50mm STM Lens Focus Ring Won't Focus

[Radiux]

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? 

[deebatman316]

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

[BrianDavies]

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.

[MikeSowsun]

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

[deebatman316]

@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

[Radiux]

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 😅

[deebatman316]

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

[MikeSowsun]

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.

[deebatman316]

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

[Waddizzle]

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