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understanding DOF
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<blockquote data-quote="WayneF" data-source="post: 491350" data-attributes="member: 12496"><p>I have heard of the Canon Auto Bellows, but never seen one. The Nikon macro lenses do that too, automatically compensate to show the correct f/stop number for the extension. I suspect your 28-80G does that too? (I've never seen one).</p><p></p><p>There is a mir page at <a href="http://mir.com.my/rb/photography/companies/nikon/nikkoresources/AFNikkor/AF2880mm/index.htm" target="_blank">NIkon Autofocus (AF) Zoom Nikkor 28-80mm f/3.5~5.6D lens group - Index Page</a> on the earlier D lens, which just mentions the G. It was an inexpensive lens, no distance scale, plastic mount and plastic filter threads.</p><p></p><p>Ken Rockwell has a page (he's usually good on specs), <a href="http://www.kenrockwell.com/nikon/28-80mm-g.htm" target="_blank">Nikon 28-80mm f/3.3-5.6G</a></p><p></p><p>Both say it focuses a little closer than most lenses, about 14 inches, to 1:3.5 magnification (not nearly 1:1, but closer than most lenses). Rockwell says minimum aperture is f/22 - f/38. He does not say if that f/38 is reported, or just actual (but probably is reported at this date You'd know what it does).</p><p></p><p>The usual nomenclature for a <span style="font-family: 'Arial'">f/3.5-5.6 lens is that maximum is 3.5 at wide angle zoom, and f/5.6 at maximum zoom. Several lenses do this. This one also focusing closer has another possibility, of a smaller aperture up close (both wide and tele).</span></p><p><span style="font-family: 'Arial'"></span></p><p><span style="font-family: 'Arial'">You could determine what it does...</span></p><p><span style="font-family: 'Arial'"></span></p><p><span style="font-family: 'Arial'">With a subject more distant, say 20 feet (doesn't really matter, but not close)</span></p><p><span style="font-family: 'Arial'">At maximum aperture (f/3.5), zoom to widest angle and focus and note reported aperture.</span></p><p><span style="font-family: 'Arial'">Should say 3.5.</span></p><p><span style="font-family: 'Arial'">Also at maximum aperture, zoom in to longest telephoto and focus and note reported aperture.</span></p><p><span style="font-family: 'Arial'">Should say 5.6.</span></p><p><span style="font-family: 'Arial'"></span></p><p><span style="font-family: 'Arial'">Then repeat at minimum aperture, which should say f/22 wide, but I don't know tele. I think most today would say f/22 tele too. The problem isn't that they cannot stop down, but they cannot open wider than maximum.</span></p><p><span style="font-family: 'Arial'"></span></p><p><span style="font-family: 'Arial'">Then at closest distance (14 inches), repeat both wide and telephoto.</span></p><p><span style="font-family: 'Arial'">At closest distance, my guess is both wide and tele report a little larger number, due to the closeup magnification.</span></p><p><span style="font-family: 'Arial'">Or it seems possible that it might report some combination of the two effects.</span></p><p><span style="font-family: 'Arial'"></span></p><p><span style="font-family: 'Arial'">But I'd guess that in any situation, the lens is doing what it reports it is doing.</span></p><p><span style="font-family: 'Arial'"></span></p><p><span style="font-family: 'Arial'"></span></p><p><span style="font-family: 'Arial'"></span></p><p><span style="font-family: 'Arial'"></span></p></blockquote><p></p>
[QUOTE="WayneF, post: 491350, member: 12496"] I have heard of the Canon Auto Bellows, but never seen one. The Nikon macro lenses do that too, automatically compensate to show the correct f/stop number for the extension. I suspect your 28-80G does that too? (I've never seen one). There is a mir page at [url=http://mir.com.my/rb/photography/companies/nikon/nikkoresources/AFNikkor/AF2880mm/index.htm]NIkon Autofocus (AF) Zoom Nikkor 28-80mm f/3.5~5.6D lens group - Index Page[/url] on the earlier D lens, which just mentions the G. It was an inexpensive lens, no distance scale, plastic mount and plastic filter threads. Ken Rockwell has a page (he's usually good on specs), [URL="http://www.kenrockwell.com/nikon/28-80mm-g.htm"]Nikon 28-80mm f/3.3-5.6G[/URL] Both say it focuses a little closer than most lenses, about 14 inches, to 1:3.5 magnification (not nearly 1:1, but closer than most lenses). Rockwell says minimum aperture is f/22 - f/38. He does not say if that f/38 is reported, or just actual (but probably is reported at this date You'd know what it does). The usual nomenclature for a [FONT=Arial]f/3.5-5.6 lens is that maximum is 3.5 at wide angle zoom, and f/5.6 at maximum zoom. Several lenses do this. This one also focusing closer has another possibility, of a smaller aperture up close (both wide and tele). You could determine what it does... With a subject more distant, say 20 feet (doesn't really matter, but not close) At maximum aperture (f/3.5), zoom to widest angle and focus and note reported aperture. Should say 3.5. Also at maximum aperture, zoom in to longest telephoto and focus and note reported aperture. Should say 5.6. Then repeat at minimum aperture, which should say f/22 wide, but I don't know tele. I think most today would say f/22 tele too. The problem isn't that they cannot stop down, but they cannot open wider than maximum. Then at closest distance (14 inches), repeat both wide and telephoto. At closest distance, my guess is both wide and tele report a little larger number, due to the closeup magnification. Or it seems possible that it might report some combination of the two effects. But I'd guess that in any situation, the lens is doing what it reports it is doing. [/FONT] [/QUOTE]
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