Variation Facts and Fallacies

Lens sharpness is widely discussed on the internet, so it shouldn’t come as any surprise that lens softness is also a major topic. However, my experience both as a photographer and as the owner of a lens rental business has shown me that much of this discussion is based on a fallacy. So just what is it reasonable to expect from a lens and how doggedly should you pursue the ‘best copy?’

Fallacy:

  • Noun - "an error in reasoning resulting in a misconception or presumption"

A bit of background

When I started in photography most of the forums I learned from had at least one thread a day about someone’s 'soft lens.' They knew the lens was soft because their camera worked 'fine' with all their other lenses. After a few years of running a rental business, though, I found myself in the following situation three or four times a week:

'The lens you sent me front-focuses, it's not good.'
'OK, we’ll overnight you a replacement.'

Only to find, when the first lens came back, that all our tests suggested it was perfectly fine. And the customer is very happy with the replacement lens - apparently, this one is 'fine.'

So what causes this problem? It's rather simple, actually. The fallacy here is the definition of 'fine.' Most people assume that 'fine' means, 'perfectly calibrated.' It became apparent to me that cameras and lenses are not perfectly calibrated, but rather, they all have some variation. That realisation shouldn’t have been shocking; every manufactured product has variation, why should cameras and lenses be any different?

For the next several years I continued to investigate this issue, writing articles about it as I went. Reading all of them now is an overly-long exercise and I’ve learned a lot since I began writing on this subject. So it seems time to put a summary article together.

Manufacturing variation affects all lenses from all brands – the only difference is the tolerance levels considered acceptable.

Some Semantics

In most online discussions, things derail when different people understand the same terminology differently. Discussions of lens quality are particularly prone to that, so let me define the terms as I intend to use them.

A soft or bad copy is a copy of lens X that clearly does not perform as well as other copies of lens X.  There are bad lenses out there. They happen.  

A design choice affects all the copies of Lens X. Every lens has some design choices made that we may not like.

Copy/sample variation is a slight difference that can be detected between different copies of lens X, or different copies of Camera B. Copy variation is detectable, but usually not significant (compared to a bad copy which is always significant).

The Search for the Holy Lens Grail

Before we go further, there are some people that should probably stop reading here. If you ever think 'for $1,500 I demand perfection,' this is not the article for you, it will just get you upset. The laws of physics are not suspended, nor are techniques of manufacturing altered, just because you demand it be so. If you enjoy The Quest for the Perfect Lens and other fantasy games, just move along and save yourself the aggravation of being administered this particular dose of reality.

Why Variation is Inevitable

First, I should mention that the problem has received more attention in recent years, oddly enough, because our equipment has improved so much. A 6MP crop-sensor camera didn’t expose the flaws in a lens that now, a 24MP full-frame camera makes painfully obvious. Better lenses contribute too: when a lens had four really soft corners it was hard to tell if one side was worse than the other. On a newer lens with sharp corners the difference may be instantly obvious.

It’s probably not a coincidence that photographer and blogger Lloyd Chambers brought attention to the fact that camera mounts aren’t always perfectly parallel to the sensor when he was testing Zeiss ZF 21mm lenses on a 24MP Nikon D3x. There's every chance it would not have been apparent if he had been shooting a lesser lens on a lesser camera.

The key thing to realize is that the problem is not limited to one brand, one type of lens, or even just SLR gear. Landscape photographer Joseph Holmes found significant variation in medium format lenses and focusing. Testing website SLR Gear found a batch of 50mm lenses that were all softer on the right side than the left. At Lensrentals we found a group of 300mm f/4 lenses from the same serial number run almost all suffered electrical failures. Why is this so?

Manufacturing Tolerances

Manufacturing tolerances are just that: a range of acceptable values, not an exact point. In other words, what is specified as a 1/4 inch diameter screw may be anything between 0.247 inches and 0.253 inches in diameter (see this chart from an internationally-renowned industrial fastener manufacturer). The machines that make them can’t be more accurate than that at reasonable cost.

Did you know that every time a glass manufacturer makes a run of a given optical glass, the refraction index and dispersion vary a tiny bit? The glass manufacturer furnishes a melt sheet to the lens manufacturer so they can make tiny adjustments in thickness or curvature of that element to compensate for the differences.

