Lenses and Optics

Inspecting an ‘In Spec’ Lens

Published November 14, 2013

I’m going to open a can of worms today.  I’ve been getting more and more emails from people telling me the same story that goes like this:

I’ve got this lens. It’s awful. I’ve sent it in for adjustment and the service center tells me it’s ‘in spec’ and nothing is wrong with it. Am I crazy?


Second only to the dreaded ‘impact damage – warranty void‘ statement, the ‘lens is in spec’ statement seems to be some factory service center’s answer to far too many complaints. Don’t get me wrong, sometimes there is impact damage and the warranty should be void. But I can’t think of any reason why this seems to happen only to certain brands and never to others. Similarly, lenses a customer thinks are bad can be ‘in spec’. The problem is, since the factory service center doesn’t have to tell us what ‘in spec’ means, it’s open to a lot of abuse.

Now before I go further, let me say that I feel the service center’s pain, too. Most of those emails I get are accompanied by some useless JPEGs. Maybe 1 person in 10 who emails me actually has taken images that would indicate if there was a problem or not. So I’m certain the techs at the service center become a bit cynical over time.

So if you think a hand-held autofocus image, an ISO 6400 image, or a picture of some isolated object right in the center of the image is helpful in deciding if a lens is OK, then you aren’t allowed to read this post. Instead read about how to test a lens, how to check for decentering, or what a lens with a tilted element looks like. Then you can come back and read this.

An Example

First of all, I’m not going to mention what lens or company this example is taken from. The reason is simple – I’ve got plenty of similar examples (over 100 actually) with other lenses and other factory service centers.

What we have here is a high-quality, fairly expensive zoom lens. It was sent to factory service because it had much lower resolution on the left side than the right. It came back looking the same. The second time it came back better at the wide end, but worse at the long end along with a note saying it had been tested and was in spec. The third time it came back no better with a note that it had been tested and was in spec. We didn’t see much sense in trying a 4th time.
I won’t bore you with optical bench, lens test projector, or Imatest results for the lens (we did them, but I want to keep this simple and they aren’t necessary). I’ll just show you images taken of an ISO12233 test chart.  I like this chart because it lets us look at resolution in the center and all 4 corners in one shot, if done correctly.

Here’s a picture of the chart, in case you aren’t familiar with it:


The lens that came back from factory service for the 3rd time was OK in the center, so I’ll just show you close-ups of the 4 cross-shaped resolution charts in the corners. Here are the corners at the wide & zoom ends of the zoom range.


Four corners at widest zoom, ‘in spec’ according to factory service



Four corners at long end of zoom, ‘in spec’ according to factory service


To make sure you have an idea of how bad this ‘in spec’ lens is, in the image below I’ve put the top two corners at the long end from the ‘factory in spec’ lens with the top two corners of another copy of the lens taken off our shelf. Again, because someone who doesn’t read the whole article is bound to say it – these shots are all focus bracketed and the best image used. Autofocus has nothing to do with it – this is purely optics.


Top two corners from the factory ‘in spec’ lens above; top two corners from an off the shelf lens below.


Like we all learned from Sesame Street, one of these things is not like the other. According to the factory service center, they are both fine. But if I sent that ‘in spec’ lens out to one of my customers, I would have one less customer.

I talked Aaron into opening this lens up and adjusting it in-house. Adjusting it involved removing the mount and making some 17 trial-and-error adjustments to the rear group, testing after each adjustment. Then we removed the front barrel and made a half dozen adjustments at the front group, followed by taking the mount off again and making some more tweaking adjustments to the rear element. It was a several-hours long process. But at the end of the process, the lens was now within my ‘spec’ as you can see below.


Four corners at wide end after adjustment


Four corners at long end after adjustment.


It’s not absolutely perfect. If you noticed, the left lower corner at the wide end still has some astigmatism with the vertical lines not resolving nearly as well as the horizontal lines. But even that corner is much better than when it came back from the factory in spec (and is better at infinity than in this fairly close-up shot). The other 7 corners are all excellent. Maybe we could have gotten that last corner better, but my experience is that most of these lenses have a slightly weak corner at one end of the zoom range.

It’s the same lens, no new parts, just a very lengthy optical adjustment.

My point is not that we’re so great. We’re not. We’re just a couple of self-taught guys trying to figure stuff out mostly by trial and error. My point is that if some half-trained guys with a few screwdrivers and some optical testing equipment could do this, then the trained technicians at the factory service center could have done it, too. They certainly could have done it faster. In theory they could have done it better.

