Does FL effect DOF for the same Magnification? Going nuts here!

[Doug Kerr]

Hi, Helmuth,

If I'd been quick enough to respond to your second-last posting,
where you said:

Accordingly, as a review of my original paper on this topic had suggested, > the equation currently stated on the Dofmaster site for the far distance > appears to be in error. I believe that it should be (using their notation):
Df = (s(H-f)) (H-s-2f)
not
Df = (s(H-f)) (H-s) ,

I would've observed that the first form cannot be correct since,
when s=H, by definition, Df has to be infinite and this is not the
case with that form.

Well, indeed, and of course I should have noted that.

Of course, in the correct forms, the arrangements with regard to "F" come about from the fact that in the generalized expression, the denominator includes the construction "-f±f", which of course comes out to -2f in one situation and drops out in the other.

Anyhow, it's gratifying that we've got all this sorted out in the end!

Absolutely. Thanks again for your assistance in this regard.

And I am delighted to have your compact forms for the near and far DoF, which of course can be readily blown back to forms for the near and far limits that do not require the intermediate determination of H!

I plan to include coverage of all that when I rework my paper on depth of field to correct the error in it. You will of course be implicated in the acknowledgments!

Best regards,

Doug