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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: 550845" data-attributes="member: 12496"><p>I don't know what to tell you. I guess block me on your Ignore List if it is of no use to you. I always thought questions wanted actual factual answers, not just some wild notions. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /> Circle of Confusion is simply how it works, which has been known for nearly 200 years. I'd call it a basic. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /> Not First Day stuff, but a basic about DOF.</p><p></p><p>Actually, the rocket science comment was instead agreeing with Stoshowicz that a wider lens does show things smaller, which does make it look sharper, since the blurred detail is far too small to see. That hardly seems like rocket science to me. <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></p><p>I frankly think the photos of the girl on the bridge are NOT achieved by standing back at greater distance. The article never stated that there was any standing back. It would have been a very appreciable distance, worthy of comment. And because it is a standard fact that standing back and zooming in to same subject size is said to "appear to be" about the same depth of field. I say "appear to" which that would, but there are details that dispute the preciseness of it. Nevertheless, "same size has same DOF" is an old notion that it is certainly ball park true. It's very easy to find it said. Sparky is saying it. <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 this bridge DOF stuff does not come close to what real work would show if standing back for same size. There had to be a little (14 to 200mm), but it was NOT the goal. Cropping achieved the same size in that example. There is no offsetting DOF increase due to standing back. The depth of field (the ground level rivets) is clear evidence it is <strong>done by cropping</strong>, not by standing back.</p><p></p><p>Judging the field height by roughly guessing the girls height, standing back would require:</p><p></p><p>12mm 7 feet height at 5.3 feet. - DOF calculates 2.1' in front, 10' behind (using f/4 as stated)</p><p>35mm 6 feet height at 13.4 feet. - DOF calculates 2.1' in front, 3' behind</p><p>100mm 6 feet height at 38 feet. - DOF calculates 2.3' in front, 2.6' behind</p><p>200mm 6 feet height at 77 feet. - DOF calculates 2.4' in front, 2.6' behind</p><p></p><p>Then achieving same size with the greater distance increasing the DOF, and a longer lens decreasing DOF, then we would have seen approximately similar DOF. But this obviously did not happen. Not even close.</p><p></p><p>To the authors credit, he never says "standing back", he only mentions zooming. That was a false assumption made in this thread, assuming this example was "standing back". Clearly it is not. It does not claim it. </p><p></p><p>So then lens focal length does what was claimed and shown, without any opposite compensation due to standing back farther. However then the cropping introduces a significant enlargement factor difference, which is the confusion factor here. DOF is about as much about enlargement factor as any of the conventional factors. In practice, you may want to stand back more instead of cropping, to keep your image pixels.</p><p></p><p></p><p>Anyway, if it HAD BEEN standing back with a longer lens to achieve the same subject height, then DOF ought to be roughly similar. That was not the case in the example shown here.</p></blockquote><p></p>
[QUOTE="WayneF, post: 550845, member: 12496"] I don't know what to tell you. I guess block me on your Ignore List if it is of no use to you. I always thought questions wanted actual factual answers, not just some wild notions. :) Circle of Confusion is simply how it works, which has been known for nearly 200 years. I'd call it a basic. :) Not First Day stuff, but a basic about DOF. Actually, the rocket science comment was instead agreeing with Stoshowicz that a wider lens does show things smaller, which does make it look sharper, since the blurred detail is far too small to see. That hardly seems like rocket science to me. :) I frankly think the photos of the girl on the bridge are NOT achieved by standing back at greater distance. The article never stated that there was any standing back. It would have been a very appreciable distance, worthy of comment. And because it is a standard fact that standing back and zooming in to same subject size is said to "appear to be" about the same depth of field. I say "appear to" which that would, but there are details that dispute the preciseness of it. Nevertheless, "same size has same DOF" is an old notion that it is certainly ball park true. It's very easy to find it said. Sparky is saying it. :) But this bridge DOF stuff does not come close to what real work would show if standing back for same size. There had to be a little (14 to 200mm), but it was NOT the goal. Cropping achieved the same size in that example. There is no offsetting DOF increase due to standing back. The depth of field (the ground level rivets) is clear evidence it is [B]done by cropping[/B], not by standing back. Judging the field height by roughly guessing the girls height, standing back would require: 12mm 7 feet height at 5.3 feet. - DOF calculates 2.1' in front, 10' behind (using f/4 as stated) 35mm 6 feet height at 13.4 feet. - DOF calculates 2.1' in front, 3' behind 100mm 6 feet height at 38 feet. - DOF calculates 2.3' in front, 2.6' behind 200mm 6 feet height at 77 feet. - DOF calculates 2.4' in front, 2.6' behind Then achieving same size with the greater distance increasing the DOF, and a longer lens decreasing DOF, then we would have seen approximately similar DOF. But this obviously did not happen. Not even close. To the authors credit, he never says "standing back", he only mentions zooming. That was a false assumption made in this thread, assuming this example was "standing back". Clearly it is not. It does not claim it. So then lens focal length does what was claimed and shown, without any opposite compensation due to standing back farther. However then the cropping introduces a significant enlargement factor difference, which is the confusion factor here. DOF is about as much about enlargement factor as any of the conventional factors. In practice, you may want to stand back more instead of cropping, to keep your image pixels. Anyway, if it HAD BEEN standing back with a longer lens to achieve the same subject height, then DOF ought to be roughly similar. That was not the case in the example shown here. [/QUOTE]
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Does standing further back & zooming in increase the acceptable focus zone?
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