What does HH on a lens mean

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austrokiwi1
Posts: 350
Joined: Sun Sep 14, 2014 10:53 am

What does HH on a lens mean

Post by austrokiwi1 »

I suspect this is a very basic question and that i am having a Homer Simpson moment!
I have a 105mm Process lens ( Staeble-Magnogon R) that has a green sticker on it. the sticker includes the lenses serial number its true focal length (103.9mm) and a box labeled "HH" with the value -0.5. Given the purpose of the lens I suspect HH might relate to distortion. Can any one enlighten me?

If it is distortion is -.5 good or bad?
Still learning,
Cameras' Sony A7rII, OLympus OMD-EM10II
Macro lenses: Printing nikkor 105mm, Sony FE 90mm F2.8 Macro G, Schneider Kreuznach Makro Iris 50mm , 2.8, Schnieder Kreuznach APO Componon HM 40mm F2.8 , Mamiya 645 120mm F4 Macro ( used with mirex tilt shift adapter), Olympus 135mm 4.5 bellows lens, Oly 80mm bellows lens, Olympus 60mm F2.8

steveminchington
Posts: 215
Joined: Sun Jul 22, 2012 2:30 pm
Location: Bedford UK

Post by steveminchington »

Hi,
Assuming this is the lens you have (I found it on eBay so it may be the very one) there is one little clue that you didn't mention in your post, and that is the apostrophe after the second H like this H'

Image
On a typical ray diagram the letters labeling rays entering a lens are just the letter and the label on rays exiting the lens are the letter with an apostrophe. So if you look at the ray diagram below, HH' is the ratio of the height of the object to the height of the image, or reproduction ratio.

This is a complete guess, but I would say that the -0.5 is a correction factor to the reproduction ratio which woudn't really matter normally but as this lens is a repro lens and would have been fitted on a copy camera, the reproduction ratio is important so the operator would have taken that into account when trying to achieve an exact size from an original. Since the focal length is marked as being slightly less than the nominal 105mm, I would say that it follows that the reproduction ratio would also be slightly less than it's nominal value.
Image

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