Based on the focusing of the 55 / 85 FE lenses (and the new tamron 70-180), I am inclined to think this is correct. But if there is information to the contrary I'd like to see it.
That article does not discuss stepping motors in any detail at all. It mainly discusses ring USM motors compared to linear motors and USM motors are not stepper motors they are piezo electric motors. This article does not comment on stepper motives other than to note their accuracy, so it definitely does not say linear motors are fast than stepper motors. What is said about linear motors in that article could mostly be said about stepper motors -- they are very precise, they are fast, you can use more than one motor, they are quiet. The big difference between linear motors and stepper motors is that linear motors move in a straight line and stepper motors rotate, but if you only know the type of motor and nothing else about their specs, you certainly can't say linear motors are faster.
Here is a good basic article about stepper motors:
Steve Spencer wrote:
That article does not discuss stepping motors in any detail at all. It mainly discusses ring USM motors compared to linear motors and USM motors are not stepper motors they are piezo electric motors. This article does not comment on stepper motives other than to note their accuracy, so it definitely does not say linear motors are fast than stepper motors. What is said about linear motors in that article could mostly be said about stepper motors -- they are very precise, they are fast, you can use more than one motor, they are quiet. The big difference between linear motors and stepper motors is that linear motors move in a straight line and stepper motors rotate, but if you only know the type of motor and nothing else about their specs, you certainly can't say linear motors are faster.
Here is a good basic article about stepper motors:
I've definitely heard linear motors are faster; usually that's in the context of telephotos because linear motors have more torque. But pretty much all of the fastest focusing lens' I know of (55 / 85 1.8 FE, 70-180 tamron, 135 gm) use linear motors, and the manufacturers tout them as being faster with more precise AFC tracking:
https://www.tamron.com/news/press_release/20200407.html ("The lens utilizes Tamron's newly developed VXD (Voice-coil eXtreme-torque Drive) linear motor focus mechanism that produces an autofocus drive that's quieter and quicker than ever before.")
Dec 07, 2020 at 03:34 PM
Steve Spencer Offline • • • • • • • Upload & Sell: On
goldb wrote:
I've definitely heard linear motors are faster; usually that's in the context of telephotos because linear motors have more torque. But pretty much all of the fastest focusing lens' I know of (55 / 85 1.8 FE, 70-180 tamron, 135 gm) use linear motors, and the manufacturers tout them as being faster with more precise AFC tracking:
https://www.tamron.com/news/press_release/20200407.html ("The lens utilizes Tamron's newly developed VXD (Voice-coil eXtreme-torque Drive) linear motor focus mechanism that produces an autofocus drive that's quieter and quicker than ever before.")
You have heard that linear motors are faster, but do you have a source? In both of those quotes you are not comparing linear motors to stepper motors, so they don't address the claim you have heard.
Both stepper motors and linear motor can have either high or low torque and can vary substantially. The question is not whether stepper motors or linear motors are faster, but the question is how fast is the particular stepper motor or linear motor in a given lens at moving the elements that need to be moved. I have seen exactly zero evidence that one type of motor is faster than the other type. Instead everything points to varying speeds of both types of motors such that their is substantial overlap in the speed fo the two types of motors and of course the amount of glass that each motor pushes around will affect the speednof nAF for a given lens as we'll.
goldb wrote:
I noticed these use stepping motors instead of the ultrasonic type motors for AF. Is there a general consensus that the stepping motors are slower?
Motors stepping or ultrasonic can be fast or slow depending on the implementation. For example, the Nikkor kit zoom 18-55 DX has many iterations. While the previous AF-S (Nikon SWM) is relatively slow, the current AF-P (stepper) is the fastest-focussing lens I own. It's stunning. It reaches focus before I can register the motion.
Steve Spencer wrote:
You have heard that linear motors are faster, but do you have a source? In both of those quotes you are not comparing linear motors to stepper motors, so they don't address the claim you have heard.
