….Sorry, as an opener if these words are senseless, but I’ve noticed that whenever I buy a new lens or receive one back from service the VR is always left switched on….Well I never use VR, but should I guess that turning it on actually holds the lens parts more securely in place for transport or un-use, or positions the elements correctly first up….ie: switch it off for shooting and on for un-use (in my old fashioned case :-) ….or is this another wrong guess and just a coincidence.
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Functionality of VR has to be tested. You also expect that thing to work if you need it one day. Not using it, but pay for it, is in my eyes as senseless as the opener (using your own words).
Since the VR needs energy to operate but the lens doesn't get any while in it's box, what should happen? The mechanic holding the VR lens element in place is kind of a claw which opens when powered to let the element move - that's my guess. And even with energy VR shuts down after a couple of seconds, if you're not longer push the release button halfway down or the AF-ON.
Quote:Functionality of VR has to be tested. You also expect that thing to work if you need it one day. Not using it, but pay for it, is in my eyes as senseless as the opener (using your own words).
Since the VR needs energy to operate but the lens doesn't get any while in it's box, what should happen? The mechanic holding the VR lens element in place is kind of a claw which opens when powered to let the element move - that's my guess. And even with energy VR shuts down after a couple of seconds, if you're not longer push the release button halfway down or the AF-ON.
1: ….yes….i do rather wish that a more compact and less expensive version of a lens (without VR/IS) was available with the VR version….but, see another topic about the state of the industry….probably one version is all that is possible (so for most people the VR version)
2: I was thinking that at rest, when the turn off/turn on happens, the lens elements might be positioned correctly…it was just a thought.
IS works pretty "simply." Some physical method controls the position of the IS unit - be it an EM field, actuators, etc. All brands have different patents (well, sigma stole OS from Nikon VR, so they mostly have all unique methods) that give them rights to do it differently.
When the IS unit is initialized, it centers the IS group. Then a gyro collects movement data for frequencies between some range (canon IS is about 0.5Hz to 20hz) and initializes the movement in the opposite direction.
Traditionally the section of the lens that has the largest "sectional focal length" (i.e does not focus or diverge light or does this to a minimum) has been selected to turn into an IS unit, as the beam of light traveling through the lens will move the least if that section is disturbed. Those sections are also usually fairly stable re: aberrations, so it make sense. Recently canon developed an afocal IS unit, so it may be dropped into any optical system that can accommodate its size.
The IS unit may rest centered, or not. Depends how it is held. Often in optics spring tension systems are used to hold things still, so it is possible the IS unit is suspended in a net of springs that hold it very close to centered, and then it can measure the EM field to find the exact center and will move there upon initialization.
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@SoLong there will always be people like you strongly believe in "the lens would be better without VR". Let's just say, no none of us can do a comparison between an existing and a non-existing lens. There also will always be people begging for VR even in wide angle zooms. And there will be people like me, happy with a VR-switch on longer lenses. If I switch it off, I hear and feel something like a clutch falling in place. The advantages of a steady finder are high enough to let go some phantom sharpness which nobody can prove to be real.
@Scythels I really don't care which Japanese company stole from another Japanese company as all of them did steal a lot of German manufacturers. If Sigma cuts a bit of Nikon's profits, I'm fine with as I'm benefitting of Sigma's improved OS. Let's talk again about VR vs OS once I get the 150-600 Sports to compare it with 300/4E PF once I have it back from repair because of malfunctioning VR. But so far my experiences are:
Sigma's OS works better in one lens I have than any other Nikon VR of three lenses. I can use longer shutter speeds and still get sharper results.
Sigma's way of 100% check with Foveon sensor based measuring devices also lead to better and sharper lenses than any Nikkor I have (and I have a couple of expensive ones) - at considerably lower prices.
Maybe it's time for Nikon to learn from a better company? Call it stealing if you need - a thieve only could copy it. Sigma improved it as it appears to me.
If you wish to get into pedantics, virtually all of optics was stolen from Carl Zeiss AG, as their scientists invented most of the math and techniqes for lens design. The difference here is that Sigma stole a specific implementation of a mechanism from Nikon. The set of possible double gauss, tessar, sonnar, etc, lens designs is infinite. The set of possible ways to precisely move an optical unit such that it stabilizes the image passing through the system is very, very finite.
Sigma's QC method is insufficient. The spacial resolution of the sensor is lower (and crucially, lower than many sensors these lenses will ultimately be placed in front of), it is not of sufficient size to see the worst manifestations of bad alignments (spherical aberration is relatively insensitive to alignment error while astigmatism and coma are very sensitive). They also do not only let lenses which are "100%" through QC. All manufactures have tolerances, at all stages of the manufacturing. The lens design itself is extensively toleranced so that the radii of curvature, aspheric coefficients, lens and airspace thicknesses, and refractive indexes of the glasses may vary somewhat. The nominal design is not the specification for pre-manufacturing.
Further than that, the assembly is toleranced so that small alignment errors are accounted for and lenses with small errors still pass QC.