The glass is probably a tiny source of variation compared to the other components that make up a lens or camera. In addition to the multiple glass elements, there are clips, shims, and grips that hold them in place within the lens. There are helicoids, barrels, gears, and rings move them around to focus. Electrical motors and circuit boards tell them what to do, and, as Chambers has shown us, even the lens mount that connects the lens to the camera is a source of variation. 

Cross-section of a Zeiss 21mm lens. Note all of the clips, shims, and barrels holding the elements in position.

Many, if not most, of those components are outsourced to other companies or factories. A change in subcontractor could result in a slightly different part being supplied. Something as simple as a set of ribbon cables more likely to crack or a solder that is slightly less conductive being used on a circuit board could result in significant changes to a camera or lens.

If you delve into the manufacturer’s parts lists (when you can get them) you’ll find they take these variations into account and plan for them within a given tolerance range. For example, if you need to replace the front element of your Nikon 14-24mm lens (part # 1K104-xxx) you need to replace the adjustment washer behind it with one of five specific thicknesses - each copy of the lens requires a slightly different thickness for proper spacing of the front element to focus sharply.

There are numerous other variable-sized spacers and parts for every lens (most lenses have variable thickness spacers in at least three different places). In many lenses even the lens mount comes in several thicknesses or with shims so that the image focuses properly on the sensor. As someone who has to shim lenses fairly frequently, I can assure you it can be done close to perfection, but not perfectly. When a 0.06mm shim is indicated, we often have the choice of 0.05mm or 0.07mm shims - close, but not perfect.

Similarly, the lens must be electronically calibrated. The circuit boards inside each lens with its own AF motor contain adjustment screws to calibrate the frequency and current of the electronic pulses sent to the motor used to move the lens during focusing. Manufacturers don’t build in this adjustment because every lens is exactly the same; they build it in because every lens is slightly different and adjustments are necessary. And by the way: the factory manual gives an acceptable range for the adjustment, something like 150 +/- 2 KHz.

Frequency and voltage adjustment variable resistors on the printed circuit board inside a Canon EF lens.

It’s not my purpose to list every source of variation in a given copy of a lens or camera body. They are far too numerous. But just to give an idea of some major ones:

  • A lens has eight to 23 elements, each of which may vary slightly in its spacing from the other elements, centering along the axis of the lens, and tilting from right angles to the axis of the lens.
  • The focusing and zooming elements must move certain distances front to back within the lens and during their travel their tilt or centering may vary slightly.
  • The barrels and helicoids, and various slots in them, must machined so that the elements are not only aligned properly within them, but they are aligned properly with other barrels.
  • The lens mount may not be perfectly parallel to the camera’s sensor.

For everything on the list there is a slight variation within an allowable tolerance. You can demonstrate this for yourself if you have some friends (or camera club members) and can get several copies of the same lens. Mount a camera to a tripod and focus on a target that is very visible in live view at 10X magnification. Then, just change from one lens to another and watch the target be a bit off center in different directions with each lens. Just a bit for most lenses, but you might find one that's off target by half of the screen or so. 

Camera bodies are no different than lenses with regard to variation, and in fact could be even more problematic. Is the sensor perfectly parallel to the lens mount? Is the AF sensor properly calibrated to the imaging sensor? Is the AF mirror exactly aligned and angled in relation to the AF sensor? The list goes on and on. And in every case the camera is made nearly perfect, but not exactly perfect.

Lens-Camera Matching

During, and at the end of, the assembly process, the lenses and cameras are tested to make sure they are within the manufacturer’s specifications. If they are out-of-spec and get by quality control, then someone, somewhere gets a truly bad camera or lens. It doesn’t happen frequently, but it happens. When it does, it isn't a subtle call; it's very obvious the lens is bad. In mass-produced elements, quality control is likely to be conducted on a 'sample' basis - only one in every ten or every hundred units will be checked.

But even the cameras and lenses that meet specifications are still going to vary slightly. Many people think, 'I’ll try eight lenses and take the best one.' The reality though is that the only sensible definition of 'best' is 'best with the camera body you are using,'. This is because there is plenty of room for variance in the behavior of bodies, too.