Both stepper motors and linear motor can have either high or low torque and can vary substantially. The question is not whether stepper motors or linear motors are faster, but the question is how fast is the particular stepper motor or linear motor in a given lens at moving the elements that need to be moved. I have seen exactly zero evidence that one type of motor is faster than the other type. Instead everything points to varying speeds of both types of motors such that their is substantial overlap in the speed fo the two types of motors and of course the amount of glass that each motor pushes around will affect the speednof nAF for a given lens as we'll....Show more →
I haven't seen a direct technical comparison of linear vs stepper - but I have seen several mentions of "new" linear focusing systems being faster than older systems / the fastest the manufacturer makes - which I believe those manufacturer quotes state ( https://www.tamron-usa.com/product/lenses/a056.html ("The highest levels of autofocus speed and precision in Tamron’s 70 year history").
I haven't seen any mention of new stepper motors being marketed as the "fastest" the manufacturer makes. Tamron, for example, uses the linear motor in its 70-180 and says its the fastest its ever made - but uses the stepper motor in its cheaper 70-300. That, plus anecdotal evidence from user reviews, makes me believe the linear focus systems may be superior for fast moving objects.
Obviously there can be substantial overlap. But when talking about "whats the fastest?" So far what I've seen is that the fastest of the fast all use linear motors.
Dec 07, 2020 at 04:56 PM
Steve Spencer Offline • • • • • • • Upload & Sell: On
goldb wrote:
I haven't seen a direct technical comparison of linear vs stepper - but I have seen several mentions of "new" linear focusing systems being faster than older systems / the fastest the manufacturer makes - which I believe those manufacturer quotes state ( https://www.tamron-usa.com/product/lenses/a056.html ("The highest levels of autofocus speed and precision in Tamron’s 70 year history").
I haven't seen any mention of new stepper motors being marketed as the "fastest" the manufacturer makes. Tamron, for example, uses the linear motor in its 70-180 and says its the fastest its ever made - but uses the stepper motor in its cheaper 70-300. That, plus anecdotal evidence from user reviews, makes me believe the linear focus systems may be superior for fast moving objects.
Obviously there can be substantial overlap. But when talking about "whats the fastest?" So far what I've seen is that the fastest of the fast all use linear motors.
I suspect you have just been looking at Sony lenses and what they say about linear motors. It isn't too hard to see claims of faster speed for stepper motors. For example Nikon says: "The stepping motor improves the autofocus speed of a lens in both phase-detect and contrast-detect autofocusing." Nikon has gone with all stepper motors for their new "S" professional mirrorless lenses and regularly claim the speed advances of these lenses. Here is what Canon said in EOS magazine when they brought out stepper motors, "A Stepping Motor is designed to be very quiet, making it ideal when the lens is used on an EOS camera to shoot movies, as the built-in microphone is less likely to pick up noise generated by the lens motor. It also responds faster and switches to a new subject or subject position more smoothly." Here is what Pentax says, "PLM is a very new technology for Pentax and was shown first in 2016 in the HD DA 55-300mm F4.5-6.3 ED PLM WR RE. This lens happens to focus more quickly than any other Pentax lens thanks to its lightweight design. Canon calls it STM and Nikon calls it AF-P."
So we see Nikon, Canon, and Pentax all claim their stepper motors to be very fast. Each company uses stepper motors in different ways, however. Nikon uses smaller motors but sometimes employs multiple motors to increase lens speed (as they do in the new 50 f/1.2S and the 70-200 f/2.8 S). Canon sometimes uses much larger stepper motors that can be very fast. Pentax typically only uses smaller stepper motors but with lenses with small focussing groups. Each of these approaches can lead to very fast focus with stepper motors. These motors are particularly useful for contrast detect AF in mirrorless systems as they can switch directions in focussing really quickly.
None of this is to say stepper motors are inherently better or worse than linear motors. Linear motors can also very in speed, size and power. Sony has at times use multiple linear motors, at times has used larger linear motors, and at times used small focussing groups to increase focussing speed. Linear motors are also very quiet (like stepper motors) and can shift directions very quickly--making them suitable for contrast detect AF.
Both linear motors and stepper motors are relatively new introductions as focussing motors for lenses driven without doubt by their quiet operations (really needed for video), their ability to change directions quickly, and their precision (these latter two abilities make them excellent for contrast detect AF. Both types of motors can also be very fast if the motor (or motors) are powerful enough and the focussing group is small enough.
I see nothing to support the claim that one type is inherently superior to the other.
