Pay Attention to the Man Behind the Curtain

Published August 4, 2016


Metro Goldwyn Mayer

Metro Goldwyn Mayer

A Reasonably Non-Geeky Guide to Lens Tests and Reviews

Hardly a day goes by that on some forum somewhere a nasty argument is going on about lens testing and reviewing. (Going forward, I’m going to use the abbreviation R/Ts for Reviewers and Testers.) As with all things on the internet, these discussions tend to gravitate quickly to absolute black-and-white with no gray. This one’s great; this one sucks.

I made a bit of fun about his in a recent post. The truth is that most sites have worthwhile information for you, but none gives you all the information you might want. I’ve spent most of my life in various types of scientific research, and I’m accustomed to evaluating information from an ‘is this valid’ standpoint, not just ‘what does it conclude’. And because I get to see behind the curtain of the photography industry I have a different perspective than most of you. So I thought I’d share how I look at tests and reviews.

For the Paranoid Among You

I see this speculated about online sometime so let’s talk about the Pink Elephant in the room. These things are obvious facts of life. They aren’t massively influential like some people think they are, but they are real to some degree.

R/Ts like be first. First reviews get the most hits. Plus it’s cool to be the first one with a new toy. I’m guilty of this myself sometimes.

Manufacturers reward R/Ts. It may be getting a prerelease copy to write that first review. Maybe an invitation to be a paid speaker at a convention. some free loaner gear, or photography trip or two. Rewards and may have some influence, but there are no huge checks that make R/Ts say whatever the company wants, though.

There are occasional threats, too. Outright ‘cease and desists’ occur, although rarely (yes, I’ve gotten a couple). More often there is a discussion about why the manufacturer disagrees with something an R/T said. Sometimes the manufacturer is right, too. They have been with me a couple of times.

Most R/Ts don’t care much about rewards or threats. The biggest R/T sites basically get the best treatment from all manufacturers. Other R/Ts buy everything retail and won’t accept a loaner or any other reward to make sure you know they aren’t being influenced. You can usually figure this out pretty quickly if you read more than the graphs from their reviews.

R/Ts want to be credible. If they aren’t credible you won’t go to their site (with a couple of exceptions).

R/Ts do what they do for a reason. They are getting something out of it whether it’s direct income from advertising, publicizing their expertise, or even just getting a tax break for wallowing in their hobby.

The vast majority of R/Ts try hard to be impartial, but we all have our influences and preconceptions. If their income depends on ‘click-through’ purchases there may be a subconscious tendency to praise things a bit much. If they make their revenue from Google ads, generating controversy and lots of visits may be important.

Every one of us makes mistakes. I have, lots of times. I’ve seen others do it lots of times. I, and a lot of R/Ts tell you when we find an error. Some others quietly change results when they figure it out. Some others don’t ever realize they’ve made a mistake, or refuse to admit it.

Reviewing and Testing are way more time-consuming than you realize. Carefully testing or reviewing a lens takes dedicated, expensive equipment and a week or more of full-time effort. When you say ‘just test more copies’ or ‘why does it take so long’ you’re basically asking someone to cut corners and be sloppy.

Persistance of Memory, Salvadore Dali

The Persistence of Memory, Salvadore Dali


So What Do I Look At?

Everything I can. But I ‘consider the source’ for every bit of that information, because there are lots of good, but different, perspectives out there. There is a lot of disinformation, too. But in general, there are several broad categories of R/Ts that I look at, each with a slightly different perspective.

Crowdsourced Information

In some ways, crowdsource is the best information you can get because it summarizes a lot of people’s experience. The trouble is it takes a while to appear. Early adopters don’t have very much of this resource to go on.

It’s also important to know the sources of crowdsourced information and take it all with a grain of salt. There is a nice-sized cottage industry that posts positive and negative product reviews online for a fee at places like Yelp or Amazon. Positive and negative forum posts can be purchased, too. I don’t know if it happens in photography forums, specifically, but I don’t rule out the possibility.