Let’s consider just the lens mount as a theoretical example. First, we say the lens mount of a camera must be parallel to the sensor with a range of +/ - 0.05 degrees (I have no idea what an acceptable range is, I only know that they cannot consistently be made perfectly parallel). Then, let’s say camera A's lens mount has a tilt of 0.04 degrees to the right. Lens #32 has a tilt of 0.04 degrees to the left. The two tilts would cancel each other out, all would be magical, and the owner would write sonnets on the various forums praising his lens.

But let's say he sells his lens to someone whose camera's lens mount has a tilt of 0.03 degrees to the left. The lens and camera now both tilt to the left and the new owner may say, 'the lens you sold me is a bad copy, it’s horribly soft on the sides.'

And this is just tilt. The mounts may also vary in thickness. There is variation, too, in autofocus systems. Certainly more than there is in lens mounts. Through-the-viewfinder manual focus will also vary (you might be surprised to know that viewfinder focusing screens are shimmed by hand). Even exposure metering varies slightly from camera to camera, and requires recalibration if it’s out of specification.

The bottom line is every lens varies slightly, in several respects. And every camera varies slightly too, in a number of different ways. A given lens on four different cameras will behave slightly differently on each of them, and four different copies of the same lens will each perform slightly differently on a given camera body. How differently? Well the short version is you probably will notice the differences if you’re a 'pixel-peeper'. If you use cameras and lenses to take pictures, though, it would be very unlikely you’d notice normal variation, even with large prints. The one exception might be high quality wide aperture lenses because the narrow depth of field may make subtle differences apparent.

So how much of a difference does this make? Click here to read page 2

The views and opinions expressed in this article are those of the author and do not necessarily reflect the views and opinions held by dpreview.com or any affiliated companies.

Comments

Total comments: 231
123
LightRoom
By LightRoom (Nov 26, 2011)

So let's see. We are paying a lot of money for a quality lens. But then for X Y Z excuses we are going to get an inferior lens? EXCUSE ME! What a load of bull! So typical of nowadays! If you are charging a wonderful price for a wonderful lens, I expect your lens to be wonderful.

But no, we should pay for full quality, when manufacturers to save costs move over to cheaper countries with cheaper workforce and lower quality checks, leaving a lot of people unemployed.

But we should understand? Well no, sorry. F U . Not only we don't understand, we don't want to. And we will not.

If a product is sold saying it ill meet certain standards it should. The rest is a load of lame excuses, and if you ask me, a fraud.

Have a nice day!

1 upvote
Antony John
By Antony John (Nov 26, 2011)

Think you missed the point of the article. there are engineering tolerances that have to be taken into account. For want of a better word it's called 'physics'.
Guess you never take a bad photograph, it's always your equipment right?

3 upvotes
jhinkey
By jhinkey (Nov 26, 2011)

Yes there are tolerances, but tighter tolerances cost more - more to manufacture, more to inspect, etc. Each company makes decisions on what tolerances are good enough - it's statistical-based analysis. Sometimes the tolerances of lens and camera add up in a bad way. If they do there is nothing keeping the purchaser from sending it in under warranty or sending it in for adjustment on their own dime. Unfortunate, but true.

LightRoom says he pays good $$ for his equipment, but how much more would he be willing to pay to get a 100% perfect lens and body? 2x, 3x, 4x more?

I've had no problems with sending lenses in to Nikon with proven problems and getting them to fix it (however if you just say it's not functioning well w/o any photographic proof they typically won't do much).

It's the same way with cars or any other item composed of many high precisions parts - sometimes you get a bad one.

Comment edited 53 seconds after posting
1 upvote
Antony John
By Antony John (Nov 26, 2011)

Then of course their are variations in tolerance due to thermal coefficients of expansion differences between components which will cause variations in the dimensions of parts at different temperatures.
So we need a lens mated to a camera body at constant temperature - who's in line to buy a bridge camera with close tolerance temperature control weighing 2 tons at $100,000?

1 upvote
Sosua
By Sosua (Nov 26, 2011)

Lol, Lightroom - I'm pretty sure you won't be a good enough photographer to notice these minute differences in the real world.

Read it again...

0 upvotes
Nigel Wilkins
By Nigel Wilkins (Nov 26, 2011)

@ Lightroom, You're not getting an inferior lens, you're getting a lens/camera combination built within what the manufacturer deems acceptable limits. These limits have to exist as perfection doesn't exist anywhere. They even managed to get the Hubble telescope out of spec the first time, which I'm sure cost a bit more than your camera lenses. When they fixed it, they only returned it to within "acceptable limits".
You say you want "full quality", what's your definition of full quality? perfection?
"If a product is sold saying it ill meet certain standards it should" - nobody's saying they don't meet certain standards, in fact, that's the exact opposite of what Roger is saying, most lenses do meet these standards. Some my not, but that's life (or statistics). Nothing & nobody is perfect.
BTW, I've done 100% quality control checks in manufacturing myself & can confirm that out of spec parts still get through.

0 upvotes
Ivanaker
By Ivanaker (Nov 26, 2011)

The more complicated to make the lens is, for example 14-24 2.8, or 70-200 2.8 (big $$$ lenses) there is a bigger chance that some of those 500 mechanical and optical parts inside is not perfect.
That`s why I shoot 50 1.8, the most simple lens to make, the cheapest lens to make, and probably the most performing lens there is.

0 upvotes
Dan Ortego
By Dan Ortego (Nov 26, 2011)

Thanks Roger,
I've owned Leica primes of the Lux-50, 28-Cron and Elmer-21. They were all fantastic! So much so that I've been terrified that I may never ever be satisfied with anything else. Well, I decided to give Sony and Zeiss a try, and the first lens arrives next week (Distagon 24/f2.0). I'm so glad to read this article because I was already planning to return it because its a 'bad copy'. Clairvoyance is bliss...

Comment edited 17 seconds after posting
0 upvotes
IEBA1
By IEBA1 (Nov 26, 2011)

I'd love one of those Zeiss cinema primes for the 5D thrown into the mix here.
http://blog.ieba.com/wp-content/uploads/2011/01/Picture-2.png

I mean, it makes no sense to me to have good glass (even a non-L canon lens intermixed with the quality of L and Zeiss lenses) that clearly has a very high resolution somehow be "not good enough" for video where there's line skipping, moire, and aliasing. If anything vDSLR users need to be adding softness, not sharpness. But every vDSLR user I talk to who is series about video completely shuns the still camera glass as totally inferior and goes after the cinema primes. I'd love to see them on the chart compared at full still image resolution to see what they truly offer.

1 upvote
cdidd
By cdidd (Nov 26, 2011)

Wow you're so clueless. Cinema lenses have cinema bokeh i.e. smooth mostly achromatic bokeh. And linear many bladed aperture. Also no dslr lenses exist with 12mm focal length and T1.3. and other things like better flare protection, better mechanics for manual focusing, color matching for a set, precise focusing distance markings, no focus breathing , T2 zooms with crazy range and nice bokeh etc etc

Just compare bokeh of zeiss master primes, espessially on oof highlights and any wide angle dslr lens. Dslr lenses are inferior in that aspect.

Comment edited 2 times, last edit 9 minutes after posting
0 upvotes
jamesm007
By jamesm007 (Nov 26, 2011)

Amazing the negative talk.

But people just don't like it because it means their camera/lens is not perfect. Well it gets worse. Over time your gear will drift out of alignment! All dSLR/lens manuals tell you to have them checked now and then to correct this.

My experience is that even if your dSLR shows outstanding AF it may need tuning. Its all relative you can say. To the person, body and lens.
I will just say its lack of knowledge that have people criticize the truth. Even if you have 80 years of experience in photography... gear has changed. I respect years of experience in photography but not comments made with not much knowledge of digital, mechanics and materials. Its price prohibitive to build a perfect dSLR and lens. Film was much more tolerant than digital, much more! Digital sensors are extremely demanding and sensitive! They are great instruments to test variations flaws in lens! Remember its all on a powerful computer! That's sees every bit of the picture.

