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[OM] Re: [OT] A brief Tokina 28-80 test note

Subject: [OM] Re: [OT] A brief Tokina 28-80 test note
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxx>
Date: Wed, 31 May 2006 19:53:57 -0400
Since it's a DSLR (and not an E-330) the rear screen is not live during 
focusing.  I know the plane of focus is not flat but if I'm focusing 
correctly the center part of the image (which is what I focused on) 
should be sharp while the edges might not be.  Instead, I found the 
opposite to be true.

I know, the conclusion is that I'm not focusing correctly.

Chuck Norcutt

tOM Trottier wrote:

> On Wednesday, May 31, 2006 at 14:40,
> Chuck Norcutt <olympus@xxxxxxxxxx> wrote:
> 
> ...
> 
>>So far I've only analyzed the results for 28mm but here's what I've
>>seen so far.  The first startling observation is that every single
>>autofocus shot on the Tokina looks better than the corresponding
>>manual focus shots on the same lens.  Not by a great deal but enough
>>so that you'd readily pick one over the other.  That was a bit of a
>>shock.  I don't know if it's my eyes or the screen but it's a fact.
> 
> 
> I'd get the screen or camera checked, or the adjustment of any dioptre 
> adapter.
> 
> 
>>The next shock was that I rated the performance of the Kiron 28-70/4
>>as "unacceptable" at center from f/4 thru f/8 and "poor" at the
>>edges through f/8.  It didn't produce what I'd call a decent image
>>until f/11 and was still performing better at the edges than center.
> 
> ...
> 
> That does sound like a focus error since the "plane of focus" is often a 
> sphere or parabola.
> 
> Does the 5D have a display and magnify function for the rear screen during 
> manual focus? - an 
> electronic VariMagni? You could try bracketing focus slightly, then magnify 
> the results.
> 
> tOM
> 
> --
> tOM Trottier, Ottawa, Canada
>       758 Albert St, Ottawa ON Canada K1R 7V8 
>       +1 613 231-6115 N45.412 W75.714
> http://groups.yahoo.com/group/ottawa-photo-clubs
> "The moment one gives close attention to anything, 
> even a blade of grass, it becomes a mysterious, 
> awesome, indescribably magnificent world in itself "
> -- Henry Miller, 1891-1980
> 
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