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Autofocus Juddering - Canon 60 D - Sigma 30mm 1.4

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Caleb Trevatt
Autofocus Juddering - Canon 60 D - Sigma 30mm 1.4
on Mar 7, 2012 at 10:14:12 am

Here's a quick clip my friend and I filmed.
If there isn't something wrong, it's virtually unusable.

If anyone has any feedback or suggestions, please don't hesitate to tell.

-- Caleb

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John Young
Re: Autofocus Juddering - Canon 60 D - Sigma 30mm 1.4
on Mar 7, 2012 at 3:41:36 pm

First question is, Why are you using auto-focus while recording?
DSLRs (with the exception of the Sony Alphas) will NOT do any sort of auto focus while recording. At least not any that renders the shot usable while the auto-focus process takes palce. This has nothing to do with the lens (although the Sigma may auto focus slower and louder than some others). Even a high end L lens auto focuses the same way that your Sigma does.
That being said, in the course of my career, there are only a few specific situations where I am using the camera's auto focus while recording, even when I am using an actual video camera like an EX-1. In the vast majority of situations I am manually setting the focus either before recording begins or manually pulling focus mid-shot.
The simple solution to your problem is just to focus BEFORE you press record, if you are going to use auto-focus at all. With a DSLR I am almost always using those great 5x and 10x maginifcation buttons to get focus, before I roll on the shot.


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Rob Manning
Re: Autofocus Juddering - Canon 60 D - Sigma 30mm 1.4
on Mar 9, 2012 at 4:30:18 am

Hi Caleb,

Using AF is not an ideal technique while rolling.

The function causes two issues, the noise from the motor aligning the iris blades, and the OOF portion while the CPU resolves the focus points.

IF, you are shooting say near a loud source (guitar amps) and using the on-board audio, then the motor will likely be a non issue, but, an off camera shotgun or other mic into a discrete DAR is the proven method for audio.

The Out Of Focus instant or two, can be mitigated if the editing technique is anticipating that moment of focus loss.

It is NOT the best method while shooting, and will need to be cut out in post, perhaps with a slide or still inserted in the clip to mask that moment.

An example of that is here,

From a trade show recently where I knew the lens would be refocused during a performance but had planned for that and did insert context during the edit.

After a while, gear like a follow focus, rails, and especially a monitor to check for blown out highlights and focus BEFORE recording begins each become part of the kit for every shoot.



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