Comment edited 3 minutes after posting
0 upvotes
CKDexterHaven
By CKDexterHaven (Nov 26, 2011)

Wow. A lot of words.
I don't know what to make of this. It seems to assert that there ARE sample variations. But, that we shouldn't care about them.

1. I have long been aware that pro photographers (back in the day) would routinely buy 3-5 copies of the same lens, test them, and keep only the 'best' sample.
2. In my own, similar, efforts, i've had occasion/opportunity to do just that with three lenses. All three exhibited variations so significant i was able to assess them on the camera's LCD screen. These were all current, fast 50mm AF lenses.
3. I've had two absolute dogs. A wide angle lens for the Mamiya 6, and a Leica-M 50mm Summilux-ASPH. Both were WAY off spec in one way or another. I don't doubt many people who don't test their gear would have used these lenses without knowing that their inferior results could have been avoided.

It's sad that the term 'pixel-peeper' has become so popular. It's unfortunate that it's used in such a dismissive manner. TESTING is important.

1 upvote
Earguy
By Earguy (Nov 26, 2011)

As an always-trying-to-improve hobbyist, it actually puts my mind at ease that I almost assuredly don't have "bad copies" of my lenses or body. My poor shots are a result of my lacking skill and technique. It's just nice to know that my gear is not messing me up. I have the tools I need, now all I need to do is practice and learn.

Thanks for a well-written, well-researched article.

1 upvote
Ashley Pomeroy
By Ashley Pomeroy (Nov 25, 2011)

"Trying to find exactly the sharpest copy of the sharpest lens is a fool’s errand: you’ll be looking for something that doesn’t exist."

You know, the same lesson could be applied to life in general. We live in a chaotic universe, where perfection is unattainable, not even for an instant. Our distant ancestors crawled from disorder onto shifting sands, and we are imperfect people with broken minds, trying to shoot down shadows cast against a backdrop of night. Ships that pass in the day.

You can't be with the one you love; love the one you're with. This is not what God intended.

0 upvotes
Lan
By Lan (Nov 25, 2011)

Welcome to DPReview Roger!

I check your LR blog every day to see if you've posted anything; so it's good to see you here!

0 upvotes
CameraLabTester
By CameraLabTester (Nov 25, 2011)

Yes, there exists in this wide wonderful world, a certain species and class of photo enthusiasts who would scrutinized the amount of play on the zoom barrel, the looseness of the IS or VR switch, the tiniest of sounds deemed out of the ordinary from the AF motor or IS/VR element, the nostril hair on the filter, the scratched paint obscuring the all important f2.8 label from the zoom or f1.4 label from the prime, the lint deposit on the switches, the rubber smells, etc etc.

You must also cater to these customers, of course!
They rent those expensive lenses just to cuddle it! :)

2 upvotes
steven2874
By steven2874 (Nov 25, 2011)

Now if we could get you to compare a dozen or so Canon S100's...

1 upvote
SaltLakeGuy
By SaltLakeGuy (Nov 25, 2011)

That's all well and good, but I just have to say I can not heartily agree with all that's been said. I've been at the digital thing since the mid 90's having owned at least 2 pro DSLR's and 7 other semi pro bodies. I can't even how many L lenses and Nikkor's I've owned along the way. With that said, AFAIAC Canon has the WORST consistency in their lenses of any manufacturer I've yet used. I generally had to return most L's purchased AT LEAST once as they provided unacceptable corner sharpness or focus accuracy. Generally speaking after replacements arrived I was pleased with the performance. I personally had Pictureline pull 6 24-70 f2.8L lenses from their stock and showed their salesperson how poorly they performed wide open with excessive CA and he agreed sending them all back for replacement. I finally got a perfect one from B&H first time out. IT is NOT ME, it is without question the product. I'm happy to report only ONCE did I have to return a Nikkor as all the rest have been great

1 upvote
DPNick
By DPNick (Nov 25, 2011)

Looks like you read past the part where Roger suggests that people like you should not read past.

11 upvotes
cordellwillis
By cordellwillis (Nov 26, 2011)

It's not you.

LOL

2 upvotes
dodfr
By dodfr (Nov 26, 2011)

This is a major problem I noticed many years ago ! in fact I only use pocket sized digital cameras but as I had opportunities to make some bulk purchasing of same model for myself and friends that followed me on the choosed model, I used to test them all upon reception and I rarely got same result for each ! I always got some warmer or colder colors, soft corner lens sometimes up-right, sometimes bottom-left, sometimes more sharp at full tele than wide angle, some time the reverse.

It's economicaly more interesting for the manufacturer to wait for some customers the complain and send him replacement model that improving verification chain or manufacturing tolerance.

0 upvotes
taintedcamera
By taintedcamera (Nov 25, 2011)

As always Roger, great reading.

Your sites articles page sits alongside only the best inside of my Favorites Bar.
Now I need something to rent... :>)

0 upvotes
HowaboutRAW
By HowaboutRAW (Nov 25, 2011)

Great to read.

Does anyone here think that anyone from Sony or Sigma, two big sinners, will read this post and treat some of the points seriously?

Crickets chirp.

0 upvotes
Mike Sandman
By Mike Sandman (Nov 25, 2011)

Great article Roger - rational from start to finish.

dPreview, give us more articles at this level of technical detail.

0 upvotes
Jaims
By Jaims (Nov 25, 2011)

Great article, Roger.
I had already read some article along the lines of yours, but the way you explain and summarize it all is just great.

Many many thanks.

Best regards,
Jaime

0 upvotes
Desifinado
By Desifinado (Nov 25, 2011)

I learned a long time ago that certain lenses hit it off with certain cameras. Those lenses rarely leave those cameras.

0 upvotes
DioCanon
By DioCanon (Nov 25, 2011)

Very interesting article, I was a bit angry I have to take my Canon 60D and the 16-35mm L to calibrate.
But now I understand many things that I've never considered before.

Said that, I am still angry because I have 3 grands of Camera-lens that I have to take to service and wont be able to use it for 2 weeks (yes I know Canon call center says a couple of hours but when you walk in they say 1/2 weeks!).

Conclusion: ARE ALL LENS REVIEW USELESS THEN???
if results are so massive from lens to lens,
from camera body to camera body,
and from any combination of the 2?

Why being bothered to check a review be4 buying a lens? (thats for you DPR!)

1 upvote
MaikeruN
By MaikeruN (Nov 26, 2011)

Thats just the way it is.

0 upvotes
mlackey
By mlackey (Nov 26, 2011)

Outstanding!

0 upvotes
PicOne
By PicOne (Nov 25, 2011)

"If you ever think 'for $1,500 I demand perfection,' this is not the article for you, it will just get you upset. The laws of physics are not suspended, nor are techniques of manufacturing altered, just because you demand it be so."

Perhaps not... but for the more money spent, the more I would at least presume the QC procedures prevent crappola from actually hitting the retailer shelves. Your term "allowable tolerance" I would also presume is a floating definition. Again I would presume that more expensive lens productions lines have more stringent definitions of 'allowable' applied.

Indeed you seem to argue the opposite, in that the potential tolerances are much greater with lenses with more elements/groupings (ie. more expensive lenses) than lenses of simpler construction, and that therefore buyers should expect more expensive lenses to perform worse than cheaper lenses.

1 upvote
Philip Goh
By Philip Goh (Nov 25, 2011)

The more elements there are in a lens, the more complex it is. In a system that is more complex, there is a lot more that can go wrong.

3 upvotes
martian1
By martian1 (Nov 26, 2011)

Lenses with more elements/groupings do not necessarily perform worse than simpler lenses, even for the same allowable tolerance, as not every element/grouping exhibits the same sensitivity, i.e. a certain variation may cause different levels of image quality degradation depending on where in the construction it occurs.

In a good lens design the allowable tolerances are specifically defined for each construction element depending on the impact of variation on image quality.

Consequently, a well-designed lens on average performs better than a lesser lens, independent of the amount of lens elements/groupings.

