Gundlach 8, 18, 24" Triple Convertible

hi all-

 

i was wondering on this type of lens and the other "convertible" lens, does it require the full say 18" draw

to focus the lens to infinity?

 

my camera has a little of 14" of bellows and I am looking for a long lens (4x5 format).

 

thanks in advance!

 

-david

A "converted" convertible requires MORE draw than the focal length. About 20" for the 18" element.

Hi David,

for a converter, you need just the extension, the focal length requires. i.e. extension is equal to fl for infinity.

Whereas the main point of the converted lens is not necessarily within the aperture plane/identical to the "unconverted" plane Ole might be right with his assumption of 20" for the 18". it's not generally more for the converted lens, but depends if the rear or front element is used.

What you are looking for is a telephoto lens, which has the main point far in front of the lens, hence the flange/focus distance is very much shorter then the focal length. Note, that extension for closer distances is increased again as with the normal lens of the same fl, so minimum distance might be long.

Regards,

Martin

thanks!

:-)