Anyone notice Contrast Detect AF works better with a set point?
/forum/topic/1155707/0



FlyPenFly
Registered: Feb 14, 2011
Total Posts: 6446
Country: United States

Anyone notice Contrast Detect AF works better with a set point?

In both the NEX and Olympus OM-D.

With the OM-D its definitely a lot faster to AF with something like a MMF-3 and Oly 14-54mm Mk2 to lock focus with a set AF box. I also think it's faster when using other lenses as well.

I tried this again with my NEX-7 and C3 (much harder to do because both lack touch screens. I used my ZA 24mm and Sigma 19mm.

Is it in my head or does anyone else notice the same thing?

I manually racked focus to one extreme when I refocused.



douglasf13
Registered: Apr 09, 2008
Total Posts: 6080
Country: United States

Hmmm, I'd think so, but I'm not sure. I've never actually used anything other than a set AF point with my mirrorless cameras.



Joseph Marney
Registered: Jan 11, 2002
Total Posts: 1417
Country: United States

douglasf13 wrote:
Hmmm, I'd think so, but I'm not sure. I've never actually used anything other than a set AF point with my mirrorless cameras.


Same here. It makes sense to me that it would be faster, but I always do it that way anyway....



FlyPenFly
Registered: Feb 14, 2011
Total Posts: 6446
Country: United States

In my head, I would assume there is some speed gain on the processor side since it only has to scan a much smaller area for highest contrast and it also doesn't have to sort of guess where you wanted the AF point.

However, if it guessed racking the lens the wrong direction, wouldn't it still go through the full range of the lens so essentially it becomes limited by lens speed? But on top of that, perhaps the algorithm is smart enough to realize it's going the wrong way before switching direction?



httivals
Registered: May 08, 2004
Total Posts: 980
Country: United States

Yes, I've noticed it's faster. It makes sense to me. I've assumed the faster speed is because the processor doesn't first need to apply an algorithim to the data to determine which focus point to automatically select.



jonrock
Registered: Jan 03, 2012
Total Posts: 444
Country: United States

I've also noticed this as well. It's kind of why I wished the Nex 6 had a touchscreen to select a set point faster.