0 upvotes
WJD
By WJD (Nov 26, 2011)

I made the switch from SLR to DSLR in 2003 having started with 35mm in 1972. I've been shooting digital via Canon exclusively starting with a rebel, then 30D and now two 40D's and 5D Mk 1. With EF, EF-S and L lenses I have not once thought I had a 'bad copy'. Every bit of softness in photos of varied types (landscape, portrait, macro) was proven to be operator error. This great article confirms what I've always suspected - bad copies are rare but less that great combo's occur and user error occurs even more. But that's just my opinion (I'm an engineer in a disipline far from optics)

0 upvotes
Martin Ocando
By Martin Ocando (Nov 25, 2011)

Real eye opener. So LiveView remains the most reliable focusing tool ever, and if you use a tool like Magic Lantern on Canon cameras, where you can zoom in 10x in LV to focus, is even better.
Feel better now not having MFA on my 60D.

Thanks!!!

0 upvotes
photo nuts
By photo nuts (Nov 26, 2011)

Errr... Actually even without Magic Lantern, one can still zoom in during LV for focusing on the 60D. :)

MFA is over-rated. It is practically useless for a zoom lens... at least in the current implementation on all Nikon and Canon cameras. Only some Oly cameras and the upcoming 1DX have variable MFA for two ends of a zoom lens.

1 upvote
Paul Farace
By Paul Farace (Nov 25, 2011)

I always thought depth of field and a relatively fast shutter speed would save my a$$ from bad lenses... looks like this confirms it.

Cameras today still beat what came before and why should we worry anyway? Afterall arn't the youngsters all trying to achieve the blurry box camera look with their HOLGA's and HOLGA-apps in post-production as well as lensbabies?

madness... oh the madness! :o)

5 upvotes
bronxbombers
By bronxbombers (Nov 25, 2011)

Good stuff, although I personally think you rther underplay how easy or not it is to notice differences. I didn't find it difficult at all to notice difference between various liveview AF or MF attempts and you show those to have been rather more minor than other differences you claim are hard to spot.
Maybe you lucked out with the liveview focusing though. I've found that unless you take at least six tries, and sometimes you even need more, the simple difference in focusing can completely alter results of how one lens appears to fair against another. In terms of details shown maybe it's not a lot, but the bite of the microcontrast, how fast thin dark details next to light can be pretty easily spotted.

0 upvotes
RCicala
By RCicala (Nov 25, 2011)

That's a very good point. For testing purposes though, I have all the time in the world to use Liveview from a tripod aiming at a star chart with great light. I wish I was half that accurate using it in the real world. So I think the liveview variation I showed here is probably a lot less than I have when I'm out doing real shooting.

Roger

0 upvotes
bartP
By bartP (Nov 28, 2011)

Yeah photography can be a hassle, taking all the fun out of it. In the film days printing only pretty small it was good fun. Now even with live view focussing is a hassle, since you focus perfectly wide open en shoot out of focus thanks to focus shift. The only way out is to find out how the lens performs with that shift at that distance at that f-stop and micro-adjust it. That was a great tip Roger! This new article has got me relax a bit and worry at the same time, but not too many worrries, everything under control if you take the time to prep things first, like a pro ha ha .

Comment edited 2 times, last edit 1 minute after posting
0 upvotes
makofoto
By makofoto (Nov 25, 2011)

In the movie industry we use $70,000 zoom lenses and $24,500 prime lenses, that are ostensibly made to a very high standard by companies like Zeiss and Leica. Before every job the camera assistants get a camera prep that is anywhere from one day to a month long depending if it's a relatively simple commercial or an epic feature film. Even though the quality of the lenses has gotten better over the 34 years that I've been in the Biz, we still have to have adjustments made to our Flange Depth and/or lenses during the Prep in order to get the lenses/cameras as close to perfect as possible. Note that in high end filming, the camera assistant usually keeps things in focus while NOT looking through the camera. He gets Focus Marks on the lens or Follow Focus by taking measurements and then gauges the subject matters relationship to focus marks and camera. The Camera Operator is the one looking through the camera during the shot.