Source: Carna Botnet via Science, 2013.

Internet activity at some given moment in time. I wonder who that guy is in the middle of the Sahara. Source: Carna Botnet via Science, 2013.


There are three types of online information I consider.


One Guy Said Online

This is really good information if you know the guy. If you don’t know them, at least by reputation, it’s probably not worth the electrons it’s printed on.


Lots of People Said Online

Once dozens or even hundreds of photographers have rated and commented on a given lens the information should be better than ‘one guy’. There’s going to be some bias, of course, reviewer expertise varies, and occasional mass hysteria does occur. But crowdsourced opinion does give you a good idea of how satisfied people are with their purchase.

The trouble is it’s fairly worthless right around release time. Fanboys and trolls dominate these discussions, and people are very willing to comment about what they don’t know about. One thing I do recommend: most crowdsourced review sites let you sort the comments by date. If the lens has been out a while, start with the newest reviews first. Far too many ‘reviews’ are written well before the lens was actually released for sale or during the hysteria around release time.


Lots of People Showed You Online

This is the best; the gold standard. You can look at actual photographs taken with the equipment you’re interested in. There are still shortcomings, of course. Online jpgs tend to make lenses with a high contrast look better than those with high resolution, for example. Postprocessing and photographer skill levels vary. But looking at a lot of images can give you the best idea about what a lens can do and whether it’s for you. More importantly, you actually know the person had the lens they’re commenting about.

Of course, us early adopter types don’t have a lot of online images to browse through. And, personally, I tend to get bored after a fairly short time and don’t look at all that many images. I also find myself creating self-fulfilling evaluations. If I want the lens, then bad shots are obviously by bad photographers and good shots reflect how good the lens is. Or vice-versa.


A Photographer Reviewed Online

I consider this is much different than ‘someone showed you images online’. Reviewers do their thing professionally. They have a site where you can find out about them: what they shoot with, how they make their living, what else they do. This is important to know because all reviewers will have some preferences and each will have a slightly different shooting style. Most take identical images in every review so you can get some direct comparison between this lens and that one.

A photographer’s review gives you the most information about what it’s like to use the lens in question. Here is where your find out things like how a lens handles, how quickly it autofocuses, how it feels in the hand, and how it compares to similar lenses the reviewer has used in the past. You’re also more likely to find out about color casts, bokeh, light flare, and behavior on specific cameras.

I would never buy a lens without either trying it myself or reading a couple of reputable reviews. OK, I would because I’m an incurable early adopter, often to my detriment. But I shouldn’t.

Critical reading is very important here. Far too often we get a huge forum debate about what “Joe The Reviewer” said, but nobody in the debate knows anything about Joe the Reviewer; they just read the summary of his review. Or more often, they just read someone else’s post about the summary of his review. What kind of photographer is Joe? I don’t mean good or bad. Does Joe work mostly in-studio, or do landscapes, or street photography, or just review lenses? If you shoot a fast-aperture, wide-angle lens in clubs at night, Joe’s review using it mostly stopped down for landscapes may not be pertinent.

I had an early experience with this when the late Michael Reichman, whom I had the utmost respect for, wrote a very positive review of the Canon 70-300mm DO lens. I bought it on the basis of that review (really just the summary of that review) and HATED it. Before I hopped on my local forum and started saying Michael must have been bribed by the camera company, or I must have a bad copy, I actually looked at the review more carefully. Michael had used the lens for images of large shapes with strong contrast and blacked-out shadows, never shooting into the sun. He instinctively knew the limitations of the lens and made great pictures with it. I was using the lens in an entirely different way, one that brought out all of its flaws.


