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Re: [OM] Eos-M

Subject: Re: [OM] Eos-M
From: Moose <olymoose@xxxxxxxxx>
Date: Fri, 02 Nov 2012 21:29:00 -0700
On 11/2/2012 2:57 PM, usher99@xxxxxxx wrote:
> I just don't get this one.  Perhaps Canyon's first toe in the water.
> They don't really have an APS-C sensor to blow out the competition out
> of the water and no EVF or articulated screen.  It does nicely use Canyon EF 
> lenses
> though with IS/AF but the AF performance is just not there.
>
> http://www.lensrentals.com/blog/2012/10/eos-m-first-impressions

It seems that Canon's designers and marketers were caught in an impossible 
situation - and managed to bring a 
semi-functional compromise camera to market. Technically, the silliest thing to 
come out of Canon for a very long time. 
 From a sales standpoint, who knows?

When Roger says "If they fix the AF speed with a firmware update ..." It seems 
that he has already forgotten much of 
what he wrote about CD & PD AF in July 2010. Although now dated in some ways, 
it's still a nice explanation. 
<http://www.lensrentals.com/blog/2010/07/how-autofocus-often-works>

The basic situation is that lenses designed for PDAF physically can't focus 
very fast on CDAF. The types of focus motors 
they have and the mass of the moving parts are ill suited for it.

Pretty much everybody but Canon has been finding strategies to adjust to the 
change.

Oly has jumped with both feet on the alternate of completely new engineering of 
lenses specifically optimized for CDAF, 
with very small, light moving elements and different motors. That they can 
claim the E-M5 to be the 'fastest focusing' 
something or other, and my personal experience, show that this strategy works. 
As a side benefit, they especially silent 
focusing for video. I assume Panasonic must be doing something similar, 
although their decision to go with in-lens IS 
may make it harder.

Sony (and Nikon?) has designed sensors with a few special sites to do phase 
detection, allowing fast movement in one 
step to at least close to accurate focus with conventional lens AF mechanisms. 
I say 'close' because they do final focus 
with CDAF. Although they trumpet this dual mode as a positive feature, I 
suspect it is necessary because the on-chip PD 
sensors don't work as well as a full fledged DSLR PDAF system.

This would be a great solution for Canon, allowing the EOS-M to use their huge 
array of EF lenses effectively. The 
reality of the EOS-M shows that they don't have a hybrid PD sensor chip ready. 
No firmware upgrade is going to change 
the basic problem.

Just why the native lenses for the EOS-M are still slow, although not as badly 
so, I don't know. Perhaps the whole thing 
is just a stopgap measure until they bring out an alternate solution to 
mirrorless use of their EF lenses. In which 
case, they may have ported existing lens optical and mechanical designs for the 
new camera with the minimum redesign 
expenditure.

CDAF Moose

-- 
What if the Hokey Pokey *IS* what it's all about?
-- 
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