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Canon EF and RF Lenses – All Autofocus Motors

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Re: Canon EF and RF Lenses – All Autofocus Motors

#71

Post by flipthefrog »

hyperbovine wrote: post #16
michh wrote: post #12

I’ve recently been shooting film with an old EOS camera from the 90s I bought used and it was really nice being able to use the EOS lenses I bought for my DSLR in the 2000s and 2010s. It’s a dying standard now but it’s really impressive it lasted as long as it has, with significant technological innovation on both sides of the lens mount while retaining full compatibility. A brand new EOS EF lens still works with an…

I must be old -- I vividly remember the Nikon crowd crowing loudly online forums (fredmiranda.com I'm looking at you) about how Canon broke backwards compatibility when they moved from FD to EF. Whereas you could slap an F-mount lens from the 1950s on any Nikon DSLR ever made, no problemo. (Remarkably, this continues to be true!)

Except if you mount an old, so called pre AI lens, on certain Nikons, you will have to disassemble the camera to get it off. Many modern Nikons can't autofocus older AF lenses due to not having a motor. And many AF film SLRs couldnt meter with manual lenses. So far from perfect compatibility. Nikon F mount was introduced in 1959. The oldest mount used today is probably Leica M from 1954

Re: Canon EF and RF Lenses – All Autofocus Motors

#72

Post by nayuki »

Amazing website. If I didn't know better, I thought this content came from Canon itself. A couple of comments from me:

> The following comparison chart shows all of the autofocus drive types that have ever been used in Canon's EF, EF-S, RF, and RF-S lenses.

They missed mentioning EF-M, Canon's foray into mirrorless interchangeable-lens cameras.

> Although the ultrasonic noise cannot be perceived by the human ear, it can be picked up by sensitive microphones which can be problematic during video shootings.

I used several Ring USM lenses and can hear the noise when focusing. It's a soft swishy kind of white noise, not harmonic. The Ring USM definitely generates noise in the audible range, not only ultrasonic.

> The latest types of autofocus drives, including the Stepper Motor, Nano USM, and Voice Coil Motor, offer focus-by-wire.

Though I have nothing against focus-by-wire on principle, the implementations have not been good. Having used several EF-M (all STM) and RF (some STM and some Nano USM) lenses that have focus-by-wire, I find that the motor actuation significantly lags behind the user turning the focus ring (which is a digital encoder), and the granularity of the focus steps are visible.

Meanwhile, the old EF Ring USM's full-time manual (FTM) was really good by comparison; it didn't take much force, was fully responsive with no lag, and was fully analog when turned by hand and had no discrete steps. I miss that, as new lenses don't use this design.

> Canon EF 15mm F2.8 Fisheye (et cetera)

Please change the syntax to "f/2.8"; this is even in Canon's official pages. https://global.canon/en/c-museum/product/ef263.html

Why? Because f is actually a lowercase italic variable that denotes the focal length (15 mm in this case), and "/" (slash) really means division. The size of the aperture is (15 mm / 2.8) = 5.4 mm; that is the real diameter of the hole that light passes through. The absolute aperture is 5.4 mm and the relative aperture is f/2.8. https://en.wikipedia.org/wiki/F-number

Re: Canon EF and RF Lenses – All Autofocus Motors

#73

Post by fusionadvocate »

ryandamm wrote: post #67

A note of possible interest for this crowd: all these motor types are open loop, so you can't actually command a specific state with any accuracy / repeatability. In other words, if you send a signal to the lens to focus at, say, 3m, it won't necessarily be in exactly the same state as the next time you focus at 3m. This is why camera calibration can be tricky, and you often don't want to touch the cameras after you'…

The system stops the motors once it reaches focus. Therefore is a closed loop system.

Re: Canon EF and RF Lenses – All Autofocus Motors

#74

Post by nayuki »

fusionadvocate wrote: post #73
ryandamm wrote: post #67

A note of possible interest for this crowd: all these motor types are open loop, so you can't actually command a specific state with any accuracy / repeatability. In other words, if you send a signal to the lens to focus at, say, 3m, it won't necessarily be in exactly the same state as the next time you focus at 3m. This is why camera calibration can be tricky, and you often don't want to touch the cameras after you'…

The system stops the motors once it reaches focus. Therefore is a closed loop system.

Correct. The AF sensor continually takes more samples even while the motor is moving. You can tell because sometimes the motor overshoots and then you can see it come back.

Re: Canon EF and RF Lenses – All Autofocus Motors

#76

Post by nayuki »

MartijnBraam wrote: post #20

I've always wanted to know how the various autofocus systems worked. This page is incredible. I wish there was another one with the Nikon autofocus systems since that's what I actually have. I still have several lenses with autofocus that don't have an AF motor in it at all, the motor is in the camera body instead there's a tiny screw on the lens mount that transfers the motor rotation to the autofocus parts in the l…

Nikon's lens/body compatibility matrix is horrendously complicated. https://www.kenrockwell.com/nikon/compatibility-lens.htm

Whereas I think "no metering" is never a problem on Canon.

Over the decades as a DSLR shooter (on Canon), I even saw Nikon shoot themselves in the foot not once but twice.

* When Nikon introduced "E" lenses (electronic aperture, like Canon and all modern designs), very few bodies were compatible with it. They didn't have the foresight to introduce compatible bodies before any lenses with E were released. For example, this was released in 2008 ( https://www.kenrockwell.com/nikon/24mm-pc.htm ), and the earliest compatible body is from 2007. It doesn't work with tons of crop (DX) bodies like the D90, as well as any film camera.

