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]

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

[amfoto1]

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

[deebatman316]

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

[amfoto1]

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

[deebatman316]

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