{"id":5121,"date":"2015-12-12T00:00:00","date_gmt":"2015-12-12T00:00:00","guid":{"rendered":"https:\/\/blog.tractoptics.com\/https-swiftotterincubator-wpcomstaging-com-videosview-what-do-the-numbers-mean\/"},"modified":"2026-05-21T11:38:45","modified_gmt":"2026-05-21T11:38:45","slug":"what-do-the-numbers-mean","status":"publish","type":"post","link":"https:\/\/blog.tract-optics.co.za\/what-do-the-numbers-mean\/","title":{"rendered":"What Do The Numbers Mean"},"content":{"rendered":"<div style=\"position: relative;padding-top: 56.25%\"><iframe style=\"border: 0;position: absolute;top: 0;height: 100%;width: 100%\" src=\"https:\/\/iframe.mediadelivery.net\/embed\/330784\/27150aac-0de8-422a-88ff-3fa08e958894?autoplay=false&#038;loop=false&#038;muted=false&#038;preload=true&#038;responsive=true\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/div><p>Whether you&#8217;re scanning timber for that trophy buck or glassing distant targets at the range, the numbers on your binoculars aren&#8217;t just marketing specs\u2014they&#8217;re the key to unlocking performance when it matters most.<\/p><p>When you see &#8220;10&#215;42&#8221; stamped on <a href=\"https:\/\/blog.tract-optics.co.za\/how-to-glass-effectively-western-hunting\/\">TRACT binoculars<\/a>, those numbers tell a story about low-light capability, field of view, and how well you&#8217;ll perform during those critical dawn and dusk moments. Let&#8217;s break down what these numbers actually mean and why understanding them will make you a better hunter and shooter.<\/p><div id=\"ez-toc-container\" class=\"ez-toc-v2_0_83 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\"><div class=\"ez-toc-title-container\"><p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p><span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div><nav><ul class='ez-toc-list ez-toc-list-level-1 eztoc-toggle-hide-by-default' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/blog.tract-optics.co.za\/what-do-the-numbers-mean\/#Understanding_Exit_Pupil_The_Secret_to_Low-Light_Performance\" >Understanding Exit Pupil: The Secret to Low-Light Performance<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/blog.tract-optics.co.za\/what-do-the-numbers-mean\/#Magnification_vs_Light_Gathering_Finding_Your_Sweet_Spot\" >Magnification vs. Light Gathering: Finding Your Sweet Spot<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/blog.tract-optics.co.za\/what-do-the-numbers-mean\/#Key_Features_That_Make_Numbers_Matter\" >Key Features That Make Numbers Matter<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/blog.tract-optics.co.za\/what-do-the-numbers-mean\/#Real-World_Applications_When_Exit_Pupil_Saves_Your_Hunt\" >Real-World Applications: When Exit Pupil Saves Your Hunt<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/blog.tract-optics.co.za\/what-do-the-numbers-mean\/#Comparing_Configuration_Options\" >Comparing Configuration Options<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/blog.tract-optics.co.za\/what-do-the-numbers-mean\/#Final_Thought\" >Final Thought<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/blog.tract-optics.co.za\/what-do-the-numbers-mean\/#Frequently_Asked_Questions\" >Frequently Asked Questions<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/blog.tract-optics.co.za\/what-do-the-numbers-mean\/#What_does_10x42_mean_on_binoculars\" >What does 10x42 mean on binoculars?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/blog.tract-optics.co.za\/what-do-the-numbers-mean\/#How_do_you_calculate_exit_pupil_on_binoculars\" >How do you calculate exit pupil on binoculars?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/blog.tract-optics.co.za\/what-do-the-numbers-mean\/#What_is_the_best_exit_pupil_size_for_hunting\" >What is the best exit pupil size for hunting?