But in three tries they didn’t do it at all. They just told me, in writing, that the lens was ‘in spec’. They won’t share exactly what those ‘specs’ are, but in this case the picture says it all. Their specs are pretty damn low.

Let me repeat for you fanboys who are certain your brand doesn’t do this – chances are that it does. I just chose this lens because it happened to come back yesterday. I have this kind of result several times a week (out of dozens of repairs a week, mind you).

So Why Doesn’t the Service Center Do It?

I’m doing some educated guessing here, and not all reasons would apply all of the time. But here are some of them.

1. Some lenses can’t be optically adjusted. The factory has the choice of giving you a new one, telling you the one you have is OK, or randomly replacing some of the lens elements and groups and hoping that makes it better.

2. Service centers don’t have nearly as much optical testing equipment as you think they do. None of them talk openly about what equipment they have, but I’ve had a lot of conversations with techs that let slip that they don’t have certain capabilities. They have lots and lots of computerized adjustment software. But most don’t have optical benches, collimators, or even high-quality test targets. Some use lens-test projectors, which aren’t particularly accurate, but are better than nothing. Some don’t even have those. My favorite anecdote is a lens we fought with the service center over for 3 months. The last time it came back we were told their chief of optical testing had adjusted it himself. Unfortunately the chief left his memory card in the camera that we’d sent along with the lens: 62 images of a bookshelf were used to make the optical adjustments. Even when looking at a bookshelf, though, you could tell it still wasn’t right.

3. Some service centers apparently can only adjust optics for the center of the lens. They apparently don’t have equipment for off-axis adjustments or assessment. (That’s may be the case with this brand; they always seem to get the center perfectly adjusted but often send lenses back with horrid corners.)

4. These adjustments can be really, really difficult and time consuming. The techs are on a clock, expected to do a repair in a given amount of time, so they must dread optical adjustments. Or maybe ‘in spec’ just means time was up.

5. When a customer says their lens is soft, the most common problem is that they can’t tell backfocus from their back end. So the service center tends to ‘electronically adjust’ the lenses. That is fast, computerized, and works great when the problem really is backfocus or frontfocus — and that’s usually the problem. But eventually, if all you have is a hammer, everything starts looking like a nail.

6. So many people claim their lens is bad when it really isn’t, that the techs get rather cynical. I’ve gone up the food chain often enough, and have heard the surprise in someone’s voice when they say, “Oh, you really do know what you’re talking about,” to know this is true.

So What to Do?

I don’t expect my writing a blog post is going to make any factory service center rush out and make changes. But it may help some of you who are fighting these battles to know it isn’t just you. Just because you’re paranoid doesn’t mean they aren’t out to get you.

I also think that maybe, just maybe, if people ask politely with their wallets, some manufacturer will decide it will be to their competitive advantage to offer better optical services. Sigma recently got a ton of positive press when they showed the equipment they had placed in the assembly factory to test every lens before it was boxed for shipment. People want that kind of assurance.

If you run into this problem, you might ask to see the optical test results. They aren’t going to show them to you. Looking at the example above (and lots of similar examples like the ones above), I doubt they even have any. But maybe if enough people ask, in these days of lowered sales expectations, one or two companies might decide enough customers are interested in that service to provide it. Actually, we only need one company to do that. The others will have little choice but to follow along.

I think that a service center that actually sent you a printout of their optical tests, showing that your lens really did (or didn’t) meet the expected test results, would win a lot of loyal customers. Heck, the oil change place always shows me the old filter they replaced just to make sure I know they really replaced it. The service center could at least show me that they’d actually tested the lens.

Actually, I suspect there are one or two companies that already do have optical testing equipment available in their service centers, and who use it to make accurate optical adjustments. If they’d like to show it off, I’d be happy to write about it for them.


Roger Cicala


November, 2013


A Note About Who Shot John:

I knew it would happen – that people would be angry that I don’t name names. Let me be clear as to why.

First and foremost, I haven’t gone back, gathered the data on 10,000 repairs, hand sorted which ones were repeat optical repairs (because that parts not a sortable field in our database), compared that to all optical repairs for that brand, number of copies and rental weeks for each lens, etc. That’s a 60 hour job and I’m busy at the moment. But without that it would be totally unfair for me to put up a note saying ‘this manufacturer has more problems’, etc. Do I have some ideas in my head? Sure. But I’m the analytical type. I want numbers and facts before I spew off negativity.

Second, I’d really like to see changes made. Backing someone into a corner and thrashing them is certainly fun, but it rarely results in change. It usually just results in damage control and denial. If I did that today I already know what the response would be – ‘we have far superior methods of testing our own lenses, but they are secret and proprietary and we can’t show them to the public’. Given the way most camera manufacturers seem to work these days, they might change things quietly and secretly. A few years from now things might be better (or they might not). But they would never, ever let us know there had been changes, because there was never a problem.

