Lens variation and remedy

[jeremy_wakefield]

<p>Hello. I've been looking at lenses recently and read a number of reviews and posters' experiences on a few sites. Again and again, the advice for many lenses is to buy from a reliable dealer who will accept returns so that if you get a bad copy you can send it back.</p>

<p>Now I can understand that there are bad lenses around but I'm betting there isn't as many as people imagine. I'm also querying the logic of sending bad samples back to the shop until you get a good one. I've read of people repeating this multiple times before they are either happy or give up!</p>

<p>Surely the best procedure would be take whatever lens you get sold, and if there's an issue send it back to Canon and get them to recalibrate it. I know Canon get it wrong too but even if you had to send it back a couple of times you'd end up with a lens that was the best of it's kind.<br>

More altruistically would avoid the same bad lenses circulating on the refurbished market. </p>

<p>What's wrong with my theory?</p>

[john tonai]

<p>Nothing, because the majority of the time people say they got a bad lens, the problem can be traced to the photographer's methodology</p>

[jeremy_wakefield]

<p>I'd say you're probably right, John. But even if you did have a bad lens would it not just be better to get Canon ( or whoever makes it ) to sort it?</p>

[bobatkins]

<p>Depends. A lens may be within spec, yet still not be as good as another sample. Canon (or Nikon etc.) aren't in the business of making a perfect lens for you, just lenses that meet their performance specifications.</p>

<p>They will, of course, repair anything with an obvious defect.</p>

[phule]

<p>[[Now I can understand that there are bad lenses around but I'm betting there isn't as many as people imagine]]<br>

<br>

<a href="http://www.lensrentals.com/blog/2013/09/there-is-no-perfect-lens">http://www.lensrentals.com/blog/2013/09/there-is-no-perfect-lens</a></p>

[ruben leal]

I own an EF 28-135mm f/3.5-5.6 lens that is so misaligned that half side of the image is in focus while the other half is

quite out of focus, kind of a lensbaby. Sent it to CPS for yearly cleaning, and they charged me to correct the alignment

and a problem with the IS, took them almost a couple of months to get the IS spare parts sent to Mexico. Finally I got the

lens back with a new feature: now it was a f/5.6 fixed max aperture lens, and the EXIF shows all the images taken at

135mm, no matter what was the actual focal length. Half the image still is out of focus, but not as bad as it used to be.

Sent it back to CPS and they said alignment was within spec, saying they connected a loose connection to solve the

aperture and EXIF info problem, but not correcting the optical problem. Apparently the cable got loose again, as it jumps

from f/3.5 to f/5.6 and back when moving the lens.

 

How many times would you send back a lens for that kind of answer, not only from a Canon Service Center, but the CPS

Service Center? I got tired, used it as a pretext to buy a 24-105mm L lens, and lent the 28-135 to my brother...

[jeremy_wakefield]

<p>Interesting link, Rob. Thanks. There's a lot of information there that makes sense.<br>

I realise the lens needs to be within a certain range and I'm pretty sure most of the stuff you read about "bad copies" is not as it seems. Personally I'd not worry too much as long as in real world shooting the lens performs well enough.<br>

Sad to hear cases like Ruben's though. I have to say I've only twice sent a lens back to Canon, also CPS. On one occasion they replaced the lens, but sent it back rattling around a large box with no protection at all - fortunately it worked all right. <br>

My worst experience was with Nikon UK and a D800 which was an absolute farce, but that's another story.</p>

[JDMvW]

<p>The only place I know of that even approaches the topic of <em>sampling</em> of lenses is the LensRentals site referred to: http://www.lensrentals.com/blog/category/technical-discussion/lensoptics and other points at the same place.</p>

<p>Most lens tests are done on individual lenses because none of the testers can afford to assemble a statistically significant sample of any given lens.</p>

<p>I think Bob's point is just right. There are differences among samples of a particular lens, but they are unlikely to be "out of specification" and will work well enough for most of us. The worst today is probably going to be better than <em>most</em> older lenses assembled on a bench somewhere.</p>

[Robin Smith]

<p>This seems to me to be more related to the kind of photographer you are. One person I know will not buy a new filter without opening and personally examining it and then only accepting one that meets their perfection standards. This dismays and annoys the store assistant, but she persists. Some people do indeed check every lens in sickening detail before accepting it. I wager it makes zero difference to the photos they end up taking. Of course, this is different to trying a lens and deciding that its performance overall is not what you want, but the mind-numbing idea of finding a "good copy" seems to me to be very much related to the way your mind (and emotions) are. Personally I use a lens for a couple of days and see if I am happy. I have tried the odd A/B test with different lenses because there seems some purpose to this, but I am not in the business of examining manufacturing variations as a matter of course. My advice - don't worry, there will be some variation, but most observable differences are down to user error/technique. </p>

[jeremy_wakefield]

<p>So. We're agreed that this pursuit of a "good coy" is hokum and that if the lens is indeed out of spec the manufacturer could indeed recalibrate it so that it is within spec?<br>

This is pretty much my theory. There's a site as you all know where there are endless discussions on the angst of finding that "good copy" of any particular lens.<br>

Although they do test their lenses, lens rental companies do have a sense of humour.<br>

Look<br>

http://www.lensrentals.com/blog/2012/03/hammerforum-com</p>