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/blog.tract-optics.co.za\/what-do-the-numbers-mean\/#Why_is_exit_pupil_important_in_binoculars\" >Why is exit pupil important in binoculars?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/blog.tract-optics.co.za\/what-do-the-numbers-mean\/#Should_I_choose_8x42_or_10x42_binoculars_for_hunting\" >Should I choose 8x42 or 10x42 binoculars for hunting?<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div><h2><span class=\"ez-toc-section\" id=\"Understanding_Exit_Pupil_The_Secret_to_Low-Light_Performance\"><\/span>Understanding Exit Pupil: The Secret to Low-Light Performance<span class=\"ez-toc-section-end\"><\/span><\/h2><p>Here&#8217;s the truth: exit pupil is the most overlooked specification that directly impacts your success in the field. Your eye&#8217;s pupil naturally dilates from 2 millimeters in bright sunlight up to 7 millimeters in total darkness. But here&#8217;s what matters most\u2014in those critical low-light situations when game is most active, your pupil dilates to between 4 and 5 millimeters.<\/p><p>The exit pupil calculation is simple: divide the objective lens diameter by the magnification. For a 10&#215;42 <a href=\"https:\/\/blog.tract-optics.co.za\/best-rifle-calibers-for-bear-hunting\/\">binocular<\/a>, that&#8217;s 42 \u00f7 10 = 4.2 millimeters. This 4.2mm exit pupil perfectly matches your eye&#8217;s natural dilation during prime <a href=\"https:\/\/blog.tract-optics.co.za\/rifle-marksmanship-trigger-control-success\/\">hunting<\/a> hours, giving you maximum light transmission when you need it most.<\/p><p><strong>PRO TIP:<\/strong> If you&#8217;re primarily hunting in heavily wooded areas or low-light conditions, consider an 8&#215;42 configuration. The larger 5.25mm exit pupil (42 \u00f7 8) provides even better <a href=\"https:\/\/blog.tract-optics.co.za\/history-of-hunting-binoculars\/\">low-light performance<\/a>, though you&#8217;ll sacrifice some magnification.<\/p><h2><span class=\"ez-toc-section\" id=\"Magnification_vs_Light_Gathering_Finding_Your_Sweet_Spot\"><\/span>Magnification vs. Light Gathering: Finding Your Sweet Spot<span class=\"ez-toc-section-end\"><\/span><\/h2><p>When you&#8217;re choosing between different magnification levels, you&#8217;re making a trade-off between reach and light-gathering ability. Higher magnification doesn&#8217;t always mean better performance\u2014it depends entirely on your hunting style and conditions.<\/p><p>For whitetail hunters working timber edges at dawn, an 8&#215;42 binocular often outperforms a 10&#215;42 simply because that larger exit pupil pulls in more usable light. But if you&#8217;re hunting open country where you need to identify animals at extreme distances, the extra magnification of a 10&#215;42 becomes invaluable.<\/p><p>Notice something? TRACT&#8217;s <a href=\"https:\/\/blog.tract-optics.co.za\/right-binocular-or-binocular-rangefinder\/\">TORIC binoculars<\/a> are available in both 8&#215;42 and 10&#215;42 configurations specifically because different hunting scenarios demand different optical approaches.<\/p><h2><span class=\"ez-toc-section\" id=\"Key_Features_That_Make_Numbers_Matter\"><\/span>Key Features That Make Numbers Matter<span class=\"ez-toc-section-end\"><\/span><\/h2><p>The exit pupil calculation only tells part of the story. Here&#8217;s what separates premium optics from budget alternatives:<\/p><ul><li><strong>SCHOTT HT Glass:<\/strong> Premium German glass maximizes light transmission across the entire exit pupil<\/li><li><strong>Phase-Corrected Prisms:<\/strong> Ensure all that gathered light reaches your eye with maximum clarity<\/li><li><strong>Multi-Layer Coatings:<\/strong> Reduce reflective loss, making every photon count in low light<\/li><li><strong>Precise Mechanical Design:<\/strong> Maintains exit pupil alignment even under field conditions<\/li><\/ul><p>That&#8217;s because the best exit pupil in the world means nothing if the optical system can&#8217;t efficiently deliver that light to your eye.