how to avoid jerky zoom shift while shooting videos?

[rama]

Hi!

Recently I purchased EOS 70D with kit lens (EF-S 18-55 STM) and tele-zoom (EF-S 55-250 STM). Both lenses give excellent result for still photos.

But while video shooting, I notice considerable jerk in the video due to adjustment in the zoom ring of the lenses. Less noticeable nuissance in the video if I make sudden turn of the zoom ring but very much noticeable while making slow & gradual shift on the zoom ring. Thus an inferior video result in comparison to cheaper cameras that have TELE / WIDE zoom buttons! As such the zoom ring is quite free to rotate & no mechanical defect on the lens body.

Any suggestioins please?  

[amfoto1]

Do you have IS on? Perhaps IS is trying to "correct" the zooming movement. You might do a test with it turned off. I don't use that lens or shoot video, so this it just a guess.

***********
Alan Myers

San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & PRINTROOM 

[TCampbell]

In professional video they REALLY RESIST the urge to "zoom" while shooting.  I wont say it's "never" done... it is, but it's something that should be done sparingly as zooming in general is very distracting.  

If you want a professional result, you can pre-plan focus changes and zoom changes prior to shooting the clip.

Pro videographers will go far as to wrap a piece of masking or gaffers tape around the lens ring, and put marks on focus or zoom positions (which were pre-tested before the shot).  When they're ready to perform the zoom or focus change, they can visually look at the marks and do a smoother transition from one mark to the next.

For a really really professional result... the camea is mounted on a rail or boom and the zoom ring isn't touched at all.

Keep in mind these lenses are not "parfocal" which means if you set it to any given focal length, focus it to your satisfaction, then zoom to a different focal length, the lens will require re-focusing (there are only a few true "parfocal" lenses where the focus does not change at all as you zoom.)