Macro Questions concerning AF extension tubes.

Vlad S wrote:

alfredo_tomato wrote:

It seems the big disadvantage of extension tubes is having to take the lens off to shoot other than Macro.

The most fundamental disadvantage is the inferior image quality with extension tubes compare to true macro lenses.

An ordinary lens on tubes surely doesn't work in the intended position. Wide open, sharpness gets miserable typically. However typically one shoots macro stopped-down a lot in order to get useful DoF, and the biggest issues tend to go away, to the point that the results are usually a bit better than with close-up diopters. One doesn't get the flat field and low distortion of dedicated macros, and mostly not the quite the same sharpness, but this may not matter that much when shooting real-life 3D stuff (unlike with resolution test targets, currency and stamps!). With 3D stuff, what matters a lot is the rendering of the out-of-focus areas. This depends a lot on a particular lens used, also with macros. Nervous background bokeh is highly undesirable, while nervous foreground bokeh mostly passes due to certain composition norms. Zooms may be rather inpredictable when used on extension tubes, "super-zooms" particularly.

Adjusting the magnification over a wide range just by turning the focus ring is a huge practical advantage of macro lenses. Close-up diopters are a bit less inconvenient than extension tubes (also TCs).