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<blockquote data-quote="Bob Blaylock" data-source="post: 572492" data-attributes="member: 16749">Using my D3200, my 18-55mm “kit lens”, and my generic set of extension tubes, (12mm, 20mm, 36mm), I have found that I can still get autofocus with any one of these tubes, and with any combination of two of them except the 20mm and the 36mm).&nbsp; So, up to 48mm of extension, I get autofocus, at 56mm or more, I don't.&nbsp; I guess I should count myself lucky I get any autofocus at all.&nbsp; The manual for my D3200 specifies that autofocus requires a largest effective aperture of at least ƒ/5.6.&nbsp; The extension tubes are only really useful with the lens zoomed in to 55mm, at which ƒ/5.6 is the largest effective aperture of the lens by itself, and surely adding any extension tubes must have the effect of reducing the effective aperture somewhat; so when I am using my extension tubes, and getting autofocus, then at that point, I have my camera performing beyond the limits that Nikon claims for it.</blockquote>

[QUOTE="Bob Blaylock, post: 572492, member: 16749"] Using my D3200, my 18-55mm “kit lens”, and my generic set of extension tubes, (12mm, 20mm, 36mm), I have found that I can still get autofocus with any one of these tubes, and with any combination of two of them except the 20mm and the 36mm). So, up to 48mm of extension, I get autofocus, at 56mm or more, I don't. I guess I should count myself lucky I get any autofocus at all. The manual for my D3200 specifies that autofocus requires a largest effective aperture of at least ƒ/5.6. The extension tubes are only really useful with the lens zoomed in to 55mm, at which ƒ/5.6 is the largest effective aperture of the lens by itself, and surely adding any extension tubes must have the effect of reducing the effective aperture somewhat; so when I am using my extension tubes, and getting autofocus, then at that point, I have my camera performing beyond the limits that Nikon claims for it. [/QUOTE]

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