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Message: <blockquote data-quote="Kevin Purcell" data-source="post: 1311351" data-attributes="member: 68323">Interesting point, Herman. I wonder if that leads to so many conflicting view on the DOF. It changes the perception of the DOF but the physical DOF is still the same but the young observer can move that DOF around in the view i.e. a young observer can make the whole field look "in focus" but the portion he is fixated on will be in focus. For example the young observer should be able to bring the branches in front of and behind the bird into focus. And this is why fixed focus (and semi-fixed like independent focus) bins work well for younger users.BTW, for those that want to estimate their accommodation range try this:<ol> <li data-xf-list-type="ol">Wear eyeglasses to correct your distance vision (bifiocal wearers don't use the reading segment for this test)</li> <li data-xf-list-type="ol">Determine the distance you can clearly see an object close to you (bring it up to your eyes and measure the distance fromit to your eyes)</li> <li data-xf-list-type="ol">Your accommodation is about 1/D diopters for D in meters (or 39/D in inches)</li> </ol>For example, I'm 47 year old myope (short-sighted) who needs reading glasses (+1.5D add) have an accommodation of about 1.9 diopters. Not great. I won't be changing my depth of field too much. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite2" alt=";)" title="Wink    ;)" loading="lazy" data-shortname=";)" />However all that said I do have a collection of bins with the same magnification and the same aperture and they have different DOFs (with my same older low accommodation eyes ... that's a constant). In some cases it's difficult to determine why they have the DOFs they have e.g. the Celestron Ultima DX 8x32 porro has the worst DOF of all my 8x bins even though it has a small objective and I think quite a long focal length (i.e. a larger f/number objective) it is quite clearly worse than my 8x40ish bins. So I'm quite sure there are other optical factors in the DOF in some of these bins. BTW, this bin has quite large field curvature at the edge of field (and wide FOV 8.2 degrees) so it's not a field flattener issue!Like stray light, DOF is not something that appears on a spec sheet and so is difficult to estimate without a hands on review.</blockquote>

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