I’d much rather that one company, having not been backed into a corner, decides it will be great marketing to show the purchasing public how they test, to provide test results when you send a lens in for optical adjustment, to get lavish praise in all the forums for that, and watch the serious photographers, who buy lots of lenses, flock to their brand. Is it going to happen? Nah, probably not. But I’m an optimist.

But for those that want to investigate what companies might be better at optical adjustments, here’s a good place to start. Look up what companies make both lenses and optical testing equipment. You’d kind of figure they’d have their own machines in their own service center, wouldn’t you?



Author: Roger Cicala

I’m Roger and I am the founder of Lensrentals.com. Hailed as one of the optic nerds here, I enjoy shooting collimated light through 30X microscope objectives in my spare time. When I do take real pictures I like using something different: a Medium format, or Pentax K1, or a Sony RX1R.

Posted in Lenses and Optics
  • A G Dorsey

    Roger you never fail to inform, entertain and reassure the greater LR community. From my very first rental I’ve never ever received an improperly “in-spec” lens. Your post contrasts the difference between providing facts ( i.e., test results) as opposed to soliciting faith (i.e., a manufacturer’s letterhead note saying “in-spec”) to a customer. I can only hope these manufacturers are as reasonable and customer-centric as LR.

  • Being an Authorized Service Center for Canon and Nikon lens we understand what you’re talking about. Because of having the proper equipment for Canon and Nikon we have no issues with their alignment. Each manufacture has their own spec and some are tighter then others, some of the aftermarket lens manufacture’s specs are a joke. We have the same issue you have with the manufacture’s we do not have lens alignment equipment for, the time to adjust without the proper equipment would not be cost effective. We send a lens in to these manufactures for adjustment only and receive it back more out of standard then when we sent it in. Just because they have the test equipment in the manufacturing plant, does not mean they have it here in their Service Center. We have the same test chart you are using, and have shown some of our lens test equipment on our website for years http://www.midwestcamera.com/lens.html . Also a note that all Authorized Service Center are lens authorized and do not have the lens alignment equipment.

  • Peter

    Have you considered opening up a service center, where we could send lenses to get them to your “in spec?”

  • Many times I saw a colleague and friend of mine, who shoots brand X (I’ll try to avoid a holy war, too) sell his glass just to buy a new one, same model. To my question why, he would answer – “Well, it’s not as sharp as it used to be”. For a couple of years I thought that he’s just imagining things. Besides, how about AF fine tune and all that jazz?… But his typical lens life never changed: buy a new lens, use it for a year or two, send it to a factory service center, get it back, use some more… sell, buy a new one. Rinse and repeat.

    About a decade later, I’ve switched to the same brand. Two years, bam! – I am sending a lens in for adjustments, and it comes back with “in spec” diagnosis, not as sharp as it used to be. Duh!

    After 3 years of struggle, I’ve switched my camera system again, to never look back. Hopefully.

    Nevertheless, your article actually describes a fantastic market niche. A totally unoccupied market niche: lens tuning lab. Let’s say, if I have a $2000 “in spec” zoom that “misbehaves”, I can sell it on eBay for $1200 and buy a new one. That’s a $800 loss (actually, more – after taxes), plain and simple. And that new lens could be an “in spec” lemon, too.

    So… I’ll be extremely happy to just send that old lens to some third party lab to turn it into a “hot rod”… but there’s no such lab.

  • Bill GM

    I heard that “in Spec” garbage from Canon on my 20D, 40D and 7D. None of which could get a focused image to save my life. Finally got a Nikon D800 and like magic I get in focus images. I lost quite a few years and much of my hair dealing with “in Spec” junk.

  • Lynn Roberts

    I would *so* be willing to pay $$$ to you guys if you were able to clean my camera (and lens, if required), and test a camera/lens combination – and do AF fine tuning. (This is tricky, as I’m sure you know, with longer lenses, or lens/TC combinations). My local camera store and independent repair person won’t do this. I have little confidence in my camera/lens manufacturer’s being able to do a decent job with fast turnaround.

    Heck – just test out a new lens for me on my body – let me know whether it should be returned/exchanged!

    My own forays into photographing test charts with long lenses left me with a giant headache. For sure I could see the issues in the lower left image (“after correction”) you posted, but when I tried AF fine tune myself, it was as bad as any trip to the optometrist: “better, or worse???” The heck if I can tell! Except then(and consistently) my images aren’t as sharp as I think they should be…

  • intrnst

    Thanks for taking the time to answer, Roger. But despite my
    divergence with your non disclosure philosophy, I can understand and respect it. Always a gentleman, sir.

