There are various reasons given, of various degrees of believeability: to reduce chromatic aberration, and to 'cut through haze or fog'. An old binocular can have discolored cement. Personally I find the effect very unpleasant. --Peter
From: "rhanna@___a" <rhanna@___a>
I came across a copy of the "Directory & Handbook of the Scientific Instrument Manufacturers Association (of Great Britain Ltd.)" ("SIMA") for 1952 which to quote the inside cover contains, "biographical information on the Association and the industry (and ) a useful index, giving the sources of 2,500 instruments manufactured by a hundred firms... The Association was established in 1916 as The British Optical Instrument Manufacturers Association. This volume is old enough to contain much information on firms of pre-war fame, as well as some of the 'newer' ones. For those interested in British optics it might be a title worth looking for. Regards, Robert.
Subject: 'Pushing binoculars'
From: "Osborn Optical" <optical-repair@___t>
> Re. Earl Osborne's observation about 'pushing' . . . In Britain, at least, it's not a new expression....
My "pushing" response was tongue-in-cheek. Having lived in the U.K. for a while, I was aware of usage there, and I was just having fun with Gordon, whom I have know for several years. Remember folks, optics is "light" work :) Earl
Subject: Diopter settings
After carrying out a mini survey amongst friends and fellow binocular enthusiasts I have found that I am far from unique in having discovered various discrepencies with binocular diopter settings of all kinds and qualities .
I am not a collector but do own and use eight different binoculars of varying quality and have noticed that the diopter adjustments I need to make vary considerably from model to model from minus 0.5 right out to minus 5 .
I am overdue an eye test but almost 3 years ago I had 20/20 vision in both eyes.
I also know of others with 20/20 vision in both eyes who have to make similar adjustments with an even wider variety of centre -focus binoculars and in one case with Fujinon individual eyepieces .
I would have thought this equated to a midpoint 0 position being perfect focus .
Although far from being an optics repair person I have taken enough binos apart to realise that the degree of incrementation required for such adjustments is very fine and totally dependent on the location and security of the travelling ocular unit , and can understand how easily inexpensive "disposable" varities given away free with 50 gallons of fuel or whatever could easily be thrown together with such negligence to detail but am surprised that even products as expensive as Zeiss , Swarovski and Nikon all seem to share this anomoly .
I wondered if others within the group had similar experiences and if perhaps one or two could explain what is happening here ?
I can't explain it but I can acknowledge it; many or most of the binoculars I acquire used have 'randomized' individual focus, where the diopter settings are not meaningful - the eyepiece