Variation Facts and Fallacies

What is normal variation?

When we at Lensrentals started using computerized analysis (we use the Imatest package) to assess the MTF of large numbers of lenses, it became obvious that there is sharpness variation among copies. The example below shows the groupings for several different 100mm lenses: six samples of the Carl Zeiss Makro-Planar T* 2/100, eight samples of the Canon EF 100mm f/2.8 Macro USM, and twenty-four samples of the Canon EF 100mm f/2.8L Macro IS USM.

This graph plots center sharpness against a sharpness figure for the whole lens (measured in line pairs per picture height for unsharpened RAW images)

Two things should be apparent from this chart. First, there clearly is variation between the different copies of each lens. On average the Canon 100mm f2.8 IS L lenses are the sharpest, but some copies are sharper than others. And some copies of the other two lenses are sharper again. You can see how this might lead two different reviewers to hold slightly different opinions on which 100mm macro lens is the best.

Second, a true 'bad lens' is truly an outlier, and you can see a bad one way down on the lower left. The difference between a soft or bad copy and the main group is very large. The copy-to-copy variation that occurs between the other lenses is really minor. If you want to know how bad that bad copy is: our techs could identify it looking at JPEGs at 50% on a computer screen, but they'd be unlikely to spot it by looking at a web-sized image.

A second point about copy-to-copy variation must be made: the data above were for all of those lenses on one single camera body. As I've already explained, when you change the body the results change - the overall pattern will look the same, but each lens result will be slightly different. The sharpest lens on test camera A may well not be the sharpest on test camera B.

The example below shows two things. The green triangles represent multiple different samples of a lens shot on the same camera (notice that the range on both axis has been changed to illustrate the difference more clearly). We then took one of those lenses (circled) and shot it on 11 other camera bodies - the performance is represented here by the blue and red squares. As you can see, there is significant variation in the results from the different cameras.

A single lens (circled) was re-tested on eleven camera bodies (red boxes and blue diamonds)
from two different serial number series. All were brand new from box.

As suggested by our name, Lensrentals is a lens rental house, and as such I'd like to clarify one point: the variations that Ive been talking about don't occur because we're looking at used lenses. When we first started testing lenses, we made sure to carefully compare brand new lenses with our stock lenses to make sure that our quality assurance was keeping the stock lenses in good shape.

We buy new lenses in significant quantities; so we usually start testing a given lens by examining a dozen new copies right out of the box, then we start testing our rental copies. The graph below compares a group of new-out-of-the-box lenses with a group from rental stock to give an example. But in the graph immediately above, all of the camera bodies were new stock. 

We’ve only found one lens so far that did show a difference with age, but results from that aren’t used in any of these illustrations (I have discussed this in detail in this article).

 Focusing Variation

To give some idea of how small the difference between various lenses really is, we can examine the variation of a single camera's autofocus with a single lens. It's reasonable to assume that you shoot dozens of images with your camera and depend on autofocus to be accurate. You never notice, unless you look very carefully, that if you automatically focus on the same shot several times the camera focuses slightly differently each time. That’s why for testing purposes the data points I’ve shown were obtained using the best possible live-view manual focus for each lens.

But let’s look at the graph below, which consists of multiple autofocus shots made with one lens on one camera. First, I let the camera autofocus the lens once, turned off autofocus, and took 4 consecutive shots, represented by the blue diamonds in the graph. In theory they should be identical, since nothing was changed. In reality, they are just a little different, which demonstrates the amount of shot-to-shot variation in the testing method - very little, in short.

Without changing anything, I then moved the focus ring to one extreme or the other, let the camera autofocus again, took a single shot, and repeated that process six times. Those six shots are the red boxes. You can see the camera autofocuses the shot a bit differently each time (and this is with center focus point on a star chart: a near ideal situation). Finally, I focused the lens using live-view magnified focusing four consecutive times (represented here by the green triangles).

A single lens shot repeatedly with no changes (blue), manually focused 4 separate
times (green), and autofocused 6 times (red).

