topic Re: Canon 50mm stm newbie question in EF & RF Lenses

50mm STM Lens Focus Ring Won't Focus

Radiux — Thu, 29 Dec 2022 13:52:57 GMT

Hi everyone!

A few days ago I bought a brand new canon 50mm stm lens, which by the way takes beautiful pictures.

I practice photography as a hobbie so Im by no means an expert on lenses and cameras but something has been bothering me since I bought it:

When I set the lens to manual focus, sometimes the focus ring will not focus (camera turned on) no matter how much I move the ring. The only thing that seems to "wake it up" is half pressing the shutter and then it works as supposed... Until it happens again...

To me it seems like a power saving function, but it feels counter intuitive imho, as it makes me think that something may be wrong with the lens.

Autofocus works fast and without any problems btw.

Camera is also a brand New rebel t7

Any ideas?

Re: Canon 50mm stm newbie question

deebatman316 — Wed, 28 Dec 2022 23:39:32 GMT

Hello Radiux welcome to the forum and happy holidays. I also own the EF 50mm F/1.8 STM lens. All STM and Nano USM lenses are Focus by Wire/ utilize and Electronic Focus Ring. The camera metering system MUST be active for the electronic focus ring to work. You're lens is working as designed and there isn't a problem with it. Does Manual Focus Override work correctly too. Click Here for the manual for your lens. Click Here for the manual for your camera.

-Demetrius

Happy Holidays

EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 28-135mm F/3.5-5.6 IS USM (Retired), EF 50 F/1.8 STM, EF 85mm F/1.8 USM & EF 70-200mm F/2.8L IS III USM

EOS 40D (Retired) & 5D Mark IV

430EX III-RT, 470EX-AI & 600EX II-RT

Re: Canon 50mm stm newbie question

BrianDavies — Wed, 28 Dec 2022 22:35:15 GMT

It sounds like it is working "as designed". When the exposure settings disappear in your viewfinder, the camera is going into a semi-sleep mode and needs to be woken up before you can do anything. So half-pressing the shutter button will wake it up to either autofocus, or now allow you to manually focus. I think your lens is working fine.

Re: Canon 50mm stm newbie question

MikeSowsun — Wed, 28 Dec 2022 22:53:55 GMT

Simply switching the lens to MF will make the electronic focus ring active at all times, without having to half press the shutter.

Re: Canon 50mm stm newbie question

deebatman316 — Wed, 28 Dec 2022 23:38:16 GMT

@MikeSowsun I just tested my EF 50 F/1.8 STM with the lens set to manual focus. I tested the lens on 2 bodies the 5D Mark IV and an old EOS 40D. On both bodies I couldn't manually focus unless the viewfinder display was active. So I do not believe your statement was correct regarding the electronic focus ring.

-Demetrius

Happy Holidays

EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 28-135mm F/3.5-5.6 IS USM (Retired), EF 50 F/1.8 STM, EF 85mm F/1.8 USM & EF 70-200mm F/2.8L IS III USM

EOS 40D (Retired) & 5D Mark IV

430EX III-RT, 470EX-AI & 600EX II-RT

Re: Canon 50mm stm newbie question

Radiux — Wed, 28 Dec 2022 23:41:12 GMT

Wow, I can't believe how fast you guys answered with excellent and informative comments!!!

Thanks Demetrius and Brian for the answers and the links provided! I'll definitely Stick around this community and next time I'll read the manual before asking questions 😅

Re: Canon 50mm stm newbie question

deebatman316 — Wed, 28 Dec 2022 23:47:46 GMT

Canon provides electronic manuals of all of their products free of charge.

-Demetrius

Happy Holidays

EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 28-135mm F/3.5-5.6 IS USM (Retired), EF 50 F/1.8 STM, EF 85mm F/1.8 USM & EF 70-200mm F/2.8L IS III USM

EOS 40D (Retired) & 5D Mark IV

430EX III-RT, 470EX-AI & 600EX II-RT

Re: Canon 50mm stm newbie question

MikeSowsun — Thu, 29 Dec 2022 01:42:09 GMT

Here is what I have noticed with all my STM lenses:

In One-Shot Auto Focus, the focus can be fine tuned (Full Time Manual focus) anytime the shutter is half pressed. As soon as you take your finger off the shutter the STM AF goes dead. (really more like part-time manual focus) 😉

In AI Servo Auto Focus the focus ring is always dead and you can't do manual focus over-ride or fine tune the focus.

In Manual focus the focus ring will be active while your finger is on the shutter button, OR while the metering is active. It will also continue to operate with your finger off the shutter button, but the lens will "go to sleep" after approximately 5 seconds after the metering stops. You won't be able to focus again until you half-press the shutter and start the metering.

But......If you continually adjust the focus ring, the STM Manual Focus will continue to operate for as long as you keep moving it. (even long after the metering has stopped). If you stop adjusting the focus ring, the lens will go to sleep again after 5 seconds. A quick tap on the shutter button starts the metering again and the STM focus will operate again.

Re: Canon 50mm stm newbie question

deebatman316 — Thu, 29 Dec 2022 02:13:07 GMT

I noticed on my old 40D the electronic focus ring is active at all times in live view. But this camera doesn't support on image sensor AF. I ASSUME its setup this way because the shutter button doesn't allow AF while in live view only the "AF-On" button does. The camera DOES allow quick AF while in live view. I haven't tested my 5D Mark IV to see how STM and Nano USM lenses works in live view. I ASSUME it works the same way. The EF 85mm F/1.2L I/ II USM lens is a USM with an electronic focus ring.

-Demetrius

Happy Holidays

EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 28-135mm F/3.5-5.6 IS USM (Retired), EF 50 F/1.8 STM, EF 85mm F/1.8 USM & EF 70-200mm F/2.8L IS III USM

EOS 40D (Retired) & 5D Mark IV

430EX III-RT, 470EX-AI & 600EX II-RT

Re: Canon 50mm stm newbie question

Waddizzle — Thu, 29 Dec 2022 16:00:32 GMT

With one exception, I believe all Canon DSLR STM lenses are EF-S lenses, not EF.

Re: Canon 50mm stm newbie question

deebatman316 — Thu, 29 Dec 2022 18:57:51 GMT

Actually Canon makes 3 full frame EF lenses. The EF 40mm F/2.8 STM, EF 50mm F/1.8 STM and the Canon EF 24-105mm F/3.5-5.6 IS STM Lenses.

-Demetrius

Happy Holidays

EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 28-135mm F/3.5-5.6 IS USM (Retired), EF 50 F/1.8 STM, EF 85mm F/1.8 USM & EF 70-200mm F/2.8L IS III USM

EOS 40D (Retired) & 5D Mark IV

430EX III-RT, 470EX-AI & 600EX II-RT

Re: 50mm STM Lens Focus Ring Won't Focus

amfoto1 — Thu, 29 Dec 2022 18:00:15 GMT

In simple terms, all Canon STM (stepper motor) lenses are "fly-by-wire".

This means they utilize electronic servos to focus... even when using the manual focus ring.

For this reason, the camera must be "powered up" and active before it's possible to focus the lens, whether that's done manually or with the AF system. The camera can be powered up by half-press of the shutter release or, on the cameras that have it, by pressing the "AF On" button under your thumb (or another button that's been assigned to that function).

Wadizzle is correct. There is only the one EF (full frame for Canon DSLRs) lens: the EF 50mm f/1.8 STM being discussed here There are currently five EF-S (APS-C) lenses using STM: One prime, four zooms.

All seven current EF-M lenses for the Canon M-series mirrorless cameras use STM. Those are all APS-C camera and lens designs, and they include three primes and four zooms.

Out of 30 Canon lenses total (so far), nine of the RF (full frame) and two RF-S (APS-C) lenses for the Canon R-series mirrorless cameras use STM. Seven of those RF lenses are primes and two are zooms. Presently both of the RF-S lenses are zooms.

I seem to recall that there may be some "Hybrid USM" lenses that are also fly-by-wire. I don't know if they require the same camera activation to allow manual focusing, but wouldn't be surprised if they did.

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7DII (x2), 7D(x2), EOS M5, some other cameras, various lenses & accessories
FLICKR

Re: 50mm STM Lens Focus Ring Won't Focus

deebatman316 — Thu, 29 Dec 2022 18:55:47 GMT

Actually that is Not true Canon has made 3 EF (Full Frame) STM lenses. The EF 40mm F/2.8 STM, EF 50mm F/1.8 STM and the EF 24-105mm F/3.5-5.6 IS STM. Canon does make Nano USM lenses which are focus by wire.

-Demetrius

Happy Holidays

EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 28-135mm F/3.5-5.6 IS USM (Retired), EF 50 F/1.8 STM, EF 85mm F/1.8 USM & EF 70-200mm F/2.8L IS III USM

EOS 40D (Retired) & 5D Mark IV

430EX III-RT, 470EX-AI & 600EX II-RT

Re: 50mm STM Lens Focus Ring Won't Focus

amfoto1 — Thu, 29 Dec 2022 19:53:22 GMT

Hi,

We're both correct.

You're using past tense, while I used present tense in my earlier response.

In total, Canon has made three full frame EF lenses with STM.

But they've discontinued the 40mm and the 24-105mm,...

So presently there is only one: the EF 50mm f/1.8 STM.

Cheers!

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7DII (x2), 7D(x2), EOS M5, some other cameras, various lenses & accessories
FLICKR

Re: 50mm STM Lens Focus Ring Won't Focus

deebatman316 — Thu, 29 Dec 2022 20:13:21 GMT

I didn't know that they discontinued both of those lenses.

-Demetrius

Happy Holidays

EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 28-135mm F/3.5-5.6 IS USM (Retired), EF 50 F/1.8 STM, EF 85mm F/1.8 USM & EF 70-200mm F/2.8L IS III USM

EOS 40D (Retired) & 5D Mark IV

430EX III-RT, 470EX-AI & 600EX II-RT