100 f/4 with rear converter

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, 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,

 

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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.

 

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Pavel

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

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:

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