For the past several weeks I have been testing nine prototypes of a single lens. This lens is approx. 6-8x higher resolution than the average (or even "good") ILC lens. So far five of the prototypes have been rebuilt more than once to attempt to get them to meet spec. Without testing the lens on an MTF bench, interferometer, or other optical metrology tool you cannot with sufficient confidence tell how close to the nominal design (and thus, how close to spec) a lens is.
One camera manufacture does lens QC by taking pictures of a bookshelf across the room. This is horribly insufficient. I do not know what most do, but I do know a very high end limited production company does their QC by actually coupling each and every lens to an interferometer. This is the best form of QC. Any method that involves sampling the lens spot with a sensor without prior enlargement of the spot is insufficient.
"Case example" - one copy of a Zeiss 135mm f/2 APO-Sonnar was dropped or otherwise damaged but was still fine. The lens normally has an MTF at 30lp/mm (a frequency of interest) of about 75%. This is well above what is necessary for current-gen FF . The dropped lens had an MTF of about 45% at 30lp/mm, 30% below the manufactured and tested average. Clearly the lens has an issue. Yet, the MTF is just under 50% at the "true nyquist" for most FF sensors, so it may look just slightly softer than your average copy.
This is the issue with camera-based QC.
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Maybe it's time for Nikon to learn from a better company?
What makes sigma a better company than Nikon? From my PoV they aren't better than Nikon at much of anything except cleverly cutting QC and marketing it as more strict QC and offering lower prices.
I have the Nikon AFS 70-300mm VRII which I bought faulty, firstly the AF was sticking and the VRII seems to work when it feels like it. I posted on the Nikon lens site on DPreview about the problem and someone replied with a link to a AF repair guide.
Briefly, I disassembled the lens and repaired the AF, this left the the VR system with the same fault which is basically that it doesn't work in standby mode, ie when you switch on the camera it tries to go into standby, but then clunks three times and the image drops about the same amount as the AF point, then if you try to focus the VR does nothing,
If you wait ten seconds it fires up and functions perfectly while half pressing the shutter button, you can take photos and as long as you half press the SB the VR continues to function, when you let go after two seconds it cluncks three times the image drops and you have to wait ten seconds before the VR will respond again to the SB.
Taking shots with the VR not working results in soft decentered type images.In stand by mode the OS elements float in a magnet field "aligned", and can be used on a tripod, When the camera is off the elements drop and as far as I can see nothing supports them other than their pivot stops.
I am thinking of downloading the Nikon repair manual and going in to see what I can find, my current guess is one of the standby coils is adrift.
OS lenses are considerably more fragile than non OS.. Nikon want 300 euros for VR repair, I payed 70 euros it works, I just have to think ten seconds in advance.
Airy Discuss,
I can't comment on QC methods in manufacturing apart from a customers point of view, I have had Sigmas, Tamrons, Pentaxs and now Nikons and two out of three have been decentered, my call is quality control rests with the customer, if you don't send it back it must be a good one!
There must be a veritable "carousel" of duff lenses flying around in post vans waiting to fall back on shelves or maybe, maybe, back to the manufacturer, some of these lenses must have done many trips till they fall into the hands of an inexperienced user or someone who hasn't had the time to check!
I've seen far fewer reports of Sigma problems since they pledged QC improvements.
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AiryDiscus, your post contains some pretty stupid sentences.
100% testing means "each lens is tested" - if you are such an experienced tester, you should know it doesn't mean "each lens is perfect". Others might test one lens per batch, Sigma is testing each. 100% failure free is an illusion, to each manufacturer. I don't know a single one performing on perfection level.
I'm pretty sure you never saw a Sigma testing unit based on Foveon sensor in action, so just stop babbling about. I'm also pretty sure, I never saw it in action, so I better also stop babbling about  But contrary to you, I use Foveon sensors and see what they do and see how they outresolve the Sony sensors.
What counts to me: each Sigma lens design since they started their global vision thing was great - at minimum, and usually better than that. Neither you nor I do know the numbers of lenses sent back. If you're not totally ignorant, a simple check of the usual test sites tells, you don't know much about those lenses - otherwise show some bad results concerning their current lens lineup.
Look at Nikon or Canon and at their prices. And each Sigma prime of the art lens beats their offering, not only in price but in superior quality, resolution and contrast. The last Nikkor I got is in the workshop because of a faulty VR - the one Sigma "copied". Well, keep on telling they copied. To me it appears, Sigma finished their work and makes their OS performing.
A company which keeps up manufacturing cameras although their reputation is only highly appreciated in small circles while the rest moos with the herd, although they are loosing money with their cameras and offering those kind of reasonable prices while the general tendency is "price it higher", this is a better company. In my eyes.
"One camera manufacture does lens QC by taking pictures of a bookshelf across the room. This is horribly insufficient." Well, that's easy to agree. And can be found on many pictures left on a SD card when you get back the body from service, throughout all manufacturers.
"but I do know a very high end limited production company does their QC by actually coupling each and every lens to an interferometer." Sure, you're shopping at those kind of companies, aren't you. I'm not. Actually they can check it with a crystal ball, I don't care, as long as the lens is helping me doing great pictures.
