BirdForum is the net's largest birding community dedicated to wild birds and birding, and is absolutely FREE!

Register for an account to take part in lively discussions in the forum, post your pictures in the gallery and more.

Reply to thread

Message: <blockquote data-quote="denco@comcast.n" data-source="post: 3321499" data-attributes="member: 25300">The Twilight Factor does have important consequences when viewing and trying to see detail in dim light. In low light distance is significant. If you think about it if you are say three feet away from your dog at night in the back yard he is easier to see than if he is thirty feet away. Correct? That is why higher magnification helps in low light. It brings things closer. Here is another explanation:"Twilight factor is a more useful judge of a binocular’s low-light performance than exit pupil, etc., as it takes into account both light transmission and magnification, both of which affect how much detail you can see. Seeing detail is what binoculars and scopes are all about.The larger the image, the easier it is for you to see details in that image. By the same token, with a smaller image, the brighter it gets, the easier it is for you to see the same details clearly. So, within reason, if magnification goes up, brightness can go down without seriously affecting resolution, and vice versa. That is, small bright images can show you as much detail as large dim images.Twilight factor allows you to compare various combinations of aperture vs. magnification to determine the one that best balances an increase in magnification against a decrease in brightness (or vice versa). The larger the twilight factor, the better a binocular is for low-light observing.A twilight factor of 17 and above is best for twilight or early morning use."</blockquote>

Verification