If you are satisfied with the results you are getting from your copy, that's all that really matters.

bpulv Loc: Buena Park, CA

The first day I attended Brook's Institute of Photography in 1965, the instructor examined every student's lens for their 4 X 5 view camera. He looked at my three-day old new Schneider Symmar lens and saw a bubble in one of the elements and told me to exchange the lens; which I did. Even individual top of the line lenses can get past quality control.

In today's high volume manufacturing processes, both in-process and final inspection is done by representative sampling, not by 100% inspection of every attribute of each and every lens. That means only a relatively small portion of "units of product" are inspected for various attributes.

A part of every sampling plan includes the AQL (Acceptable Quality Level) for that inspection point in the overall inspection process. The AQL is a number that represents the mathematical probability of failures in a given population containing many units of product. For example, an AQL of 4.0 means that for a specific sample size from a specific large population that 4 or fewer failures will occur in the large population. The sample size may only be 10% or less of the entire population depending on population size and AQL. In other words, unless their is a 100% inspection of every attribute of every product, at every step in the manufacturing process, there is some possibility that defective units of product will pass every inspection and yet fail out of the box.

If you are buying an expensive camera body or lens, you need to carefully inspect and test every product you buy.

Stan Gould Loc: La Crosse, Wisconsin

The selective final inspection of lens by the manufacturers seems to be another reason to look for a refurbished lens, all of which are inspected prior to sale.

petego4it Loc: NY

Thanks much all! I too had thought that major brand selection would guarantee quality to the level of the pro lens reviews for lenses. Not necessarily so however. Hence the question. One easy test is to use a bright light and manually open the aperture peering in from either end. Doing this in 2 brand name lenses I have I found dust inside. It's the least one should do with a new lens and periodically later too. I have (so far) not used test resolution charts but did gradually learn over 50 years of shooting to have favorite lenses for certain situations. Including color clarity too.