Click here if you are having trouble logging into the forums Cloudy Nights - Official Forums of the 2009 International Year of Astronomy Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu.... uh, User   You are not logged in. [Login] Entrance · Main Index · Search · New user · Who's Online FAQ · Calendar Equipment Discussions >> Binoculars Previous   Index   Next   Flat   EdZ Professor EdZ Reged: 02/15/02 Posts: 12514 Loc: Cumberland, R I , USA42N71.4W Affect of Eye Pupil on Binocular Aperture       07/22/04 11:38 AM Edit   Reply   Quote   Quick Reply:   Affect of Eye Pupil on Binocular Aperture THREAD A complete explanation of why you should take into consideration the maximum dilation of your own eye pupils before you consider what size binocular to purchase. This explains the implications of using a binocular with exit pupils that are larger than your eye pupils. In a nut shell, if you are using a binocular with a 7mm exit pupil, for example a 10x70, but your eyes dilate to only a maximum of 5mm, then your binocular is effectively performing as if it were 10x50. You gain no more light gathering, brightness or resolution than the maximum exit pupil allows. In this case the maximum exit pupil is controlled by your eyes and would be limited to 5mm. A collection of my various posts on this topic and predominantly modified and corrected to the information in the thread above led to publishing this article Affect of Eye Pupil on Binocular Aperture CN REPORT This information is just as relavant to a telescope user who is attempting to maximize brightness of image by using the largest possible exit pupil that the equipment on hand will allow. In the same manner as stated above, if the exit pupil exceeds the maximum dilated eye pupil, then you are reducing the effective aperture of the scope. A member asked "I think these are great binoculars...BUT... I find they amplify sky glow or produce it? ... Is this because of the rather large exit pupil(7.1mm)? I don't see this glow in my 15x70's and I'm guessing that it's because of the 4.4mm exit pupil or the higher magnification." Binocular newbie confusion about Exit Pupil This reply addresses both too large exit pupil, which can generate washed out images, and also too large eye pupil which can decrease effective aperture. edz Edited by EdZ (03/17/06 07:33 PM) Post Extras       Entire thread Subject Posted by Posted on "BEST OF" the Binocular Forum - Start Here EdZ 01/24/04 07:51 AM GOOD STUFF FOR BEGINNERS EdZ   01/26/07 01:48 PM First Binocular Purchase? Questions? EdZ   01/26/07 01:47 PM Binoviewer - Scope - Binocular Equivalents EdZ   01/26/07 01:46 PM Surface Brightness of Extended Objects EdZ   03/17/06 04:00 PM Polish Binocular Tests and Reviews EdZ   03/07/06 09:52 AM Writing a Binocular Review EdZ   10/29/05 12:29 PM Limiting Magnitude and NELM EdZ   10/29/05 12:28 PM Resolution Testing and USAF Res Charts EdZ   10/29/05 12:27 PM Chromatic Aberration, Triplets, Semi-Apo, Apo EdZ   10/29/05 11:41 AM Dark Adaptation, Eye Pupils, Lights EdZ   08/25/05 10:50 AM BOOKS for Binocular Observers EdZ   06/02/05 07:46 PM Binocular Deep Magnitude Observing Charts EdZ   05/03/05 07:45 PM Binocular Photo Gallery EdZ   03/28/05 11:05 AM Binocular Vision Summation - Two Eyes vs One Eye EdZ   02/10/05 11:53 AM POLLS in Binocular Forum - take a poll EdZ   02/10/05 11:52 AM Testing Binoculars in the Store Before Buying EdZ   01/15/05 09:29 PM In Pursuit of Cheap Binoculars. What to Expect. EdZ   12/30/04 12:07 PM Handheld Binocular Observing EdZ   12/29/04 07:30 AM Fixed Focus Binoculars EdZ   12/16/04 12:08 PM BINOCULAR OBSERVING REPORTS AND TARGET LISTS EdZ   12/10/04 06:42 PM Depth of Field and 3D or not 3D! EdZ   12/10/04 06:36 PM What can be Seen in Various Sizes Binoculars EdZ   09/19/04 06:21 PM Philosophy and Binocular Ownership by Bill Cook EdZ   09/12/04 03:30 PM Affect of Eye Pupil on Binocular Aperture EdZ   07/22/04 11:38 AM Favorite Binoculars in Various Sizes EdZ   07/22/04 11:37 AM Best binocular overall or in a given price range EdZ   07/22/04 11:36 AM MEASURING / TESTING Optical Aspects of Binoculars EdZ   03/21/04 03:30 PM Contrast EdZ   03/20/04 08:48 PM Need Binocular Collimation or Repair? EdZ   03/17/04 12:08 PM Cleaning Lenses - Binoc Repair Eyeguards - Caps EdZ   03/15/04 09:36 AM If They Look the Same, What Could be Different? EdZ   03/15/04 07:06 AM Binocular Articles over on the Reviews side of CN EdZ   03/03/04 10:55 PM ABERRATIONS AND DEFICIENCIES EdZ   03/02/04 06:49 AM How to Focus Binoculars EdZ   02/07/04 10:18 AM Binocular Mounts - Tripods - Adapters - Motions - Homemade EdZ   02/07/04 10:17 AM PRISMS - BaK 4 vs BK 7 - Roof vs Porro EdZ   02/06/04 11:49 AM Edge Performance - Sharpness of Field EdZ   02/06/04 11:48 AM Terrestrial Viewing EdZ   02/05/04 06:23 AM Resolution and Visual Acuity EdZ   02/03/04 09:10 PM Aperture / Magnification relationship - Exit Pupil EdZ   02/03/04 09:04 PM Coatings EdZ   01/25/04 09:31 PM Zoom Binocular Cautions! EdZ   01/25/04 08:58 PM Exit Pupils 5mm vs 7mm EdZ   01/25/04 07:50 AM AFOV vs. TFOV and Separations for Measuring EdZ   01/24/04 01:48 PM Twilight Factor - Visibility - Binoc Index EdZ   01/24/04 01:43 PM Extra information 12 registered and 10 anonymous users are browsing this forum. 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