ASTM_F_1753_-_96_2014.pdf

Designation:F175396(Reapproved 2014)An American National StandardStandard Specification forClassification and Marking of Single-Lens Scopes for Usewith Archery Bows1This standard is issued under the fixed designation F1753;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This specification covers lenses and scopes used inconjunction with archery bows.It establishes a standardizedsystem for the classification of these lenses in terms of theiroptical magnification,the marking of the scopes in which thelenses are mounted,and charts depicting the empirical rela-tionship of the apparent magnification the consumer can expectto obtain when a correctly marked lens is used under specificconditions.1.2 AcuityThe visual acuity of these lenses is related tothe magnification of the lens in general.For the average subjectthere can be an improvement in acuity with lenses havingapparent magnifications of 2 to 4 and a decrement in acuitywith lenses of 6 and greater.1.2.1 Acuity also is dependent on other factors,such as thespecific individual,lens quality,and the size and quality of therear aperture(peep)used in conjunction with the lens.Beyondthis statement,acuity is not the subject of this specification.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.2.Terminology2.1 Definitions:2.1.1 apparent magnification,napparent increase in sizeof an object as viewed through the subject lens held at aspecific distance from the users eye.2.1.2 diopter,nreciprocal of the focal length of the lens asmeasured in metres.One diopter is the rating obtained whenthe constant 1 is divided by the focal length value of a lenshaving a 1-m focal length.2.1.3 eye-to-scope distance(ETS),ndistance the(scope)lens is placed from the individuals eye when in use.If theeye-to-scope distance is measured in metres,it is specified as(ESM)and no conversion factor is required in the apparentmagnification formula.When the eye-to-scope distance ismeasured in inches,it is designated as(ESI).To calculateapparent magnification,the metres-to-inches conversion factorof 39.37 appears in the equation.2.1.4 focal length,ndistance,measured in metres,fromthe center of the subject lens to the point where incident planelight waves passing through the lens are brought to the sharpestpossible focus.2.1.5 optical magnification,ncharacteristic of a particularlens defined as the reciprocal of the lens focal length asmeasured in metres and stated in diopters.2.1.6 peep sight,nrear sighting device placed in or ontothe bow string,having a small opening in it that the archerpeers through to view the lens or scope being used as a sightingdevice.The combination of the lens and rear peep sight used inthis manner mimics a primitive telescope.3.Classification3.1 Optical MagnificationThis is the magnifying power ofa lens as measured by the reciprocal of the focal length of thelens in metres.It is expressed as a practical unit in terms of afocal length equal to one metre(the unit diopter).The larger thediopter number,the greater the magnifying power of the lens.3.2 Apparent MagnificationThis is the apparent increasein object size one experiences when viewing the object throughone of these magnifying lenses.It is dependent on thefollowing two factors:3.2.1 The optical magnification of the scope lens as mea-sured in diopters,and3.2.2 The distance the scope is placed from the users eye.3.3 Apparent magnification is defined empirically by thefollowing relationship:Apparent magnification5 1/1 2 D 3ESM!(1)where:D=lens optical magnification,diopters,andESM=eye-to-scope distance,m.3.3.1 If the eye-to-scope distance is measured in inches(ESI),the relationship becomes:Apparent magnification5 1/1 2 D 3ESI/39.37!(2)1This specification is under the jurisdiction of ASTM Committee F08 on SportsEquipment,Playing Surfaces,and Facilities and is the direct responsibility ofSubcommittee F08.16 on Archery Products.Current edition approved Sept.1,2014.Published November 2014.Originallyapproved in 1996.Last previous edition approved in 2010 as F1753 96(2010).DOI:10.1520/F1753-96R14.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 where:ESI=eye-to-scope distance,in.,and39.37=metres-to-inches conversion factor.3.4 Fig.1 and Fig.2 are graphic representations of themagnification relationship.Individually,one might prefer onechart over the other.Both charts contain the same informationbut display that information in a different format.3.4.1 Given the optical magnification of a lens in dioptersand the distance it is to be placed from the users eye,one candetermine the apparent magnification,that is,2,3,4,etc.NOTE1Fig.3 and Fig.4 are si