I have a 100/4 macro lens for my 67 II , BTW beautiful piece if glass, and would like to use it with rear converter. Does anybody know if it is possible, I did not find any information about it.

-- Pavel Medek (talema@top.cz), June 03, 1999

Answers

Pavel, I can't think of any optical reasons why you could not use a conveter on this lens. What these devices do is act like the rear component of a telephoto. SR

-- Steve Rasmussen (srasmuss@flash.net), July 19, 1999.

Pavel, I looked at the optical cross section of the 100 macro and would guess that it cannot be used with the 1.4x converter. The main lens is a Double Gauss type, just like the 105 f/2.4. This is not a good sign when it comes to fitting with the converter. The rear element is probably located as far rearward as possible to avoid having to use a retrofocus design. I cannot give an exact answer on this due to not being able to see the lens. BTW, this is the strangest macro design I've seen. It has a Cooke triplet as the lifesize attachment followed by the Double Gauss in the rear. SR

-- Steve Rasmussen (srasmuss@flash.net), July 21, 1999.

Joachim: In fact I used the German site to find the optical cross section of the 100mm. An excellent site but my reading of German is not so good. Ich sprechen nicht ser gut Deutsch. SR

-- Steve Rasmussen (srasmuss@flash.net), July 22, 1999.

Steve,

but I know that 100/2.4 is not possible to use with 1.4 converter, because rear group of the lens would touch the converter. Pentax specification says that this converter (1.4x) is recommended for lenses 200mm and more. So I am wonder if this true for new 100/4 macro also.

Pavel

-- Pavel Medek (talema@top.cz), July 20, 1999.

Pentax Germany has an excellent web page form which you can download PDF files containing very detailed technical specification on each 67 lens. These files list all available accessories for each lens, e.g. converters. Rear converters are not mentioned on the data sheet for the 100mm macro lens which should imply that you can not use them without problems.

-- Joachim Inkmann (Joachim.Inkmann@uni-konstanz.de), July 21, 1999.