Canon 60mm f2.8 macro vs 85mm f1.8 + extension tube

I've played with the 85mm f1.8 + extension tubes (BTW, the very cheap ones are no good, you need the extension tubes to pass through the electrical contacts otherwise you can't easily change the aperture of the lens). It's OK in a pinch, but not close to the quality you'll get from a proper macro lens like the 60mm f2.8 USM.

Some sample galleries here :
http://www.pbase.com/cjed/ex85mmmacros

However, even with a full set of extension tubes (65mm) you don't quite get 1:1 magnification (approx a magnification of 0.875 or 1:1.14). The EF 85mm f1.8 also shows severe CA on specular highlights - see the jewelry photos in the gallery and similar shots from a Tamron macro lens in a sub-gallery on the second page.

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Check out my galleries (lots of macros) at :
http://www.pbase.com/cjed