DPReview.com is closing April 10th - Find out more

Manually focused lens gives blurred images and then sharp images - without being touched

Started Jun 28, 2015 | Discussions thread
Lemming51
Lemming51 Forum Pro • Posts: 15,278
normal. peculiarity of STM
1

GreenPig wrote:

I have been taking photos at a dance show rehearsals using two camera – sat at one of them framing and shooting, whilst the other camera was on a tripod fired by a hand-held wireless control.

The remote one was a 350D with 18-55STM lens – the lens set to manual focus and test shots were perfect. But when I fired the remote, about 1 in 4 shots is blurred.

It seems like the lens adjusts focus temporarily whilst the shot is taken. A subsequent shot a coulple of seconds later it perfectly sharp.

I wondered if the camera had gone into sleep mode and then when I fired the remote, it woke up. During the wake up, the electronic focusing was still adjusting – despite being switched to manual.

Throughout the few hours shooting I did not adjust the lens at all - so after a blurred shot, the lens returned to the correct focus setting.

see p. 4 of the instruction manual for the EF-S 18-55 f/3.5-5.6 IS STM.  The STM lens has it's own sleep mode, and does a focus re-set when it wakes up.  Need to wait a second or so after waking the lens for it to return to the set focus.

http://gdlp01.c-wss.com/gds/8/0300011908/02/efs18-55f35-56isstm-im2-eng.pdf

Seems counter-intuitive that power on/off would have any affect if the lens is set to manual focus, but remember that with STM even manual focus is powered and not a direct mechanical connection to the focus ring.

-- hide signature --

Unapologetic Canon Apologist

 Lemming51's gear list:Lemming51's gear list
Canon EOS 40D Canon EF 50mm F1.8 II Canon EF-S 15-85mm f/3.5-5.6 IS USM Canon EF 70-200mm f/2.8L USM Canon EF-S 55-250mm f/4-5.6 IS STM +5 more
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow