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Macro Alternatives

I tested the following two lenses:

Pentax D-FA 100mm 2.8 Macro digitally optimized, full-frame lens
Tamron 90mm 2.8 DI Macro digitally optimized, full-frame lens

Pentax and Tamron set at infinity. Note that the hood attaches to the rigid lens body on the Pentax and on the extending part on the Tamron.

Both lenses set at 1:1 macro reproduction ratio.

You can see how differently far the front elements are recessed. This means that the effective focus distance on the Pentax is 13cm while on the Tamron it is only 9.5cm. OTOH, this means that the Tamron has even less need for a hood because the front element is shielded even without.

I chose this rather bad page design (horizontal&vertical scrolling) because I believe it makes comparing easier. I omitted the full-frame resize, because vignetting or distortion was not detectable with my limited resources.

Lens	Centre	upper left corner	upper right corner	lower right corner	lower left corner
Pentax @ 2.8
Tamron @ 2.8

Lens	Centre	upper left corner	upper right corner	lower right corner	lower left corner
Pentax @ 8
Tamron @ 8

Lens	Centre	upper left corner	upper right corner	lower right corner	lower left corner
Pentax @ 16
Tamron @ 16

Lens	Centre	upper left corner	upper right corner	lower right corner	lower left corner
Pentax @ 32
Tamron @ 32

Conclusion:
I focused them manually and chose the best one of each setup. Here are some more "real-life" setups.

Tamron wide open:

Pentax wide open, sorry, focus is about 1mm different

Tamron f/11 open:

Pentax f/11 open

Bokeh wide open, Tamron:

Bokeh wide open, Pentax:

I found both lenses to be almost exactly the same. Yes, I know, the Tamron has tested better for sharpness, but I couldn't see this. I returned the Tamron, because I already have used the Pentax and could not return it. Also, the Pentax is smaller and a larger effective focus distance. I also am under the impression that Pentax's SMC coating is more effective against lens flare (not shown here). The Tamron is cheaper and better built. Both are great choices.

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