Editor’s Note
Upon reading this portion of Roger’s piece, I wanted to agree and interject my own opinions on the topic. As someone who has written for dozens of photography websites over the years, and written hundreds of articles, as an editor, I’ve always ensured that writers understood two things. First, the FTC requires that all reviews online that have been paid for by a company, are accompanied with ‘clear and conspicuous disclosures’. This means they’re required to state if they have been paid in any way for the product review. This can be as easy as stating “I received this new camera from ____ to test”, but it needs to be said somewhere to avoid a potential punishment up to $16,000. Secondly, I discuss credibility. Often, websites and other sources share credibility among all the writers and authors – less people read who the article is from than you might think. So it only takes one person to potentially ruin that credibility. While I can’t enforce their credibility, I do make sure that all gear for review comes from a third party (Often, companies I’ve worked for have dealings with B&H Photo or other large camera stores, where we can get 30 day loaners for gear reviews, without sacrificing impartial dealings by going through the manufacturer directly), and make sure they understand the stakes at hand.


That said, I’ve had companies in the past (I won’t name names), who have tried to directly bribe me with reviews by saying “We’ll send you this product to review, and if you like it…review it and keep it. If you don’t like it, just send it back”. This is absolutely bribery, and it absolutely happens. It’s important to know your reviewer, and not only trust their judgment, but their integrity as well. That said, the best way to develop an opinion on a piece of gear is to try it yourself.

Zach Sutton

Imatest Tests Online

There are many of these sites. All have very good intentions, and most give very good information. BUT, and this is a HUGE BUT, all Imatest labs differ. The Imatest program always gives scientific appearing numbers and very pretty graphs. But few Imatest R/Ts tell you the very important details about how they tested. How far aways was the chart? What was the type, size, and quality of the chart? (A small inkjet-printed chart ISO 12233 chart will give very different numbers with the same lens than a large, linotype-printed SFR Plus chart or backlit film transparency chart.), 2013, 2013


Even different lighting can give different results. Then we have to consider if the images were raw or JPG files, and where the tester considered the corner and sides to be. For example, the ‘corner’ measured on an ISO 12233 chart in Imatest is in a very different place than the corner measured using an SFR Plus chart.

You also don’t even know if the corner number in that pretty graph compared and average of 8 measurements (horizontal and vertical in each corner), or just one. Did that center measurement average horizontal and vertical, or just give the higher of the two? Or was it and average of 4 (all 4 sides of the center box)? Oh, and speaking of that, the difference between the vertical and horizontal lines is NOT a direct measurement of astigmatism and anyone who claims it is, well, don’t put a lot of emphasis on their review.




There are at least a dozen other variables in Imatest testing. Most labs are consistent within the lab, except for variations in the camera used (which also makes a huge difference over time). So comparing Lens X to Lens Y using Joe’s Imatest Lab is a valid comparison. Comparing Joe’s lab numbers for lens Y to Bill’s lab numbers for lens Y is not. But if both Joe and Bill all say Lens X is sharper than Lens Y in the center but softer in the corners, then it probably is. And if Steve says so too, it almost certainly is. If Dave says it’s not, well maybe his copy wasn’t as good, or maybe his testing methods are different.

So, as someone who tested literally thousands of lenses for several years using Imatest, I recommend you take all of these sites in as a gestalt and do a kind of mental meta-analysis of them. There’s good general data there, but splitting hairs and over-analyzing it will lead you to a lot of wrong conclusions.

DxO Analytics Tests

Here’s something you may not know. DxOMark is not the only place to find DxO Analytics data. So there is a good confirmation source for DxO’s data that I use constantly. SLRGear/Imaging Resource uses DxoAnalytics targets and software for their tests and presents them in a nice, easy-to-use format. The also are very transparent about the tests they use and the way they perform them, which gives me a high comfort level with their results.

In general, DxO Analytics is a computerized target analysis, like Imatest. There are a variety of targets for different tests, including dot targets and slant edge targets, among others.