Steve Spencer wrote:
I suspect you have just been looking at Sony lenses and what they say about linear motors. It isn't too hard to see claims of faster speed for stepper motors. For example Nikon says: "The stepping motor improves the autofocus speed of a lens in both phase-detect and contrast-detect autofocusing." Nikon has gone with all stepper motors for their new "S" professional mirrorless lenses and regularly claim the speed advances of these lenses. Here is what Canon said in EOS magazine when they brought out stepper motors, "A Stepping Motor is designed to be very quiet, making it ideal when the lens is used on an EOS camera to shoot movies, as the built-in microphone is less likely to pick up noise generated by the lens motor. It also responds faster and switches to a new subject or subject position more smoothly." Here is what Pentax says, "PLM is a very new technology for Pentax and was shown first in 2016 in the HD DA 55-300mm F4.5-6.3 ED PLM WR RE. This lens happens to focus more quickly than any other Pentax lens thanks to its lightweight design. Canon calls it STM and Nikon calls it AF-P."
So we see Nikon, Canon, and Pentax all claim their stepper motors to be very fast. Each company uses stepper motors in different ways, however. Nikon uses smaller motors but sometimes employs multiple motors to increase lens speed (as they do in the new 50 f/1.2S and the 70-200 f/2.8 S). Canon sometimes uses much larger stepper motors that can be very fast. Pentax typically only uses smaller stepper motors but with lenses with small focussing groups. Each of these approaches can lead to very fast focus with stepper motors. These motors are particularly useful for contrast detect AF in mirrorless systems as they can switch directions in focussing really quickly.
None of this is to say stepper motors are inherently better or worse than linear motors. Linear motors can also very in speed, size and power. Sony has at times use multiple linear motors, at times has used larger linear motors, and at times used small focussing groups to increase focussing speed. Linear motors are also very quiet (like stepper motors) and can shift directions very quickly--making them suitable for contrast detect AF.
Both linear motors and stepper motors are relatively new introductions as focussing motors for lenses driven without doubt by their quiet operations (really needed for video), their ability to change directions quickly, and their precision (these latter two abilities make them excellent for contrast detect AF. Both types of motors can also be very fast if the motor (or motors) are powerful enough and the focussing group is small enough.
I see nothing to support the claim that one type is inherently superior to the other....Show more →
Thanks. That is interesting. I have seen commentary that stepping motors are better (generally) for video work since linear motors have a tendency for abrupt focus pulls / focus breathing - which might explain the canon quote. In any event, it seems there isn't consensus that one is faster than the other. I'll be interested to see if this sigma can handle moving pets / children.
EarthQuake wrote:
Has Lenstip done a full review? All I could find was a first impressions article, and there didn't seem to be a LoCA test in it. Can you post a link?
Yep there is a section in the first impressions called "Auto focus and a few comments on image quality" where they show their standard LoCa test (which is am image of a standard focus target, showing green and magenta shift either side of the focus plane). But the full review is yet to come.
It's amazing how this thread has me shifting purchase decisions. At first, I did a pre-order for the new Sigma 35 f/2. Then, with all the talk about the IQ of the Sigma 45 f/2.8, I decided to cancel the 35 f/2 pre-order and purchase the 45 with the hope that the new Sony 35 f/1.4, when it is announced and available, will render a little closer to the Sigma 45. Go figure.
freaklikeme wrote:
The 65 appears to be flat-field with low distortion and fairly even performance across the frame from wide open. The bokeh's more inoffensive than beautiful, but that's a compromise I'd happily make for a great all-arounder.
They nailed my idea of a perfect lazy three-lens kit from a focal length perspective, but I'm not as sold on the 35 and 24. I'd have to try both to know, but, right now, my inclination would be to go with the ZA 35/2.8 and 24 GM.
Those are my 2 AF prime lenses (35 2.8 & 24 GM) and I'm not inclined to change either of them, in fact like you I'm considering adding the 65 as well. A fairly small AF kit that'll get the job done.
Arty73 wrote:
intro Sigma I series Germany with bokeh examples in the video, skip to 10:00 min, what do you think of these examples?
There were no samples wide open. Also most of images were shot at close distance where blur hides possible issues with the transition zone. Can't even evaluate axial CA wide open either and it's not surprising images look screaming sharp at f/4 and f/5.6 like in many samples he zoomed in...
