I
understand the math. It is the practical experience that eludes me. Why in
actuality and testing I have done does it appear to be a 21" instead of a 71/2"?
The actual physical focusing plane using ground glass and cardboard boxes,
occurs at 533 mm instead of the 190 mm. If I remove the back piece, the lens is
correct at 190. Does any body have any idea why the black piece is on this lens
and what it is there for?
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]On Behalf Of DONALD MILLER
Sent: Saturday, March 29, 2003 9:27 AM
To: [EMAIL PROTECTED]
Subject: Re: [Cameramakers] Lens confusionThe inch determination (7 1/2) is the focal length of the lens. Therefore this lens would be 190 mm. This lens would require appr. 190 mm of bellows extension from the nodal point of the lens to the ground glass. The focusing is accomplished by extending the bellows further for nearer then infinity objects.
Main <[EMAIL PROTECTED]> wrote:
I am confused. My lens (thanks for the help so far) is Listed as an ILEX
Paragon anastigmat f:4.5, 7 1/2 inch. Meaning it focuses at 7.5 inches or
190 mm? Why during all my tests so far does it actually focus out at 21
inches or 533 mm?
I need to check this possible answer: The back of the lens has a black
anodized screw in section. Could this section be changing the focal length,
and is it in the correct place or should it be after the shutter, not on the
back of the lens?