<\/p><h2><span class=\"ez-toc-section\" id=\"Real-World_Applications_When_Exit_Pupil_Saves_Your_Hunt\"><\/span>Real-World Applications: When Exit Pupil Saves Your Hunt<span class=\"ez-toc-section-end\"><\/span><\/h2><p>Let&#8217;s talk about practical scenarios where understanding exit pupil makes the difference between success and going home empty-handed:<\/p><p><strong>Early Season Bow Hunting:<\/strong> You&#8217;re in your stand 30 minutes before legal shooting light. That 4.2mm exit pupil on your 10&#215;42 binoculars is pulling in maximum available light, letting you identify deer movement while competitors with inadequate exit pupils are still squinting into shadows.<\/p><p><strong>Late-Season Rifle Hunting:<\/strong> It&#8217;s last light, and you spot movement 400 yards across a cut cornfield. Your properly matched exit pupil gives you the light-gathering power to positively identify your target and assess shot placement opportunities.<\/p><p><strong>Competition Shooting:<\/strong> During early morning matches or under overcast conditions, that perfectly calculated exit pupil helps you spot bullet holes and read wind indicators that others might miss.<\/p><h2><span class=\"ez-toc-section\" id=\"Comparing_Configuration_Options\"><\/span>Comparing Configuration Options<span class=\"ez-toc-section-end\"><\/span><\/h2><p>Here&#8217;s how different binocular configurations stack up for exit pupil performance:<\/p><ul><li><strong>8&#215;32:<\/strong> 4.0mm exit pupil &#8211; Compact, good for daylight use<\/li><li><strong>8&#215;42:<\/strong> 5.25mm exit pupil &#8211; Excellent low-light performance, slightly bulkier<\/li><li><strong>10&#215;32:<\/strong> 3.2mm exit pupil &#8211; Limited low-light capability<\/li><li><strong>10&#215;42:<\/strong> 4.2mm exit pupil &#8211; Best balance of magnification and low-light performance<\/li><li><strong>10&#215;50:<\/strong> 5.0mm exit pupil &#8211; Maximum light gathering, but significantly heavier<\/li><\/ul><p>For most hunters and competitive shooters, the 10&#215;42 configuration hits the sweet spot\u2014enough magnification for detailed observation with an exit pupil that matches your eye&#8217;s performance during critical low-light periods.<\/p><h2><span class=\"ez-toc-section\" id=\"Final_Thought\"><\/span>Final Thought<span class=\"ez-toc-section-end\"><\/span><\/h2><p>Understanding exit pupil isn&#8217;t about memorizing formulas\u2014it&#8217;s about making informed decisions that directly impact your performance in the field. When you match your binocular&#8217;s exit pupil to your hunting conditions and shooting scenarios, you&#8217;re not just buying better optics, you&#8217;re investing in those crucial moments when light is fading and opportunities are fleeting. The right exit pupil calculation can mean the difference between a successful hunt and a story about the one that got away.<\/p><h2><span class=\"ez-toc-section\" id=\"Frequently_Asked_Questions\"><\/span>Frequently Asked Questions<span class=\"ez-toc-section-end\"><\/span><\/h2><h3>What does 10&#215;42 mean on binoculars?<\/h3><p>The first number (10) is the magnification power, meaning objects appear 10 times closer. The second number (42) is the objective lens diameter in millimeters. Together, they determine the exit pupil: 42 \u00f7 10 = 4.2mm, which affects low-light performance.<\/p><h3><span class=\"ez-toc-section\" id=\"How_do_you_calculate_exit_pupil_on_binoculars\"><\/span>How do you calculate exit pupil on binoculars?