  • NancyP

    I agree that saying that “every manufacturer has sloppy repair practices” is more efficacious than pointing out that single poor service incident X belonged to the CaSoNiPeMaZ brand repair facility. Dang, that made-up name sounds suspiciously like the latest pharmaceutical.

  • I worked in the cinema business for 16 years in the lens and lens engineering field. While my experience does not apply directly, it does have a good correlation with still gear.
    Additionally, I have purchased an awful lot of lenses for my present career(R&D).

    When we would buy prime lenses, primarily from Zeiss and Cooke, we would evaluate as many lenses the vendor would let us have, and choose the best, and try to make up a set with consistent sharpness, and best color match. A set might not have the sharpest lenses, but would have the sharpest set of lenses.

    similarly, what you are seeing is a set of lenses, with a selection of lenses that are exceptional. Once you have an exceptional lens, it is hard to accept an acceptable lens.

    What I can tell you about the zeiss Hasselblad glass I have seen, is not only is it mostly excellent, but it is mostly consistent. The Hassie glass of a particular type matched up with lenses of the same type very well.

    Canon and Nikon are generally very consistent, and generally very good.

    Sigma is generally less consistent, with examples as good as similar Nikon or Canon glass.

    This is where your local camera store has considerable value. Tell them when you are going to purchase a lens, and ask them to have a few to choose from. Pick the best, and let them send the rest back. You spend 10% more at a store, but you get the best of the litter.

  • Roger Cicala

    Derek, it seems a lot of people are interested. I can’t ever see us being the middle man, but I could certainly see offering a testing service.

  • Derek


    I’ve often thought that someone could make a business out of this. I want to be able to buy a new lens on B&H and have it shipped to someone (like you guys) where you’ll open it, run it through a gamut of tests and either:

    1. Certify that it’s fine and ship it to me.
    2. Make small adjustments then ship it to me.
    3. Declare it to be “bad” and send it back to B&H for a replacement where the process starts over

    I would certainly be willing to pay a few hundred dollars (per lens) for this service (that’s nothing when a lens costs $2k+.

    The piece of mind and lack of hassle would be awesome!

    What do you think??

  • Roger Cicala

    Flatlux, I think that is a true concern – right now we’re just another repair customer everywhere and I’m comfortable saying what we see is just like what you’ll see. If I make threats somebody might just quietly treat us differently knowing I’ll be blogging about how great they are. I’m sure the Lensrentals accountants would like that, but it’s not my goal.

  • fiatlux

    Roger, I think you should announce that, by the end of each year, you will publish stats on the quality of service centers (as you do for reliability). This should motivate them… or they just could reserve their premium service to your repairs…

  • Kari K.

    Years ago I had just the case described “in spec – you should focus in the centre part of the lens”. That comment came from the makers local service center. I had a 20 mm lens, that had the righmost 1/3 part of the frame off severely. – The right part of the lens was backfocusing so to say.

    At that time there was no handy available means to prove the lens to be faulty – no digital. So, later, in FF digital time, I spent several hours to tune the lens and adjust the manufactured tilt away. Eventually I had to adjust the reverse side of the lens mount mechanically. The result: the lens is now better – noticeably.

    I understand that this kind of tuning may not make profit to the service center. So it was “in spec”.

  • Kerry C

    Thanks, Roger. That makes me feel better about some of my expensive lenses and certainly explains why the supertelephoto lens I recently rented from you was spot on 🙂

  • Roger Cicala

    Kerry, there’s no clear correlation with price, really, especially when you consider that people are probably much more careful with an expensive lens. There are a few correlations, though:
    Supertelephoto prime lenses stand out for rarely needing adjustment.
    Wide angle zooms are the lenses most likely to need re-adjustment.
    Wide-aperture primes do, too, but that’s probably just a function of the shallow depth-of-field makes problems more apparent.

    But I’m sure you noticed – those are all fairly pricey groups of lenses.

  • Kerry C

    I’ve always assumed that testing lenses was a very scientific and …boolean… process. You’ve definitely educated me that it’s much more analog and subjective. I’m appreciative.

    Do you notice any correlation between the retail price of a lens and how often it requires factory-level adjustment (excluding drops, of course)?

  • The bookshelf story is pure gold.
    Could you post one of those pictures? Pleeeeeeeaaseeeeeeee 🙂

    Also, you could just post a list of manufacturers that have done this to you at least once. It would be just like a list of all manufacturers out there, but it would be much more explicit than “yours is like that too”.

