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Re: [OM] E-450

Subject: Re: [OM] E-450
From: Andrew Fildes <afildes@xxxxxxxxxxxxx>
Date: Wed, 1 Apr 2009 17:02:48 +1100
Thanks for that - the reason i asked is that on the press releases an  
specs., previous models have stated explicitly that Contrast  
Detection AF is available in LiveView - the E-450 does not, just the  
Contrast Detection AF Mode is available. It struck me that it may be  
possible to enable it in regular shooting where appropriate, but I  
can't find confirmation.
Andrew Fildes
afildes@xxxxxxxxxxxxx



On 01/04/2009, at 10:54 AM, Chuck Norcutt wrote:

> Contrast measurement is implemented entirely within the sensor and is
> used on point and shoots and focusing in live view with the mirror up
> (and shutter open, of course)  Phase detection is used in SLRs and  
> DSLRs
> when not in live view.  Phase detection uses a beam splitter to  
> form and
> compare two images.  Phase detection can tell if an out-of-focus image
> is either back or front focused and start driving the lens immediately
> in the right direction to achieve focus.  It's faster than conrast
> measurement which may have to hunt a bit to get started.  But, while
> slower, contrast measurement is potentially more accurate.
>
> "Shutter open" above assumes there is an actual mechanical shutter  
> that
> needs to be opened.  That's not necessarily true.  There may only  
> be an
> electronic shutter which, again, is implemented within the electronics
> of the sensor.  Or there may be both mechanical and electronic  
> shutters
> as in my Mynolta A1.
>
> See the nitty-gritty in this Wiki article
> <http://en.wikipedia.org/wiki/Autofocus>
>
> Chuck Norcutt
>
>
> Andrew Fildes wrote:
>> Indeed. But they are sticking with 'small'.
>> It appears to me that Contrast Detection AF has been used only in
>> Live View so far but is now an available mode for normal shooting.
>> Have I got that right? Anyone know the advantage?
>> Andrew Fildes
>> afildes@xxxxxxxxxxxxx
>>
>>
>>
>> On 01/04/2009, at 8:46 AM, Donald wrote:
>>
>>>> Is the 420 Contrast Detection AF - I'll have to go check. That's
>>>> developed for the Micro 4/3rds system.
>>>> I did expect them to get IS into it though - using the reduced size
>>>> IS module and circuit board from the 620.
>>>> Andrew Fildes
>>>> afildes@xxxxxxxxxxxxx
>>>>
>>> Yes, that would have been nice. At the entry level it kinda makes
>>> sense, no?
>>
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