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[OM] Re: DOF - Digital versus analogue

Subject: [OM] Re: DOF - Digital versus analogue
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Mon, 04 Dec 2006 18:45:12 -0500
I don't know how film is getting into the equation here and can't 
understand your first paragraph.  I agree, lenses is lenses is lenses 
and, I also agree, there is no difference between film and digital.

But what the Wikipedia article addressed was a difference in focal 
length... and aperture.  The increased depth of field comes from the 
shorter focal length and has nothing to do with the medium.  100mm f/2.8 
vs. 50mm f/1.4.  Put these on film or digital and blow up equal coverage 
angles with appropriate resolution adjustment to account for the 
difference in magnification to make the same prints and you will get 
*identical* depth of field at two stops difference.

The math doesn't lie.  The calculator offer still stands.

Chuck Norcutt


Bill Pearce wrote:
>>You'll find that the DOF is identical using the numbers below from the
>>Wikipedia article.
> 
> I simply can't understand why doubling the magnification on film gives a one 
> stop improvement and on digital you get two. The lens is the same
> 
> Let's take this farther. going back to film, the dof of a 100mm lens is the 
> same as the equivlent crop from a 50mm taken from the same point. Will it 
> then be double that on digital?
> 
> Why does the different medium count? Lenses are lenses are lenses.
> 
> Bill Pearce 
> 
> 
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