<span class=\"ez-toc-section-end\"><\/span><\/h3><p>Divide the objective lens diameter by the magnification. For example, a 10&#215;42 binocular has an exit pupil of 4.2mm (42 \u00f7 10). This number determines how much light reaches your eye and affects low-light viewing performance.<\/p><h3><span class=\"ez-toc-section\" id=\"What_is_the_best_exit_pupil_size_for_hunting\"><\/span>What is the best exit pupil size for hunting?<span class=\"ez-toc-section-end\"><\/span><\/h3><p>For hunting, an exit pupil between 4-5mm is ideal because it matches your eye&#8217;s natural dilation during dawn and dusk when game is most active. This is why 8&#215;42 (5.25mm) and 10&#215;42 (4.2mm) binoculars are popular hunting choices.<\/p><h3><span class=\"ez-toc-section\" id=\"Why_is_exit_pupil_important_in_binoculars\"><\/span>Why is exit pupil important in binoculars?<span class=\"ez-toc-section-end\"><\/span><\/h3><p>Exit pupil determines how much light reaches your eye. Your pupil dilates from 2mm in bright light to 7mm in darkness. During critical hunting hours, your pupil is 4-5mm, so matching this with your binocular&#8217;s exit pupil maximizes light transmission and image brightness.<\/p><h3>Should I choose 8&#215;42 or 10&#215;42 binoculars for hunting?<\/h3><p>8&#215;42 offers better low-light performance with a 5.25mm exit pupil, making it ideal for wooded areas and dawn\/dusk hunting. 10&#215;42 provides more magnification with good low-light capability (4.2mm exit pupil), better for open country and longer-range observation.<\/p><p>{  &#8220;@context&#8221;: &#8220;https:\/\/schema.org&#8221;,  &#8220;@type&#8221;: &#8220;FAQPage&#8221;,  &#8220;mainEntity&#8221;: [    {      &#8220;@type&#8221;: &#8220;Question&#8221;,      &#8220;name&#8221;: &#8220;What does 10&#215;42 mean on binoculars?&#8221;,      &#8220;acceptedAnswer&#8221;: {        &#8220;@type&#8221;: &#8220;Answer&#8221;,        &#8220;text&#8221;: &#8220;The first number (10) is the magnification power, meaning objects appear 10 times closer. The second number (42) is the objective lens diameter in millimeters. Together, they determine the exit pupil: 42 u00f7 10 = 4.2mm, which affects low-light performance.&#8221;      }    },    {      &#8220;@type&#8221;: &#8220;Question&#8221;,      &#8220;name&#8221;: &#8220;How do you calculate exit pupil on binoculars?&#8221;,      &#8220;acceptedAnswer&#8221;: {        &#8220;@type&#8221;: &#8220;Answer&#8221;,        &#8220;text&#8221;: &#8220;Divide the objective lens diameter by the magnification. For example, a 10&#215;42 binocular has an exit pupil of 4.2mm (42 u00f7 10). This number determines how much light reaches your eye and affects low-light viewing performance.&#8221;      }    },    {      &#8220;@type&#8221;: &#8220;Question&#8221;,      &#8220;name&#8221;: &#8220;What is the best exit pupil size for hunting?&#8221;,      &#8220;acceptedAnswer&#8221;: {        &#8220;@type&#8221;: &#8220;Answer&#8221;,        &#8220;text&#8221;: &#8220;For hunting, an exit pupil between 4-5mm is ideal because it matches your eye&#8217;s natural dilation during dawn and dusk when game is most active. This is why 8&#215;42 (5.25mm) and 10&#215;42 (4.2mm) binoculars are popular hunting choices.&#8221;      }    },    {      &#8220;@type&#8221;: &#8220;Question&#8221;,      &#8220;name&#8221;: &#8220;Why is exit pupil important in binoculars?&#8221;,      &#8220;acceptedAnswer&#8221;: {        &#8220;@type&#8221;: &#8220;Answer&#8221;,        &#8220;text&#8221;: &#8220;Exit pupil determines how much light reaches your eye. Your pupil dilates from 2mm in bright light to 7mm in darkness. During critical hunting hours, your pupil is 4-5mm, so matching this with your binocular&#8217;s exit pupil maximizes light transmission and image brightness.&#8221;      }    },    {      &#8220;@type&#8221;: &#8220;Question&#8221;,      &#8220;name&#8221;: &#8220;Should I choose 8&#215;42 or 10&#215;42 binoculars for hunting?