Another DSLR Focus question
 

How many of you are using auto focus during the ceremony on bright days? I find this to be a must. Yes, it over exposes for a few seconds but I just edit those 2 seconds out and have piece of mind that I'm sharp. Keep in mind that I'm using it only on subjects that are somewhat standing still.

Do you mean auto focus? Do you mean auto exposure? You shoot weddings on auto exposure? Hiss of air drawn in through clenched teeth. White dresses and dark suits are no place to be pointing idiot auto exposure mechanisms at. Strange English, but you get my drift.

tom.

Not auto exposure. Most SLR's will overexpose your shot for a few seconds when you hit the AFON button in record mode. A guy on Youtube explains this here:
YouTube - Autofocus in Movie Mode on the Canon 5D Mark II

I was just wondering if anyone uses this technique during the ceremony.

That's a new one on me Ian - thanks for the news. I might say that even really really cheap 1080 camcorders don't do that.

Ian: my apologies for a snarky comment posted here earlier which I have
since removed from public view. I wish people would take questions
at face value and not try to second-guess a poster's intentions.

The question clearly refers to auto-focus, not auto-exposure. When
shooting in Live View mode with Live View focus assist initiated, the
D-SLR will change exposure briefly in order to provide enough contrast
in the image for auto-focus to read. Then the image returns to the
original user-set exposure.

The reason why really cheap 1080 camcorders don't do that is
because they're not Digital SLR's with Live View. In other words,
they don't work the same way (I thought we were all clear on that).

Back to Ian, it all comes down to a pretty basic question: are you
going to be able to shoot for the edit? Since that AF mode bumps
the exposure and adds audible noise, you know you'll have to edit
that out later... but can you shoot around that? As fast paced and
not easily repeatable as a lot of event videography is, I'm not so
certain that I would be able to manage it. The alternative, focusing
manually on the fly, is not all that appealing either. I've always
thought that D-SLR's are perfect for carefully planned, repeatable
set-ups such as filmmaking, but in my opinion it's rolling the dice
a bit to use them for event videography (unless of course you're
really, really good at it -- which I'm most definitely not)!

Focusing, re-focusing etc all come down to what you can and can't edit out and how confident you are in the current focus points.

The biggest problem with DSLRs for weddings (and events in general) is that in low light settings at longer focal lengths you would typically have to open up the aperture or increase the ISO dramatically. Opening up the aperture leads to significant loss of depth of field, which in turns makes it difficult to keep focus on people who are moving about.

DSLRs simply can't compete with regular camcorders for good DOF at long focal lengths in low light. Any one who thinks they can should go test the DSLRs against something like an HMC 150/151/152 etc.

This means you need to be on the ball for focus at all times. There are three ways to auto-focus a DSLR such as the 7D (only 2 on the 5D).

• Manually (great in good light - can be hit and miss in low light)

• Using the AF button when not recording (causes the mirror to flip and a beep to be emitted)

• Using the AF button while recording - essentially silent to those around you, but it interferes with video (and sound) (not available on the 5D)

The question of whether you can ride the AF button is one we have been playing with. There are two different scenarios when riding the AF button makes sense

• When you need to be quiet (no mirror flip)

• When the subject is moving and you need to keep an eye on them

While the mirror flip allows for the normal focus points to be used, you lose sight of the subject, so you could miss focus if they moved during the focus time.

So, yes there are times we would use this, but certainly not all the time. Using auto focus on the camcorders is however not something we would ever use in a ceremony or during the speeches. Too much opportunity for the camera to focus on the back wall instead!

Ian. I have used auto focus on my 7D just for the vows. While the bride and groom are getting into place, you can auto focus. (that is not footage you would use anyway). Otherwise, I manually focus all day. I love to manually focus because I can decide exactly what I want in focus, and what I don't want in.

I normally use manual focus lenses so the auto-focus trick does not work. In that case, I stop recording, pull up the x5 and x10 magnification, refocus as necessary, and start recording again. It creates a gap in the recording but I don't mind as I usually have another camera and separate double system sound to rely on. It's better to have a 5-10 second gap and be confident you nailed focus, than not doing it and finding out later in post you were out of focus for 10 minutes.

Or you could use a smaller aperture (deeper DOF) and bump up ISO accordingly as necessary.