This gives some different information than most Imatest reviews and it is presented in DxO’s proprietary ‘blur units’ rather than more standardized MTF or MTF 50 results. We all know DxOMark likes to compress everything down to a single, and in my opinion less than useless, number. (Well it has some use since we immediately know that someone who says “DxO rated it as 83.2, the best lens ever!!!!” is a fanboy who doesn’t understand testing at all. Resist the temptation to try to reason with unreasonable people.)

But if you dig deeper, there’s lots of good information: how the lens performs as you stop down, a nice look at the sharpness over the entire field, and other goodies. It’s often more in-depth information than what you get from most Imatest sites.

I use DxO to expand on data from Imatest testing sites. It may give a more complete picture, but not a more accurate picture. There are lots of Imatest sites and that dampens the ‘copy variation’ problem down a lot. There are only two DxO sites so when they test a bad copy, there’s not 6 others to compare it to.

As an aside, nobody, no matter how much testing equipment they have, can take a single copy of any lens and decide it’s a good or bad copy. They can rule out horrid decentering or tilt, or truly awful performance. But that’s about it. They may have the best copy out of 20, or the worst. Trust me on this. There’s a reason I will no longer publish ANY single lens performance data; because I’ve been burnt by publishing data when I only had a single copy and thought it was good.

Also please don’t compare my series of 10 and say they should do that, too. I publish very limited data on a larger number of lenses, but I don’t go into the depth and detail that an Imatest or DxO site does. Not even close. They probably spend as much time testing their one copy thoroughly as I do just doing MTF curves on 10 copies. Like I said at the beginning, we’re each showing you different things.

Lensrentals Optical Bench Tests

First, we don’t pretend to be, nor intend to become, a full R/T site. We complement them, not replace them. We’re doing somewhat experimental and geeky stuff for our own purposes and letting you guys look over our shoulder. The feedback we get helps us refine our methodology. But our results, while not a true lens test in the reviewer sense, do give you some very different data that I think is worthwhile. How is it different?


OlafOpticalTesting, 2016

OlafOpticalTesting, 2016


  1. There is no camera. This is good because it eliminates all of the variables of testing different lenses on different cameras. It’s bad, because many of you want to know how the lens is going to behave on your camera.
  2. It’s done at infinity. For most lenses this probably makes no difference. But for Macro lenses, designed to work close up, I’d put less emphasis on our infinity testing. For wide-angle lenses, I’d put more emphasis on our optical bench testing, since target analysis testing will be very close, sometimes at 4 or 6 feet, focusing distance.
  3. Because it’s experimental and evolving, we’ve refined techniques so some older results aren’t correct, sort of like older Imatest results done on a last generation camera aren’t the same as tests done on a new camera. For example, I just realized (after a subtle hint from Zeiss) that our 55mm Otus results were done before we started rigorously testing every lens with and without cover glass. It turns out the Otus is a better performer with glass in the path, as you can see below, so the data on our website has been incorrect for a year. We screw up sometimes. That’s what happens when you do new stuff.
  4. We only provide very limited testing. Basically at this point we give you wide-open MTF and variation data. And if you don’t like MTF graphs, well, other than ‘higher is better’ you don’t get much out of our data. If you speak MTF, then you get more information than you would out of Imatest or DxO graphs.
OlafOpticalTesting, 2016

OlafOpticalTesting, 2016


So when is our data important?

  1. It’s really the only data for copy-to-copy variation out there.
  2. It’s multiple copy data, so it tends to smooth out the sample variation issue. Thought of another way, while we present only one small type of test, we do it on as many copies as you’re likely to see from all the other R/T sites combined.

So I look at our data to see about sample variation, and to look at the MTF curves. That’s about it unless you’re into the more geeky part of testing. Now, because I’m into engineering quality I’d look at our teardowns, too, because there’s nowhere else to find that kind of information. But that’s not really testing. That’s just cool geeky stuff.

TL; DR Version

There’s a lot of information put out there. Most of it is reasonably accurate. Not one site or place is the ‘correct’ one. No single review is the ‘best’ one. It’s like real life. Each of them gives you some information that you can choose to use, or not use, when you make your decisions.

If you’re an intense early adopter, well, just go ahead and get the lens. There’s no sense making yourself crazy trying to justify why you want it, and there’s no way to know, absolutely know, if it’s right for you without using it yourself doing the kind of photography you do.

If you want to make a logical, rational decision about which lens you should get, and it’s not ‘right-around-release-time-insanity’ o’clock, then do some intelligent reading. Screen several Imatest and DxO Analytic sites and get a feel for what they think of the lens. Look at Lensrentals data and see about variation and if, perhaps, there may be some difference between close and infinity performance. (For example, if we find the lens is better than most, but all the Imatest sites say it isn’t, there’s a good chance the lens is better at infinity than it is close up.)

Then read some real-people reviews, looking at more recent ones first and discounting, as much as you can, the ones that came out right around release time when fanboys, trolls, and maybe worse were clogging up bandwidth. Finally, read a couple of professional photography reviews and get some more input on how the lens handles and behaves in various conditions, and look at some photo sites for images taken with the lens. Remember that online jpgs, unless they let you download 100% images, aren’t going to tell you a lot about how sharp the lens is (although it may expose some flaws). But they should give you an idea about color, flare, and bokeh at the very least.

Or, be a fanboy, find one site that says exactly what you want to hear, and go post on your favorite forum that you have found The Truth and all other sites are incompetent liars.

Roger Cicala

August, 2016



Author: Roger Cicala

I’m Roger and I am the founder of 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 Photo
  • David Bo Hansen Cartagena

    I don’t know the ISO but that quality is also more than possible with my old Sony alpha 900 and Sony 70-200 f/2.8

  • Jim A.

    I have a Zeiss 21mm and take it on every trip where there will be good landscape opportunities. I had a 17-40 with auto focus and almost never used it. I guess we all have our unique habits.

  • RL, we’ve actually discussed putting our MTF and variance graphs up on the website with each product. We think it’s a good idea but it will require a fair amount of time and programming and there always is a list of things the programmers need to do. But we’re really beginning to make progress on that list and I think someday we’ll have that done. Seriously, maybe 2017.

  • RLThomas

    Roger, once again you’ve demonstrated why so many people trust and respect Lens Rentals. It’s so refreshing to get an honest and forthright perspective on what is often a confusing and sometimes frustrating adventure. That said, I must admit I’m one of those fanboys you mentioned at the end of your post. Yep, I click on over to and what Roger says goes with me. It may not always be 100% the truth but I trust him to tell me when he’s offering his opinion as opposed to presenting facts and there is no better source of reliable multiple copy performance data on lenses. There is also no better source on how gear is built. Your tear down articles are wonderful! I would never dream of taking apart a $3,000 lens of my own but I love seeing you and Aaron do it. For me, it’s interesting to see what trade-offs manufacturers make in designing their gear.

    I know I can search through old blog posts and get this info on some lenses but I would love having that kind of data at my finger tips when browsing through lenses available to rent or purchase. I would gladly pay extra on my LensRental HD subscription for that ability… hint, hint.

  • Carleton Foxx

    Corruption in the photo/video equipment reviewing industry is at scandalous levels and disclosures do nothing to ameliorate it. Mr Sutton makes a good case and I agree that the laws are needed, but the current system all but ensures that just about every R/T is irredeemably biased.
    Humans are remarkably easy to corrupt. As every doctor now knows (or should) all it takes is just a free logo coffee cup or a few desk trinkets to get them to change their prescribing habits and referring practices, usually to the detriment of the patient.
    A big part of the problem is that the writers at most of the big America-based review sites ignore the ethical standards of groups like the Society of Professional Journalists which admonish them to “Refuse gifts, favors, fees, free travel, and special treatment.”
    So imagine what a lavish Sony- or Nikon- or Canon-sponsored trip to Tokyo or Hawaii or Manhattan does to short circuit critical faculties….not to mention Canon paying your company to produce videos about their products.
    That is whiy LensRentals is such an important resource and the only one we can turn to for unbiased advice.

