I'm not confused and I'm not trying to change the test. But I could not
see any difference in the test that he did. But I thought that test was
more stringent than it needed to be. I allowed a one meter separation
(from 5 to 6 meters) and he didn't use it. One meter should make it
easier to dispute my claim.
Chuck Norcutt
Moose wrote:
> On 8/14/2010 4:31 PM, Chuck Norcutt wrote:
>> No, the distances were not arbitrary. If you go back and read my
>> original post on this subject and (I think) my last comment, the
>> distances were chosen such that an error of 1 meter in focusing would
>> alter the total DoF by a considerable amount. From 5 to 6 meters on the
>> zoom at 24/3.2 the DoF gets extended by 5 meters on the long side. It
>> was intentionally sized to say you can't claim extra DoF for the lens
>> since, at that distance, you can't focus accurately enough to say they
>> were actually focused at the same distance.
>
> Wait a minute here. Yes indeed, the original question involves DOF. However,
> this test is simply about whether AG can
> accurately focus within a specified difference of subject distance. The
> choice of a shorter difference of subject
> distances does not invalidate this particular test.
>
> IF - the test proves that AG can focus over a narrower distance than you
> specified, it also proves he can do so over the
> longer distance.
>
> Your specified distances may still be correct for the DOF test, but don't get
> the two tests confused.
>
> As you have separately posted, you don't agree with me that the test
> succeeded, but that doesn't change the fact that if
> it did, it proves the focus differentiation/accuracy point quite nicely.
>
>> If you can't claim exactly the same focusing distance (within a given error
>> range) you can't claim
>> unusual DoF behavior on the part of the lens.
>
> I agree.
>
> Moose
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