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<blockquote data-quote="Clovishound" data-source="post: 845088" data-attributes="member: 50197">The rule of thumb is that in order to bring a non macro lens to 1:1 magnification, use extension tubes that equal the focal length of the lens. In the case you referenced, a 35mm lens will require 35mm of extension, based on the rule of thumb. To get 1:1 with my 180-600 at the longer end would require a whopping 600mm of extension. That's almost 2 feet for all the imperial measures folks. The 29mm of my two extension tubes gives me 1:1 at around 29mm with my 24-70 zoom, if I go much wider, I can't get close enough to the subject to focus, as BF pointed out. At the 70mm end, I don't nearly as much magnification.While most tubes are not available beyond 35mm, you can stack tubes. I have seen ridiculous stacks exceeding several feet. The bellows that BF pictured gives far more than 35mm of extension (the one I looked at online has 150mm of extension), so it definitely is doable. I'm not sure why manufacturers don't offer them in longer lengths. It may have more to do with marketing than physics.</blockquote>

[QUOTE="Clovishound, post: 845088, member: 50197"] The rule of thumb is that in order to bring a non macro lens to 1:1 magnification, use extension tubes that equal the focal length of the lens. In the case you referenced, a 35mm lens will require 35mm of extension, based on the rule of thumb. To get 1:1 with my 180-600 at the longer end would require a whopping 600mm of extension. That's almost 2 feet for all the imperial measures folks. The 29mm of my two extension tubes gives me 1:1 at around 29mm with my 24-70 zoom, if I go much wider, I can't get close enough to the subject to focus, as BF pointed out. At the 70mm end, I don't nearly as much magnification. While most tubes are not available beyond 35mm, you can stack tubes. I have seen ridiculous stacks exceeding several feet. The bellows that BF pictured gives far more than 35mm of extension (the one I looked at online has 150mm of extension), so it definitely is doable. I'm not sure why manufacturers don't offer them in longer lengths. It may have more to do with marketing than physics. [/QUOTE]

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