David Leung extension tubes

[TimB]

Re: the extension tubes review in this weeks AP on page 39, can anyone tell me if the 12mm tube is used with a Canon 50mm lens will it give lifesize magnification? I see there are 20mm & 36mm avail as well. Thanks.

[Benchista]

With the lens set to infinity focus, the extension required to give 1:1 magnification is equal to the focal lenght, i.e. you would need 50mm of extension. However, at the minimum focusing distance, there's additional extension within the lens itself - according to this thread elsewhere, 7.5mm. So you would need 42.5mm of extension to get 1:1.

[Norman]

The maths is quite complicated as different lenses will have different amounts of extension "built in" but 12mm of extension on a 50mm will give a magnification of about 0.4. To get 1.0 (lifesize) you'll need about 43mm of extension. i.e. 12 + 36 is close enough.

Edit: Too slow.

[daft_biker]

12mm of extension doesn't really do a lot on a 50mm (the right way round).

Does loads on my 24mm though...can focus really close to the front element and still get wideangle perspective on FF.