24-70/2.8 II L has a slight delay when auto-focusing, is it normal?

On my recently acquired EF 24-70/2.8 II L, I am noticing a slight delay when it's autofocusing. Maybe like approximately 300ms of "think time" before it then moves rather quickly and very accurately into focus-lock.

This is on a 6D, center AF point, one-shot AF and it's more noticable in lower-light scenarios.

Both my 24-105/4 L IS and 70-200/4 L IS do not show that delay, they start to move into focus pretty much immediately after I press the shutter (or back button focus) button. I've expected a better AF-performance than my 24-105 because of a) the price and b) the wider aperture of the 24-70.

Is this normal for this lens?

It is the camera's extra sensitivity AF module kicking in. The reason you don't experience it with f/4 lenses is that the module is only activated at f/2.8 and brighter.

Abu Mahendra wrote:

It is the camera's extra sensitivity AF module kicking in. The reason you don't experience it with f/4 lenses is that the module is only activated at f/2.8 and brighter.

Good info, I didn't know that. Could be part of the explanation why this lens produces so much ultra sharp images.

But does the high precision vertical sensitive AF that kicks in from f/2.8 and brighter needs extra time to do it's stuff?

Abu Mahendra wrote:

It is the camera's extra sensitivity AF module kicking in. The reason you don't experience it with f/4 lenses is that the module is only activated at f/2.8 and brighter.

That's interesting. Focusing is more or less instant with my 5D III bodies. What is this AF module thingie? Genuine request for info--no snark. Sounds like it would actually be a drawback for photographers needing to work fast.

Nickels wrote:

Kind of curious about that myself...? There always seems to be some reasoning for expensive lens issues (i.e the 85 f1.2 focuses slow because of all the glass....yet the 35L doesn't...?)
Curious about this explanation.

Right.  The 85L focuses by extending the large, heavy front lens group(s).  The 35L has inner focusing, moving a few small internal focus elements.

Re the 6D's AF system - Besides the standard precision cross center sensor, with f/2.8 and wider max aperture lenses it activates a high precision single axis sensor.  Other bodies are similar in this, but [wild guess] perhaps the lower light level the OP speaks of induces additional processing in the 6D, which has AF sensitivity rated to -3 EV, 1 stop greater than 5D III

The 6D focuses in lower light than the 5DIII. The 6D extra low light sensitivity module only kicks in in really low light.

Abu Mahendra wrote:

(..)The 6D extra low light sensitivity module only kicks in in really low light.

Now I am a little confused.

There's this one extra AF module with the vertical-line-sensitive AF point that is activated (only) if an f/2.8 or brighter lens is mounted. I got that.

Then there's another module that gets activated only in low-light situations? Or is the vertical-line-sensitive AF point module only activated on f/2.8 (or brighter) lenses and only in low-light situations?

Low light, near -3ev, AND f/2.8 or brighter.

larry wrote:

Abu Mahendra wrote:

The 6D focuses in lower light than the 5DIII. The 6D extra low light sensitivity module only kicks in in really low light.

Do you have a cite for this extra module, or is this just conjecture or misunderstanding?

No cite, just info based on use, confirmed by others here. The specs, however, are clear and explicit that the 6D can and does focus in lower light than the 5DIII. It's actually quite astounding how it will focus in virtual darkness. Coupled with IS and f/2 like with the 35IS, and it's something else.

Back to my original question:

Is anybody experiencing a slight delay / think time (~1/4th-1/3th sec) before the lens moves into focus in low-light with the 24-70/2.8 II?

In a normal to dimly lit room in the evening, focus on the far corner of the room and then point at something closer and press the shutter release. Does the lens start to move into focus instantly?

MutantLabs wrote:

Back to my original question:

Is anybody experiencing a slight delay / think time (~1/4th-1/3th sec) before the lens moves into focus in low-light with the 24-70/2.8 II?

In a normal to dimly lit room in the evening, focus on the far corner of the room and then point at something closer and press the shutter release. Does the lens start to move into focus instantly?

Back to my original answer. Yes, i too experience it with said lens as well as with other f/2.8 or brighter lenses. I have already provided the explanation. Nothing out of order or broken. Normal behaviour.

never heard of or experienced any delay of any kind.

MutantLabs wrote:

Back to my original question:

Is anybody experiencing a slight delay / think time (~1/4th-1/3th sec) before the lens moves into focus in low-light with the 24-70/2.8 II?

In a normal to dimly lit room in the evening, focus on the far corner of the room and then point at something closer and press the shutter release. Does the lens start to move into focus instantly?

Back to my original answer. Yes, i too experience it with said lens as well as with other f/2.8 or brighter lenses. I have already provided the explanation. Nothing out of order or broken. Normal behaviour.

Ah, ok. I missed the point that you are experiencing the delay as well. Thanks!
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