&#8221;,      &#8220;acceptedAnswer&#8221;: {        &#8220;@type&#8221;: &#8220;Answer&#8221;,        &#8220;text&#8221;: &#8220;8&#215;42 offers better low-light performance with a 5.25mm exit pupil, making it ideal for wooded areas and dawn\/dusk hunting. 10&#215;42 provides more magnification with good low-light capability (4.2mm exit pupil), better for open country and longer-range observation.&#8221;      }    }  ]}<\/p><p><strong>Let&#8217;s make every shot count.<\/strong><\/p><p>Have questions? We&#8217;re here to help:<\/p><ul><li>\ud83d\udcde Call: <a href=\"tel:631-662-7354\">631-662-7354<\/a><\/li><li>\ud83d\udce7 Email: <a href=\"mailto:support@tractoptics.com\">support@tractoptics.com<\/a><\/li><li>\ud83d\udcac Live Chat available on <a href=\"https:\/\/tractoptics.com\" target=\"_blank\" rel=\"noopener\">tractoptics.com<\/a><\/li><\/ul><p><a href=\"https:\/\/www.trustpilot.com\/review\/tractoptics.com\" target=\"_blank\" rel=\"noopener\">\u2b50 See what our customers say on Trustpilot<\/a><\/p>","protected":false},"excerpt":{"rendered":"<p>Understanding binocular numbers like 10&#215;42 isn&#8217;t just about specs\u2014it&#8217;s about calculating exit pupil for maximum low-light performance. Learn how these numbers directly impact your hunting and shooting success.<\/p>\n","protected":false},"author":2,"featured_media":12637,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2252,2256,2274],"tags":[4438,4444,4445,2797,4446,2899,3004,3032,3047,3048,3049,3050,3053,3054,3056,3057,3058,3060,3064,3074,3078,3079,3082,3085,3086,3087,3088,3089,3091,3092,3093,4447,3351],"class_list":["post-5121","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-binoculars","category-how-to","category-video","tag-10x42-vs-8x42-binoculars","tag-binocular-low-light-performance","tag-exit-pupil-hunting","tag-hunting","tag-hunting-binocular-specifications","tag-long-range-rifle-scope","tag-rifle","tag-rifle-scope","tag-rifle-scope-objective-size","tag-rifle-scope-reticle","tag-rifle-scope-reticles","tag-rifle-scope-reticles-explained","tag-rifle-scope-turret-knobs","tag-rifle-scope-turrets","tag-rifle-scope-windage-adjustment","tag-rifle-scope-with-ballistic-calculator","tag-rifle-scopes","tag-rifle-scopes-for-sale","tag-rifle-size-for-deer-hunting","tag-rifle-turret","tag-rifles-for-deer-hunting","tag-riflescope","tag-riflescopes","tag-rimfire-bdc-reticle","tag-rimfire-bdc-scope","tag-rimfire-optics","tag-rimfire-rifle-scope","tag-rimfire-rifle-scopes","tag-rimfire-scope","tag-rimfire-scope-3-9x40","tag-rimfire-scope-with-bdc","tag-what-do-binocular-numbers-mean","tag-wistia"],"_links":{"self":[{"href":"https:\/\/blog.tract-optics.co.za\/wp-json\/wp\/v2\/posts\/5121","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.tract-optics.co.za\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.tract-optics.co.za\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.tract-optics.co.za\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.tract-optics.co.za\/wp-json\/wp\/v2\/comments?post=5121"}],"version-history":[{"count":3,"href":"https:\/\/blog.tract-optics.co.za\/wp-json\/wp\/v2\/posts\/5121\/revisions"}],"predecessor-version":[{"id":12638,"href":"https:\/\/blog.tract-optics.co.za\/wp-json\/wp\/v2\/posts\/5121\/revisions\/12638"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blog.tract-optics.co.za\/wp-json\/wp\/v2\/media\/12637"}],"wp:attachment":[{"href":"https:\/\/blog.tract-optics.co.za\/wp-json\/wp\/v2\/media?parent=5121"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.tract-optics.co.za\/wp-json\/wp\/v2\/categories?post=5121"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.tract-optics.co.za\/wp-json\/wp\/v2\/tags?post=5121"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}