* When Nikon introduced "AF-P" (stepper motor) lenses in 2016, there were no compatible bodies before 2013. Again, not enough future-proofing.

Meanwhile, Canon took a different approach. They pissed off users twice - when transition from the FL mount (1964) to FD (1971), and FD to EF (1987). They basically got it all right with EF - fully electronic, no aperture slider, no focus screw, big diameter.

I have even successfully used a year-2017 Canon lens with Ring USM AF and IS on an original EOS 650 film body (released in 1987), and both AF and IS work perfectly. Mind you, both of those features did not even exist at the birth of EOS. Presumably the AF electronic protocol is agnostic of what motor technology is in the lens, and IS can be a lens-only thing without the body knowing.

Nikon's compatibility gotchas don't hold a candle to Canon's excellent (albeit imperfect) compatibility. Nikon keeps making the same mistakes over and over again, such as not having a screw-drive motor in the F to Z mount adapter; the company really seems to hate people with old lenses and bodies. Oh and this is not new either; Nikon's F to 1 adapter (does anyone remember that highly cropped mirrorless camera?) also lacked certain features.

Re: Canon EF and RF Lenses – All Autofocus Motors

#77

Post by MartijnBraam »

nayuki wrote: post #76
MartijnBraam wrote: post #20

I've always wanted to know how the various autofocus systems worked. This page is incredible. I wish there was another one with the Nikon autofocus systems since that's what I actually have. I still have several lenses with autofocus that don't have an AF motor in it at all, the motor is in the camera body instead there's a tiny screw on the lens mount that transfers the motor rotation to the autofocus parts in the l…

Nikon's lens/body compatibility matrix is horrendously complicated. https://www.kenrockwell.com/nikon/compatibility-lens.htm Whereas I think "no metering" is never a problem on Canon. Over the decades as a DSLR shooter (on Canon), I even saw Nikon shoot themselves in the foot not once but twice. * When Nikon introduced "E" lenses (electronic aperture, like Canon and all modern designs), very few bodies were compatibl…

What annoys me is that the AF-P could probably be supported on a lot more cameras, they did add it to the D3300 with a firmware update. They just didn't do it for more cameras...

Re: Canon EF and RF Lenses – All Autofocus Motors

#78

Post by contingencies »

sizzzzlerz wrote: post #54
exar0815 wrote: post #33

I always wanted to build a controller for Canon Telephoto lenses to use them with c-mount cameras and control the focus from a PC. Might be helpful for that.

A couple of universities built a telescope called Dragonfly, that utilizes 48 Canon 400mm lenses to photograph the skies of New Mexico. The kicker is they don't use camera bodies. Instead, they designed and built mounts that directly connect the lens to a sensor. A PC controls each lens through some custom electronics using commands they reverse-engineered from the Canon control software. These commands control focus…

I visited some similar telescope in Australia at https://www.sidingspringobservatory.com.au/ run by Macquarie University ... the students explained the lens system could not be too new and could not be too old. Basically it sounded like someone had partly reverse engineered one generation of the lens interface only.

I guess the camera and lens manufacturer wants their lenses to be used with their cameras and to have better results than other manufacturers, whereas random companies want to clone the interface and sell cheaper lenses that also work with the cameras. Realising how awesome the lenses are, the students want an array of them, however they don't have the budget to buy a similar array of top end manufacturers' cameras.

In Sydney they have interesting viewing nights at https://www.mq.edu.au/faculty-of-science-and-engineering/dep...

Re: Canon EF and RF Lenses – All Autofocus Motors

#79

Post by cpgxiii »

exar0815 wrote: post #33

I always wanted to build a controller for Canon Telephoto lenses to use them with c-mount cameras and control the focus from a PC. Might be helpful for that.

A number of machine vision camera vendors have higher-end variants that support active EF-mount lenses. They tend to be quite expensive models with larger sensor, since you tend to lose a lot adapting full-frame lenses to tiny C-mount sensors.

If you want a computer-controlled lens, one of the cheapest options is to use Blackmagic cameras that support SDI and/or USB control. You can then control either native M4/3 active lenses (focus, aperture, zoom) or supported EF-mount lenses if you use one of the EF->M4/3 active adapters.

Re: Canon EF and RF Lenses – All Autofocus Motors

#80

Post by ryandamm »

fusionadvocate wrote: post #73
ryandamm wrote: post #67

A note of possible interest for this crowd: all these motor types are open loop, so you can't actually command a specific state with any accuracy / repeatability. In other words, if you send a signal to the lens to focus at, say, 3m, it won't necessarily be in exactly the same state as the next time you focus at 3m. This is why camera calibration can be tricky, and you often don't want to touch the cameras after you'…

The system stops the motors once it reaches focus. Therefore is a closed loop system.

It’s open loop in that the measurement of it being in focus is reliant on the subject matter, and a different measurement.

I’m not making this up, camera manufacturers have told me to my face that focus is open loop, period. They can’t guarantee repeatable focus.

Notably the measurement isn’t of the state of the motor/gearing. Furthermore, being “in focus” means the subject matter’s out of focus blur is below some threshold; there is a range of focus states that qualifies — but those seemingly small differences can affect camera calibration, with >pixel-level differences in effective focal lengths.

It’s open loop.

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