NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/rec/photo/20180

Internet Message Format | 1992-11-19 | 3.1 KB

Path: sparky!uunet!zaphod.mps.ohio-state.edu!sdd.hp.com!nobody
From: [e-mail] (John Ongtooguk)
Newsgroups: rec.photo
Subject: Re: Resolution of Lens ???
Date: 20 Nov 1992 02:08:39 GMT
Organization: Hewlett-Packard, San Diego Division
Lines: 45
Distribution: na
Message-ID: <[e-mail]>
References: <[e-mail]> <[e-mail]> <[e-mail]> <[e-mail]>
NNTP-Posting-Host: hpsdlg10.sdd.hp.com

In article <[e-mail]>, [e-mail] (robert.m.atkins) writes:
|> In article <[e-mail]>, [e-mail] (Steve Gombosi) writes:
|> >......
|> > Maybe I don't understand how this all works, but aren't the resolutions
|> > of the lens, film, and system (lens *and* film) related in this way:
|> >
|> >     1/Rs = 1/Rl + 1/Rf

     From one of the Kodak publications (B&W films ?) I recall that it's
     something like 1/film^ + 1/lens^2 = 1/image^2 ; I think it's correct
     as you're supposed to get about 70 lp/mm from a film/lens at 100 lp/mm.

|>                        ............ yet modern photography had GREAT
|> trouble with the best lenses available. If you look at most of their
|> tests lenses tended to top out at about only 70 lp/mm..

   In Outdoor Photo. George Lepp mentioned that the highest numbers
   that he found on Tech Pan were about 120 lp/mm to 130 lp/mm from
   the tests on the Nikon and Canon 55mm and 50mm macros. He also
   found that Modern Photo's numbers were kind of low. I've worn
   out one of Modern's buying guides trying to make sense of some
   of tests and I found that there wasn't too much correlation between
   the numbers and what I thought was the best indicator of lens
   quality; 'well defined detail'. Their qualitative ratings were
   otherwise confusing as an excellent zoom might be an almost average
   normal lens. The highest numbers in the buying guide that I recall
   were from the Nikon 35mm f1.4 at about 87 lp/mm, although in one
   of their last issues I think that they stated that some of the
   90mm to 105mm macros tested around 100 lp/mm.

|> A couple of other points come to mind. (1) At the resolution limit the
|> image of the test target is no longer high contrast (the aerial image
|> that is). The resolving power of Tech Pan is only 125 lp/mm for low
|> contrast targets (usually 1:1.6?). Thus as you approach the resolving
|> limit of the lens, the resolving power of the film itself drops also.
|> Thus if the lens JUST resolved 400 lp/mm in a low contrast aerial
|> image, 125 lp/mm from the film would give only 95lp/mm on the negative.

   Good point. I recall an ad (with no data to back it up) that stated
   that the resolution of the new Leica 105mm apo-macro exceeded the
   resolving power of Tech Pan. It or the Nikon 105 apo process lens
   might be the tools you need to test your theory as you should be
   able to record a high value that drops off quickly as you stop down.

   John Ongtooguk ([e-mail])