The scale in this series is changed again to illustrate the point clearly. It should be obvious that the variation of the camera’s autofocus system on repeated shots with a single lens is about 1/3 as great as the variation between different lenses. Autofocus microadjustment to the camera would improve the average AF performance to be nearly as good as the live-view focusing but it wouldn’t change the shot-to-shot variation (it would shift the red cluster towards the green results but it would remain just as spread out).

So How Big is This Variation in Real Life?

That’s really the point of all this. The variation I’ve described is easy to detect using modern computerized optical analysis. And we’ve seen that the variation between a truly bad lens and the group of acceptable lenses is very large. But how big is the variation between the different acceptable copies?

The best answer I can give is probably that it might be detectable by pixel-peepers, but not working photographers, at least hardly ever. Lensrentals has six full-time pixel-peepers on our staff (the inspection technicians) who are armed with a large array of well-lit charts to analyze sharpness, aberration, back and front focus, you name it. They can pick out a bad lens fairly easily, but can’t tell the difference between the best and worst images in the groups above.

But there’s a more scientific way to look at things than 'our techs said so.' The Subjective Quality Factor (SQF) is a measurement developed by Ed Granger and K.N. Cupery in the 1970s for Kodak and used by Popular Photographer for their lens reviews. Basically, SQF uses a mathematical formula, taking the MTF data from the lens (which we get from these tests) to predict with good accuracy how sharp a print would be perceived at various sizes and distances.

I’m not going into detail about SQF (for a more thorough discussion, see Bob Atkins' excellent article or the references below). The important part is that several experts have shown an SQF difference of less than 5 for a reasonably sized print is basically not detectable by human vision.

It’s a simple matter to have the computer calculate the SQF from the data we’ve already obtained in our testing. We arbitrarily calculate it for 8 X 10 inch print size, but the SQF difference would be the same for any reasonably sized print.

The graph below is for the same lens that I used for the autofocus example above, plus I added several other copies of that lens tested on the same camera. Then I had the computer calculate the SQF data for the best and worst copies. 

SQF for 8 X 10 inch print taken from selected MTF points.

As you can see the variation in SQF is less than 5, meaning theoretically, you wouldn’t be able to detect the difference in a print. The difference is real and can be detected by Imatest, or by a careful pixel-peeper armed with a few test charts, a large monitor, and too much time on their hands. But it wouldn't be significant enough to make an obvious difference in a print.

So What’s the Point of All This?

The main points are fairly straightforward:

1) Every lens and every camera exhibits slight variations relative to its twins that are detectable, but rarely significant.

2) Variations that wouldn’t make the slightest difference in a print may seem quite different when the numbers are presented in a lens review. And, just because one copy of lens X is sharper than one copy of lens Y, doesn’t mean they all are, or that they all will be in your camera.

3) Occasionally, an acceptable lens mounted to an acceptable camera combine their variations in a way that makes them unacceptable together. The lens may be fine with a different camera, and the camera fine with a different copy of the lens. 

4) Really bad, soft, out-of-acceptable range lenses do occur. They are fairly rare though and easy to detect.

5) Camera autofocus is more variable and less accurate than you think.* 

* Before you go all Major League Fanboy about the superiority of your camera’s autofocus system: autofocus variation exists in every camera from every brand we’ve tested. Want to prove it? Put a wide aperture prime on your camera, mount it to a tripod, and focus on something in the middle distance. Now move the focus ring to infinity, let the camera autofocus and note exactly where it ends up on the distance scale. Now turn the focus ring to near focus, let the camera autofocus on the subject at middle distance, and note the number on the distance scale. They will be slightly different.

When you buy a lens, and assuming your camera allows you to, you should microfocus adjust it. If you do it properly, using a sensible focus distance, it really does make a difference. Then do some very basic tests to make sure it functions properly, and go take some pictures. If you like the pictures it makes, then keep it.

Oddly enough, the conclusion I’ve reached from several years of dedicated pixel-peeping and lens analysis is this: 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.

Roger Cicala, Lensrentals.com 


For more of Roger's thoughts on lens and camera variation - and much, much more, visit his blog

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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