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Photography Q&A
Does standing further back & zooming in increase the acceptable focus zone?
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<blockquote data-quote="WayneF" data-source="post: 550777" data-attributes="member: 12496"><p>I'll try to help then.</p><p></p><p>Yes, where we stand does affect the perspective of the overall scene, from the different viewpoint of where we stand to look. This makes discussing images with the "same subject size" be vague and iffy. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p><p></p><p>But computed DOF depends on four factors:</p><p>numeric f/stop number</p><p>focal length</p><p>focused distance</p><p>and sensor size.</p><p></p><p>You are ignoring and leaving out distance. But (for same size subject) if we use a 2x longer lens, then we have to stand back 2x farther, which are opposite effects, largely canceling each other out, DOF wise (same subject size too). All other things are not equal.</p><p></p><p> Check any DOF calculator, a good one is</p><p><a href="http://www.dofmaster.com/dofjs.html" target="_blank">Online Depth of Field Calculator</a></p><p></p><p>At the defaults at which it first comes up, it shows the DOF at 10 feet has an overall DOF range of 6.61 feet.</p><p></p><p>Change 10 feet to 20 feet and DOF range changes to 38.5 feet (a very large difference).</p><p></p><p>But then also change the default 55mm focal length to 110 mm (for same subject size), and the range is back to 6.15 feet.</p><p></p><p>Not precisely opposite and equal (degree will vary with the numbers), but very nearly so. The percentage in front and in back are still more different than the sum of the range. The hyperfocal distance is quite different. So it's pretty hard to argue "same DOF", but it is vaguely ballpark close, might satisfy a quick check in some cases.</p><p> </p><p>And yes, of course the perspective due to where we stand is different too.</p><p></p><p>Focal length matters.</p><p></p><p>Distance also matters. One of four factors that matter.</p></blockquote><p></p>
[QUOTE="WayneF, post: 550777, member: 12496"] I'll try to help then. Yes, where we stand does affect the perspective of the overall scene, from the different viewpoint of where we stand to look. This makes discussing images with the "same subject size" be vague and iffy. :) But computed DOF depends on four factors: numeric f/stop number focal length focused distance and sensor size. You are ignoring and leaving out distance. But (for same size subject) if we use a 2x longer lens, then we have to stand back 2x farther, which are opposite effects, largely canceling each other out, DOF wise (same subject size too). All other things are not equal. Check any DOF calculator, a good one is [URL="http://www.dofmaster.com/dofjs.html"]Online Depth of Field Calculator[/URL] At the defaults at which it first comes up, it shows the DOF at 10 feet has an overall DOF range of 6.61 feet. Change 10 feet to 20 feet and DOF range changes to 38.5 feet (a very large difference). But then also change the default 55mm focal length to 110 mm (for same subject size), and the range is back to 6.15 feet. Not precisely opposite and equal (degree will vary with the numbers), but very nearly so. The percentage in front and in back are still more different than the sum of the range. The hyperfocal distance is quite different. So it's pretty hard to argue "same DOF", but it is vaguely ballpark close, might satisfy a quick check in some cases. And yes, of course the perspective due to where we stand is different too. Focal length matters. Distance also matters. One of four factors that matter. [/QUOTE]
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Photography Q&A
Does standing further back & zooming in increase the acceptable focus zone?
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