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<blockquote data-quote="WayneF" data-source="post: 365391" data-attributes="member: 12496">Again, extension tubes allow lenses to focus CLOSER than their normal close focus limit.&nbsp;&nbsp; We rack a lens out to focus close, and the extension tube also racks them out.&nbsp;&nbsp; That is what these two pictures do (owl and watch), focus close. The magnification is simply due to being closer to them.&nbsp;&nbsp; The owl and the watch pictures are relatively close, certainly NOT at infinity.&nbsp; Extension tubes will no longer focus at far distances, like infinity, so would be useless for wildlife at most distances.&nbsp; Instead, that is what teleconverters do.&nbsp; &nbsp; A 1.4x teleconverter adds one stop to the aperture settings, and a 2x adds two stops.The Magnification of an extension tube adds two stops at 1:1 magnification, much less at much smaller magnifications.f-stop number = focal length / aperture diameter.When focal length doubles, then f-stop number doubles, which is two stops.Extension tubes are fairly short ... 10mm to 40mm.... and have minor effect on long lenses like 300mm or 600.&nbsp;&nbsp; They have a tremendous effect on short lenses, like 24mm.For more, search Google for Extension Tube Math</blockquote>

[QUOTE="WayneF, post: 365391, member: 12496"] Again, extension tubes allow lenses to focus CLOSER than their normal close focus limit. We rack a lens out to focus close, and the extension tube also racks them out. That is what these two pictures do (owl and watch), focus close. The magnification is simply due to being closer to them. The owl and the watch pictures are relatively close, certainly NOT at infinity. Extension tubes will no longer focus at far distances, like infinity, so would be useless for wildlife at most distances. Instead, that is what teleconverters do. A 1.4x teleconverter adds one stop to the aperture settings, and a 2x adds two stops. The Magnification of an extension tube adds two stops at 1:1 magnification, much less at much smaller magnifications. f-stop number = focal length / aperture diameter. When focal length doubles, then f-stop number doubles, which is two stops. Extension tubes are fairly short ... 10mm to 40mm.... and have minor effect on long lenses like 300mm or 600. They have a tremendous effect on short lenses, like 24mm. For more, search Google for Extension Tube Math [/QUOTE]

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