[Kodachrome 25]

Another option are loupe macro lenses with microscope lens thread, which are built for the magnification range you mentioned and which are also available in rather short focal lengths 12.5-50 mm. I'd say these are no apochromats though. At least I would guess that from the absence of the "Apo" tag in the lens designations. I know that microscope lens manufacturers (Leitz, Zeiss, Olympus, Wild) never fail to emphasize that a lens has that type of aberration correction. I have no idea about the optical performance of this lens type.



[url="http://de.wikipedia.org/wiki/Lupenobjektiv"]http://de.wikipedia.org/wiki/Lupenobjektiv[/url]

[url="http://www.macrolenses.de/start.php?lang=en"]http://www.macrolenses.de/start.php?lang=en[/url] via [url="http://de.wikipedia.org/wiki/RMS-Gewinde"]http://de.wikipedia.org/wiki/RMS-Gewinde[/url]



[url="http://www.ebay.de/itm/RMS-Thread-to-M42-Adapter-for-Zeiss-Luminar-Bellows-/140718400195?pt=LH_DefaultDomain_0&hash=item20c37862c3#ht_890wt_957"]RMS to M42x1 adapter[/url]

[url="http://www.ebay.de/itm/Photar-1-2-5-25-Leitz-Wetzlar-Balgengerat-Kilfitt-Naba-/170803115669?pt=DE_Foto_Camcorder_Objektive&hash=item27c4a8b695#ht_500wt_972"]Leitz Photar 25/2.5[/url]

[url="http://www.ebay.de/itm/Leitz-Photar-1-2-5-25-/160761980853?pt=LH_DefaultDomain_77&hash=item256e2927b5#ht_601wt_1132"]Leitz Photar 25/2.5[/url]

[url="http://www.ebay.de/itm/Canon-Lupenobjektiv-3-5-20mm-/180833151081?pt=DE_Foto_Camcorder_Objektive&hash=item2a1a7ee869#ht_500wt_738"]Canon 20/3.5[/url]