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Re: [OM] Focus Accuracy Test - Oh what misery we bring uponourselves

Subject: Re: [OM] Focus Accuracy Test - Oh what misery we bring uponourselves
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Mon, 16 Aug 2010 17:15:05 -0400
I'm not sure where you came up with that CoC number.  It's incredibly 
tight at about 5 times what's required for a good 8x10 print.  But it 
does serve to demonstrate the point.  Even at extreme resolution the DoF 
exceeds the 5-6 meter range.

Chuck Norcutt


C.H.Ling wrote:
> I'm not sure if 5D II has poorer liveview than L1 but based on the DOF 
> calculator:
> 
> http://www.dofmaster.com/dofjs.html
> 
> If I set CoC to 0.006mm (35mm/5616pixel), object distance 5.5 meter, the DoF 
> is 4.74m to 6.56m. It indicates one cannot differentiate the focus between 5 
> and 6 meter, or I have missed something?
> 
> C.H.Ling
> 
> ----- Original Message ----- 
> From: "Ken Norton" <ken@xxxxxxxxxxx>
> 
>> As to the 5D Mk2's live-view--it is my understanding that this camera
>> doesn't use all pixels for live-view and skips pixels. This, again,
>> would get you in the neighborhood but is anything, but exact. To
>> differenciate a focus point at 5 vs. 6 meters with a "normal" focal
>> length, the difference with most lenses is a whisper of a nudge. Like
>> C.H. says, 0.5mm or so. The problem is that wide-open, there is
>> usually just enough CA or other issues with the lens which prevents
>> precise focusing to this level. As mentioned, stopping down the 24mm
>> F2.8 lens to F4 acually make precise focusing more feasable. The
>> line-pairs on the usaf lit up like a Christmas Tree when in focus. I
>> could conclude, therefore, that it is possible the L1 has a superior
>> live-view than the 5Dmk2.
> 
> 
-- 
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