  • DrJon

    So in summary review of the whole article – if you ever decide to photograph large shapes with strong contrast and blacked-out shadows you’ll want the best 70-300 DO ever made, and in my extensive testing my one is just that, so feel free to make me an offer!

    Disclosure: sample size = 1.
    More disclosure: last time I believe a salesman about lens sharpness.
    Finally: it’s actually very good at the short end and great for CA everywhere… oh, you wanted sharp and some reach… that’s just fan-boy nonsense…

  • Martti O Suomivuori

    Sorry to hear that about Michael Reichmann.

  • Martti O Suomivuori

    I fell in a lake with my 5DIII with the Tamron 24-70 lens attached.
    Contrary to what they say, there are no floating elements in that lens.
    The camera came back alive today. The Tamron is an ex-lens.

  • Lee, you are probably right on the Milvus, we’re redoing all the old tests now but that process will take some time. Brian at the TDP is traveling this month. I think it will be a while before he is able to change those.

  • Lee

    I think it’s probably reasonable that most results fall within the “passing grade” range. Lens design is with sophisticated software now, we have glassmaking pretty handled, they’re designing for high resolution sensors, and user expectations are higher than ever. On a scale where 0 was unusable and unacceptable while 10 is perfect, I don’t think any prototype that would score a 2 would make it into production today. And you can’t set the scale in relative terms (eg 0 being a kit 55-200 and 10 being a 28 Otus) because it would be a constantly moving scale and it would be too subjective (are we considering value? It’s hard to call the 28 Otus a good value).

  • Lee

    Great piece Roger, interesting stuff. I like that you’re up front about mistakes and improvements, that’s the way to be.

    FYI might want to make sure TDP knows about the Otus, seems they’re using the old chart still

  • Thanks Roger, very useful advice. I always find it funny these review websites that rank cameras or lenses within a ridiculously large range, such as [0,100]. The funny part is that all their scores, regardless of the camera or lens fall within the [80-95] sub-range (the “feel good range”). Such sites carry little credibility and sadly I find that most sites fall in this category. That being said, from a non-pixel peeping point of view, most gear today is quite good.
    On a different note and as you clearly stated in your article, lensrentals offers unique information in that you measure many copies. Given your experience, how would you rank the various manufacturers in terms of quality control? Or at least: what lenses are more likely prone to have defects vs others. Say, what is roughly the risk to get a bad copy of a lens for a given brand (or lens type if it’s easier): 10%, 20%, 50% ? I realize this might be difficult to ansswer, but this type of information would be very useful to many potential buyers. Thanks.

  • obican

    That’s apparently the faith of most Zeiss ZE/ZF lenses. They have stellar optics but only a few of them ever make it into the field due to practicality.

  • John, a lot of different terms are used for basically the same thing. The sensor stack is the thickness of glass layers in front of the camera sensor. We reproduce that for testing with ‘glass in the path’ of the light beam leaving the lens, which in-house we call the coverglass because, well, it covers the microscope that takes the MTF images.

  • John Seidel

    Every time I think I have a fairly good hold on terminology, something new (to me) comes along. What is ‘coverglass’? Does that mean a filter on the front? Which one? Do differing thickness matter?

  • Edna Bambrick

    The primary mistake is in not questioning questionable results. The secondary mistake is not manning up to it and having the integrity, accountability and transparency that Roger does. Cowboy up.

  • Brandon Dube

    Is it a mistake to measure something different? I measured the compact primes, compact zooms, and Angenieux Style zooms with no coverglass knowing the Alexa uses a monstrous 7mm coverglass.

  • Edna Bambrick

    It was easier for you to write all of that than to just admit “yeah I made a mistake”? Google ‘epistemological arrogance’ someday when you have the chance.

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