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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

#141

Post by ExAr »

nayuki wrote: post #140
ExAr wrote: post #98

Earlier quoted context omitted.

Thanks nayuki for the detailed comment and positive feedback. Thanks for pointing out the missing EF-M, I am going to add that during the next polishing round. With regards to USM noise, the ultrasonic whine can be picked up by very good ears. I think the Nano USM is excited in the range of 60+ kHz, so at least that type of USM motor is absolutely inaudible. Syntax-wise with F2.8, you got me. I know it's not 100% cor…

> With regards to USM noise Here is a video showing the "whooshing" noise of Ring USM, and it is clearly in the audible range (not ultrasonic): https://imgur.com/a/canon-ring-usm-autofocus-sound-YCrV1CR > the relation between the focal length and the f-number is known by every photographer I'm going to disagree with this. I think very few photographers understand what an absolute aperture size is. Here's a good test:…

Thanks for following this up.

I have checked the video you've linked. My suggestion would be that this whooshing noise is not generated by the piezoelectric part but rather from the connected focusing mechanism (especially the helical focusing barrel which turns, and the focusing lens cell which slides back and forth. These parts sit inside the stationary lens barrel, and so a bit of friction is unavoidable. Just my guess.)

Syntax-wise, I will have to think about it. As with all my other articles, I like being very precise with physical formulas and mathematical expressions. But here is my point: These values in photography are not pinpoint precise anyway. When optical engineers come up with lens designs, the precisely calculated values for the aperture are something like f/4.63 which is then simply rounded to the next possible f-value specified on the lens barrel, and calculated focal length is often 25-49mm and Canon simply names that lens 24-50mm on the barrel (other manufacturers do that in a similar way). So, this is just my personal opinion, but it appears to me that in the context of photography, these values are just halfway decent guide values, almost like approximate descriptions of the lens behaviour. For that reason, I do understand why lens manufacturers move away from the precise syntax, and treat these values more like an abstract product description. Of course, if used in a strictly scientific context, I would rather prefer to use f/4.5. But I might be pretty alone with this view.

PS: I have planned a new chapter explaining all this, including the interesting fact that you've mentioned, where the diameter of the exit pupil actually changes according to the focal length, even with a constant aperture lens. But it will probably be end of summer when this is going online.

Re: Canon EF and RF Lenses – All Autofocus Motors

#142

Post by nayuki »

ExAr wrote: post #141
nayuki wrote: post #140

Earlier quoted context omitted.

> With regards to USM noise Here is a video showing the "whooshing" noise of Ring USM, and it is clearly in the audible range (not ultrasonic): https://imgur.com/a/canon-ring-usm-autofocus-sound-YCrV1CR > the relation between the focal length and the f-number is known by every photographer I'm going to disagree with this. I think very few photographers understand what an absolute aperture size is. Here's a good test:…

Thanks for following this up. I have checked the video you've linked. My suggestion would be that this whooshing noise is not generated by the piezoelectric part but rather from the connected focusing mechanism (especially the helical focusing barrel which turns, and the focusing lens cell which slides back and forth. These parts sit inside the stationary lens barrel, and so a bit of friction is unavoidable. Just my…

> this whooshing noise is not generated by the piezoelectric part but rather from the connected focusing mechanism

Indeed. I never implied that the piezoelectric part makes an audible whooshing noise. I only meant to say that the entire Ring USM system makes that noise, and so it will affect audio recorded on the camera's on-board microphone. Either way, that noise explains the motivation for the development of STM AF and I guess Nano USM.

Agreed with everything else you said. Thanks again for your fantastic articles and replies!

Re: Canon EF and RF Lenses – All Autofocus Motors

#143

Post by lofaszvanitt »

porphyra wrote: post #115
post_break wrote: post #105

Canon is dead to me after they forced 3rd parties to stop all RF lenses. I bought the last AF lens by Viltrox and it's fantastic. I regret getting an RF body after they threatened them, and now only allow 3rd parties on their crop sensor bodies. Fuji, Sony, Leica, Nikon, all allow 3rd party lenses. I switched to Fuji and won't go back.

It is a little sad honestly how Canon has now been surpassed by Sony in both sensor technology and lens optical quality and yet they double down on forcing people to use their expensive lenses. I miss the old days when EF mount was the lingua franca of autofocus mounts with a thriving ecosystem of lenses from Sigma, Tamron, and the like. Even now some of the Sigma Art lenses for SLR mounts, like the 40mm and 105mm f/…

Well, they had some very bad financial years behind them. They will let third parties, but it will take time to recuperate losses.