  • Roger Cicala

    Intrnst, I try to be fair and not fuel Fanboys. The truth is I’ve had this happen with almost every company more than a couple of times, so I can see no purpose in naming names.


  • Steve

    Excellent write up Roger!

    I have had my own encounter on several occasions trying to correct some decentering issues with Canon… Three lenses, actually… A 24-70 II, 17-40 and 70-200 II.

    With the 24-70 II, I gave them one try and they made no change to how bad the right side of the frame was. I even sent with CLEAR examples of how bad the right side was to the left. Needless to say, repair was a failure. I exchanged it after and got another which was MUCH better.

    Next up was a 17-40… They tried once, no luck. Sent it back again and they replaced some optical elements which improved it SOME, but still was really bad at 40mm on the left side. Sent it in a third time (all on their dime) and still no change. I figured it was a lost cause.

    The 70-200 II was my latest… At 70mm, right side visually softer than the left. Two service center visits and almost no difference in IQ.

    I don’t deal well with decentered lenses, so I heavily check for that when I buy new lenses now. Any sign of it, it goes back to them. I wish service centers can get better at fixing this, especially when it is BAD.

  • intrnst

    Roger, I may be dumb or slow (ok, both isn’t off the case), but why not just start giving numbers and names — like you already did with lots of lenses and cameras. Considering your actual “badge” in the photo community, if you start telling who’s who, the service centers (and brands) will fell like treating you (and us) more “attentively”. Competition is the name of the game.

    Just sayin’…

    Thanks for the post.

  • A

    I suspect it could just be a lack of training that’s to blame.

    I’ve lost count of the technical jobs where I’ve heard the words “full training will be given” at the interview, or on the job spec; where the reality is usually that you spend the first ten minutes talking to a bloke called Dave whilst he’s working, and from then on you are expected to magically know everything. That’s despite having told them at interview you know absolutely nothing about the subject at hand!

    Even if they have the best test equipment in the world, and the best of intentions, people with no training aren’t always going to be able to achieve the best results.

    If you’re told that the big box with the lights in it makes the lens magically better. Or worse, the big box with the lights is very expensive, you’ll be fired if you break it…

  • Mike

    It is indeed very convenient to say “in spec” when these specs aren’t published anywhere.

  • KimH

    Thought about whether to write my first thought when reading another of you excellent articles.

    Here goes the thought:

    Some manufacturers must think that you’re a bit like a “Fart in a SpaceSuit”. There’s no way to get that visor up 🙂

    I completely agree with your suggestion. “the (first) one to address some of your suggestions will win customers over” – quickly. The high margin customers, many of who are regular readers of your blog, would be more than ready to add a bit more to their price or price of repair to KNOW that they got the best possible out of their product/purchase.

    Thanks again for a very insightful article!

  • Roger, I’m glad (sort of) that the “in spec” frustration I had with a lens wasn’t unique. It was badly decentered and I had sent them good photos to demonstrate. My lens came back with some lovely cleaning marks from them at no charge.

    The moral of that story for me is to now rigorously test any new lens within the store’s refund/exchange time limit.

  • Roger Cicala

    Kyle, we don’t have to adjust that one often at all. But the front element rotates on a ramp for 105 infinity focus, and the rear element can be adjusted.

  • KyleSTL

    If you have any information on the Canon 24-105 f4 I would love to know what you have found out about adjustments. I replaced apertures in two copies myself (mostly due to the increased courage caused by reading your blog posts), and I would happily tinker with it myself to try to improve it (especially since reading this post and my odds of being ‘in-spec’). I’m an engineer, that’s how we roll. Any information you have on it would be greatly appreciated. Thanks again for the best camera blog on the web.

  • Roger Cicala

    Kyle, right now we can’t even consider it. We’re already overworked here, just doing our own stuff. Even if we weren’t, there are only certain lenses we’ve figured out how to adjust: remember the factory keeps this stuff secret so we have to reverse engineer it by trial and error. Every lens is different, and there are only a few dozen we know how to do.

    I’m not too upset when I mess up one of our lenses. But it would be an entirely different thing to mess up someone else’s.

  • KyleSTL

    Great writeup, Roger. My question is, when will you open up your services for these adjustments for hire? How much would you suspect your typical lens would cost to perform such a service? I have a couple of lenses long out of warranty I have been meaning to send to the manufacturer to adjust optically after aperture replacement, and I’d trust you and your team just as much (if not more) than the factory.

  • Chris

    Great post Roger. I am dealing with this exact problem, and I appreciate your level of detail, and gumption to jump in and do it yourself.

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