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Message: <blockquote data-quote="denco@comcast.n" data-source="post: 3199683" data-attributes="member: 25300">DOF is more complicated than it seems and some feel focal ratio, eyepiece design, field curvature and exit pupil, as well as magnification can all play a role in how good a binoculars DOF is. Depth perception is definitely better in a porro than a roof simply because of the greater spatial separation of the barrels. Here is good thread on DOF from Cloudy Nights where a lot of knowledgeable people discuss DOF and why some binoculars seem better. Here is a quote from the thread explaining why porro's appear to have better DOF even though optical theory does not suggest they should."The only optical parameter which determines depth of field is the magnification. Its influence is huge, because of the 2-power of M in the equation. Now, why people find that binoculars with equal magnification have quite different depth of field ? I think that the perceived depth of field in binoculars is determined by other parameters than optical ones. Here are two examples : I think that the collimation of the binocular can play a role. When we are looking at near objects, for reading for instance, our eyes are accustomed to converge and simultaneously accommodate. Maybe if the images in the binocular are slightly convergent, the eyes are encouraged to instinctively accommodate on near objects. If I'm right, porro prism binocular should be better than roof prisms, because apart from very distant objects, the wider objective separation makes the two images more convergent than in a roof prism binocular. Another explanation can be the curvature of field : its practical consequence is that objects in focus off-axis are closer to the binocular than objects in focus on-axis. Now, when the binocular is aimed at a distant target in a landscape, nearly all the objects in the image closer than the target appear off-axis. If there is some curvature of field, we can have the illusion of a great depth of field, because the distant object on-axis appears in focus at the same time that closer objects off-axis. I think the best way to verify the strictly optical depth of field is to examine objects only in the centre of the field, and with only one eye, in order to avoid human eye and brain compensations." <a href="http://www.cloudynights.com/topic/17656-depth-of-field/" target="_blank">http://www.cloudynights.com/topic/17656-depth-of-field/</a></blockquote>

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