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Message: <blockquote data-quote="ronh" data-source="post: 1530008" data-attributes="member: 55514">Thanks to all for this interesting discussion. Might as well chip in my little bit of confusion. Although I am certainly one of their unwitting victims, I don't know what to say, do, or think about the things that masquerade as DOF, so I will confine my statements to the bona fide variety.Formulae for DOF from photography can be simply modified from film grain to eyepiece and visual acuity. I have done this, and the results are generally consistent with most people's experience that big, low powered binoculars have the greatest DOF. But, I have not made any measurements.I agree with Jean-Charles that the individual's focus accomodation is not accounted for in the mechanical relationships from photography. (Gee, I wish I had focus accomodation. My eyes are so stiff, I am practically a camera.) For me, the eye pupil opening is a major effect. In bright daylight, my 7x50 seems to have a very nice DOF and focus is forgiving. But at night, striving to separate the closest double stars, I find that I must focus within a relatively narrow 0.2 diopter range for the best results.Finally, I have a nutty idea that might help understand the m-squared formula intuitively. Higher magnifications show a more detailed picture of the scene, so it is easier to see a small focusing error. This contributes to the perception that higher magnifications have a shallower view, but only gives a factor of m. The size of the defocus blur, for a given linear defocus (ie, for a given mm of motion of the focusing element), scales with magnification, giving another factor of m. Thus, m-squared. Ron</blockquote>

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