Macro Alternatives

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I tested the following two lenses:
  • Pentax D-FA 100mm 2.8 Macro digitally optimized, full-frame lens
  • Pentax A 50mm 1.4 + Vivitar 2x Macro Focusing Teleconverter full-frame, converter based

Both lenses set at infinity, the Vivitar Combo (right) is slightly shorter than the Pentax (left).

Both lenses set at their maximum magnification (~1:1) - the Vivitar Combo is quite a bit shorter.

The Vivitar is basically a multicoated 7-element Teleconverter that enables extension like in an extension tube. This makes it possible to focus to 1:1 with a 50mm lens attached. Of course, due to the laws of optics, the resulting lens will be a 50mm*2=100mm lens with f/(1.4*2)=f/2.8 as it brightest aperture - so basically exactly what the Pentax is.

Going on a trip, what will you take? A single Macro lens or a great, sharp 50mm with a Macro Focusing Teleconverter? The latter combo is smaller, cheaper and more versatile. I've used the Vivitar Macro Focusing Teleconverter quite a lot, coupled to my Macro, as can be seen in my gallery. I have also used macro converters for standard lenses prior to that: here and here, two converters stacked.
The question what to take has been bothering me for "ages". Ron on the dpreview forum did a comparison which showed the Vivitar to be quite nice. But I needed to do some testing myself, with my specimens. So here we go.
The first thing I noticed is that the Vivitar is 1:1 only when you set the 50mm lens to its nearest focus position. I also had to reposition the camera with regard to the subject. The effective minimal focus position (front element to subject) is 120mm for the Vivitar and 130mm for the Pentax. I did not test the lenses for curvature of field. It is pretty clear that the Macro will be much better here. But one has to ask oneself, whether a curved field is a problem in rel-life. If you are photographing stamps: Yes. If you are photographing plants and bugs: Not really. The curvature of field seems to be noticeable in the viewfinder with the Vivitar combo, but this could be my imagination running wild. ;)

Don't use this lens wide open for macro! While the Bokeh is creamy smooth, there's lots of chromatic aberrations and the straight ruler appears to be severely distorted!

ISO 200, RAW+RSE and a bounced Metz 32MZ-3, equivalent f-stop f/11 for both
Pentax Vivitar
I find the results of the Vivitar really impressive! It's not quite as sharp and lacks a bit of contrast, but otherwise it presents a great way to explore the world of macro in a compact and versatile package. If you'd like Vivitar to reissue this converter, maybe even in a "digital" version, drop them an email:

And now, some testshots with differing effective apertures between the two lenses.

f/13, ISO 200, RAW+RSE and a bounced Metz 32MZ-3 for both
(equivalent to f/26 on the Vivitar-Combo!)
Pentax Vivitar
Well, the Vivitar puts on an impressive show, but stands no chance against the DFA Macro. But at f/26 (the effective f/stop of the Vivitar Combo) we have to expect diffraction. Lesson: Watch your f-stop!

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