"This is the best form of QC. Any method that involves sampling the lens spot with a sensor without prior enlargement of the spot is insufficient." Well, as I said, you never saw their A1 unit. You're talking about stuff you don't know.
FWIW my username was Scythels until I changed it to something a bit friendlier =)
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I'm pretty sure you never saw a Sigma testing unit based on Foveon sensor in action
I study optics and specialize in metrology and lens design. In the research lab I work in one of my current roles is to design and develop testing methods for advanced optical systems. One project involves the intersection of aberration theory and freeform surfaces. Freeform surfaces may be thought of as "aspheres+." It will be 10-30 years before freeform surfaces see use in mass-market optics due to the assembly and fabrication difficulties, but they will provide the same "revolution" that aspheres began so many years ago. Unfortunately, because there is no symmetry they are remarkably sensitive to assembly and manufacturing errors and aligning involves monitoring the aberration field until the correct alignment is achieved. This requires access to information about what aberrations are present in the image, thus interferometry or MTF bench testing (which enlarges the spot from the lens 20x or more and then re-images it) are the only way to analyze the system.
The A1 unit is basically a variable-flange APS-C camera. From sigma:
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The lenses to be measured are hooked up to the image capture device, and the special charts are captured and analyzed using new, proprietary algorithms designed to work in conjunction with the high-resolution sensor.
tl;dr it's a modified camera and modified ISO 122333 chart, with a new, proprietary demosaicing algorithm. There is no patent protecting this machine, it is not a new, "novel" method of testing. It's the same as a PZ or other review website chart-based test.
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But contrary to you, I use Foveon sensors and see what they do and see how they outresolve the Sony sensors.
Why the vitriol JoJu? A great deal of what I do involves working with sensors with "even higher" higher (that doesn't actually say much) spacial resolution than the Foveon chips because they are B+W, high-density sensors. The client's lens I am working with is specced at 104lp/mm corrected nyquist frequency. Even the 5Ds is only about 61lp/mm. This is a common small format sony HAD chip. If you would pardon my french, it "outresolves" the shit out of anything in your average camera.
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What counts to me: each Sigma lens design since they started their global vision thing was great - at minimum, and usually better than that.
Quite a few are "meh."
18-200, 18-300, 17-70, 30/1.4, 24-105 to name a few. In my personal opinion they are all rather poor, as are most camera lenses from a lens designer's stand point. They all merely "meet spec," as we say - smaller format optics and research-grade optics are corrected to about a full order of magnitude smaller spot size.
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Neither you nor I do know the numbers of lenses sent back.
Well that's not explicitly true. I have "dud" numbers from the largest buyer of camera lenses in the US. They say that the # of bad sigma lenses has not significantly decreased since 2009 when they began logging data.
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The last Nikkor I got is in the workshop because of a faulty VR - the one Sigma "copied".
A sample size of 1 (or 2, 3, 4, 5, and so on) does not speak for the population.
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And can be found on many pictures left on a SD card when you get back the body from service, throughout all manufacturers.
As far as I am aware, there is only one manufacture that does this... and I have data from all the big players.
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Sure, you're shopping at those kind of companies, aren't you. I'm not. Actually they can check it with a crystal ball, I don't care, as long as the lens is helping me doing great pictures.
Nope, I don't have anywhere near the $4500 to drop on one of their lenses. I just have a friend who spent last summer doing QC for them. I also know that the particular lens I am thinking of is regarded as one of the very best SLR lenses available at the moment.
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Look, Scythels/AiryDiscus: Testing one lens in each aspect and at the border of physical possible measuring devices is one thing. Especially if you have all time of the world and not a couple of some thousand customers waiting for the long ago promised units. Testing on production level and being good enough (which is better than others, especially at the prices YOU are not able to make the design (of the whole lens, not only the glass pieces to put them on an optical bench) for nor to manufacturing them on high quality level at reasonable prices.
You're beating over and over the same bush of weak design, poor quality and mysterious phantom superb designs. Please explain, if you see every lens tester confirming Sigma's qualities as stupid idiot? Do you really think, all Sigma customers are brainless jerks who simply don't understand they're buying crap? Or list some of the lenses you consider as "meh"- that alone is arrogant, because you're not able to do better at this price! - from another manufacturer which is "wow", but not at the cost of 10× the price.
Years ago I had a friend who went to university, we shared the same hobby and he often used the university's testing equipment like interferometers and other stuff to prove something. He very often argued like you do, so I'm familiar with student attempts to get a serious reputation. But pulling exotic lens design against photo-industry stuff is just like comparing a bicycle with a rocket. One brings you to the moon and with another one I go shopping. There are not much shops on the moon, so I leave my rocket in the garage.
It's just, the game is not working this way. Talking a bit more humble is not exactly a crime. Realizing real world lens business is something else than lens testing on a university campus could help you at the end to dig deeper. If you want to discuss glas on a scientific base with people who always understand your explanations, there might be better forums for.
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