... to be continued

3 upvotes
makofoto
By makofoto (Nov 25, 2011)

... We had a weird situation last week where a 16 mm Zeiss Master Prime, a T1.3, 4.8 LB beauty, with a front diameter of 114 mm, and a price tag in the $15K range. It focused short, ie. at a measured 4' it eye focused to 3' 9". All of our other lenses focused right on. When we put the that lens on a Lens Projector ... a projector that uses an etched metal resolution chart, it came up right on. Our other 10 lenses also came up correct on the projector. We had to use a different size shim in order for it to focus correctly with our $70K, Arri Alexa HD digital cameras ... but then it didn't focus correctly on the projector?! We had two technicians and two camera assistants checking each other. Weird stuff happens even with the most expensive gear!?

download the brochure for Zeiss Master Primes: http://www.arri.com/camera/lenses/35_format_lenses/master_primes.html#_blank

Snap shot from the shoot: http://images110.fotki.com/v109/photos/4/43793/4909192/Madeline2nd-vi.jpg

3 upvotes
makofoto
By makofoto (Nov 25, 2011)

btw. our renowned director said our lenses were too sharp and he would be softening the images from 7 days of filming! So yeah, spend more time capturing the moment instead of being a lens tech!

1 upvote
HowaboutRAW
By HowaboutRAW (Nov 25, 2011)

Gee and so much is out of focus in movies.

0 upvotes
Ashley Pomeroy
By Ashley Pomeroy (Nov 25, 2011)

"our renowned director said our lenses were too sharp and he would be softening the images from 7 days of filming!"

Did you strangle him? Did you consider strangling him?

1 upvote
IEBA1
By IEBA1 (Nov 26, 2011)

Better to start sharp than start soft!

0 upvotes
fus
By fus (Nov 25, 2011)

Great article. It has now come to be a painful truth to most pixel peepers but good to see it written for the non believers.

2 upvotes
Jule
By Jule (Nov 25, 2011)

Nice - really appreciate this articel.

Kind Regards

0 upvotes
Pangloss
By Pangloss (Nov 25, 2011)

Thanks Roger for another great article, summarizing your accumulated experience on the subject. I like your conclusion too!

0 upvotes
NFR
By NFR (Nov 25, 2011)

Excellent article! Every photographer should read this!

1 upvote
aleksdat
By aleksdat (Nov 25, 2011)

It' a TRUTH!:))

0 upvotes
CG33
By CG33 (Nov 25, 2011)

I agree, great article.

0 upvotes
WilbaW
By WilbaW (Nov 17, 2011)

Hello Roger. Great article. I have included a link to it in one of mine. You might be interested since we have some territory in common -
http://www.dpreview.com/articles/5402438893/busted-the-myth-of-open-loop-phase-detection-autofocus

1 upvote
berni29
By berni29 (Nov 26, 2011)

Hi

Thank you very much for taking the time to write this article. Informative and enjoyable to read. Well done.

Berni

0 upvotes
LincolnF
By LincolnF (Nov 26, 2011)

Thanks for the article. I'm sure Ansel Adams would have loved to have lenses as sharp as we now enjoy. I believe he overcame the limitations of his day thru craftsmanship: both in brawn (lugging such heavey equipment) and in brains (developing methods to get the picture he wanted out of the developer tray.)

I'd like to suggest a follow up article on how hand holding a shot affects lens sharpness. I'm betting that the variations induced will be greater than the manufacturing variations noted above.

0 upvotes
C. Kurt Holter
By C. Kurt Holter (Nov 27, 2011)

Many thanks for a really comprehensive and informative article!

0 upvotes
Lights
By Lights (Nov 28, 2011)

Great Article from the real world. An analogy would be, when I was younger I had two friends with identical new cars...in a drag race one would consistently beat the other. I read an article much the same in Hot Rod Magazine, that it's not any one tolerance that makes much of a difference, it's when something is very complex, and you add all the tolerance variations up. A very small fraction of an inch or centimeter multiplied, can make quite a difference... Anyway excellent article (I've always thought the pixel peepers - and to a degree lens and camera reviewers on the net, never took enough account of this all)
Thanks.

0 upvotes
Klimt z
By Klimt z (Nov 30, 2011)

When the lens tube on any lens is extended it has play in it. The 2 or 3 tubes on some p&s zooms flex from this looseness when extended. Yet the performance is acceptable. I assume the AF works with the result and so "compensates" for the misalignment? However this would seem to indicate that there is a fairly large tolerance for misalignment of this kind?

Comment edited 2 minutes after posting
0 upvotes
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