On 8/11/2012 6:56 AM, Carlos J. Santisteban wrote:
> Hi Moose and all,
>
>
> From: Moose <olymoose@xxxxxxxxx>
>
>> but where it's CDAF will focus in a complex, 3D subject is just 'different'
>> than with Canon PDAF.
I still find this to be true.
>> Example: A bee on the dark center of a sunflower. With the Canons, centering
>> the central focus point on the bee would focus on the bee. The OM-D and
>> 14-150 focused on the surface of the flower.
Here, I believe I may have misunderstood the effect of operator error. The way
the E-M5 indicates an attempt to focus
closer than the lens will go is somehow different than I was used to. I had the
camera set to take a shot even if focus
could not be achieved, as I had been playing with how OOF shots looked with
this lens/camera.
I now think that what happened with these particular shots was that the bee was
just slightly too close for the lens to
focus on, it focused as close as it could, I didn't properly note the lack of
confirmation beep/flash, and the above
setting let me go ahead and shoot out of focus.
I've now got the camera set to refuse to fire without focus confirmation. :-)
> The great difference between both AF systems is that PDAF, much like a
> human with a split-screen, usually "knows" if a particular object within
> the AF area is in focus, back-focused or front-focused. It seems they're
> designed to focus on the closest object inside the AF area, leaving the
> rest beyond the focus plane.
Yes, although often moving the central spot around and refocusing will get what
I want. That depends, of course, on
vision acute enough to see the effect in the viewfinder.
> On the other hand, CDAF (which works more like a matte screen) has no idea
> at all -- it just moves the focusing mechanism back and forth and keeps
> comparing the apparent sharpness of whatever lies on the AF area. If the
> measured sharpness/contrast is going _down_, it reverses the focusing
> direction, until contrast goes down again -- supposedly after reaching the
> focus point.
>
> But if the objects inside the AF area are located at different distances,
> the one who contributes "more" to that perceived sharpness (be it because
> of contrast, pattern, colour, orientation... whatever) will "win" the CDAF
> quest...
Yes. As a result, it will sometimes focus at a random appearing depth in a
complex, deep, 3D subject. I've run into that
on a few occasions. Again, not necessarily 'bad', but different from PDAF.
On the up side, I discovered S-AF[MF] focus mode. A half press of the shutter
release, or press of a function button set
to AF, focuses, and fine tuning may be done with the MF ring.
This is very much like the nicer Canon lenses that allow MF adjustment without
switching out of AF mode.
I like!!
MF AF Moose
--
What if the Hokey Pokey *IS* what it's all about?
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