Re: [OM] More on DOF and focal length (by Ctein)

[Chuck Norcutt [Permanent Link]]

But I'm afraid you haven't exactly proven your case.

Chuck Norcutt

Ken Norton wrote:
>> Normally said as "all wet" rather than "completely wet".  At least I
>> think that's what he meant.  See definition #2 here:
>> <http://en.wiktionary.org/wiki/all_wet>
>>
> 
> 
> I think his conclusion is correct, but the path to get there is wrong. The
> math does not match his assumptions--especially in the discussion about
> cropped image vs longer focal-length. This is when his theories break down
> because as Chuck has clearly stated, in order to calculate DoF you must work
> from a known output size (magnification).  Ctein is using "non-test tests to
> figure this out and is being fooled by how different optical designs can
> alter other imaging characteristics which can be misinterpreted as an
> increase/decrease in DoF.
> 
> AG
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