Re: Canon EF and RF Lenses – All Autofocus Motors

#144

Post by roblh »

formerphotoj wrote: post #133
SAI_Peregrinus wrote: post #109

Earlier quoted context omitted.

The a9 iii shoots 120FPS 24.6MP raw files with continuous autofocus and without blacking the viewfinder. Top-end cameras are insane .

I sort of miss my Canon EOS 1 at 10 fps (film) when shooting sports. "If you saw it, you missed it."

The $$$ per second of shooting that is hilarious. I guess that’s what shooting IMAX feels like, but only for like 3 and a half seconds at a time.

Re: Canon EF and RF Lenses – All Autofocus Motors

#145

Post by tonyarkles »

vladvasiliu wrote: post #123
tonyarkles wrote: post #103

Earlier quoted context omitted.

I can back you up on that. I work on a highly custom system that uses EF lenses through an EF-to-serial adapter. The lenses don't even know what position they're at when you power them on. If you want to move them to a specific focus step you have to go through a homing procedure that drives the focus motor to a stop (I don't recall if it's the near or far stop). Lens-to-lens it's definitely not consistent. Step 142…

How could they then tell to what distance they're focused? I used to have two Ultrasonic lenses, the 17-40/4L and the 17-55/2.8. They both had distance scales which would move around as the lens focused. My current Olympus lenses have a focus-by-wire manual mode, with a distance scale on the barrel. The camera also reports the focus distance in the EXIF. Are these just vague ballparks?

Sorry for the late reply. What we’ve found is that they’re all close but not identical. Our system has a point LIDAR pointed at the ground and then uses that to drive the focal distance for the lens (as well as input for some other sensor fusion stuff). We generally run the lenses wide open (f/2.0 or f/2.8). Mapping step counts to distance would get us close, but unless we did calibration for each individual lens it wasn’t close enough to get the focus tack sharp. When you’re looking at the focal distance in your EXIF metadata you’re probably not validating whether that 2.4m distance to the subject was actually 2.3m and for the vast majority of cases the absolute accuracy of it doesn’t matter. Same with the distance markers on the focus ring… you’re not setting the focus within a few cm based on those marks, just getting it close enough that you can do closed-loop focusing with an eyeball in the loop.

Once we did the per-lens calibration curve we didn’t have to do it again. I’m assuming the small differences are just manufacturing tolerance and they’re relying on the focus/phase sensors to get it the rest of the way.

Re: Canon EF and RF Lenses – All Autofocus Motors

#146

Post by KetoManx64 »

dboreham wrote: post #124
post_break wrote: post #105

Canon is dead to me after they forced 3rd parties to stop all RF lenses. I bought the last AF lens by Viltrox and it's fantastic. I regret getting an RF body after they threatened them, and now only allow 3rd parties on their crop sensor bodies. Fuji, Sony, Leica, Nikon, all allow 3rd party lenses. I switched to Fuji and won't go back.

Also not pleased that third party lens vendors were excluded. However the way I look at this is perhaps we would have no Canon cameras at all if the revenue they derive from lenses had not been captured.

They just slightly prolonged their death spiral. Lots of very negative press and potential buyers going to their competition now

Re: Canon EF and RF Lenses – All Autofocus Motors

#147

Post by Wistar »

roflmaostc wrote: post #119
porphyra wrote: post #115

Earlier quoted context omitted.

It is a little sad honestly how Canon has now been surpassed by Sony in both sensor technology and lens optical quality and yet they double down on forcing people to use their expensive lenses. I miss the old days when EF mount was the lingua franca of autofocus mounts with a thriving ecosystem of lenses from Sigma, Tamron, and the like. Even now some of the Sigma Art lenses for SLR mounts, like the 40mm and 105mm f/…

Yes, Sigma ART lenses are insane for that price. Also, they look very elegant compare to plastic Canon lenses. I was hoping for the new Sigma BF camera, simple and elegant. Unfortunately no Bluetooth, which is a deal breaker for me.

I recently purchased my first non-Canon lens for my Canon 5D, a Sigma 105mm f1.4 Art with EF mount. I bought it specifically for bokehrama (Brenizer method) work—mostly car stuff. It’s comically big and heavy and I have read of people having lens failures but, oh wow, it makes beautiful images at a focal length I love.
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