But one does not have to equalize the reproduction ratio by capturing
the same size image on film or sensor. One can do it in post processing
as long as the lens is capable of a sufficiently small CoC to withstand
the additional magnification. That was what I did in my first example.
I used 100mm at 10 feet with a CoC of 30 lines/mm and a 50mm lens at
10 feet with a suitable CoC for a 4/3 sensor of 60 lines/mm. Using a
conventional DOF calculator shows that the 50mm has much more DOF.
Chuck Norcutt
On 12/19/2010 12:57 PM, Jan Steinman wrote:
>> From: "C.H.Ling"<ch_photo@xxxxxxxxxxxxx>
>>
>> I do think it is the sensor gives the increased DOF not the lens,
>> for the same magnification, a 50mm lens and 100mm lens have the
>> same DOF under the same aperture but the one with smaller sensor
>> gives deeper DOF.
>
> I was going to just leave Chuck to his delusion, but I must agree:
> DOF is determined by aperture and reproduction ratio -- period.
>
> The focal length changes DOF only to the extent that, unless you move
> the camera closer or farther from the subject, focal length changes
> the reproduction ratio. As C.H. notes, for the same subject size, a
> 50mm lens and a 100mm lens have the same DOF at the same aperture.
>
> ---------------- We should take care not to make the intellect our
> god; it has, of course, powerful muscles, but no personality. --
> Albert Einstein :::: Jan Steinman, EcoReality Co-op ::::
>
--
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