What is a good twilight factor for binoculars?

However, the value should always be considered in connection with the exit pupil. The twilight factor of binoculars is a function of the objective lens diameter and the magnification and is between around 5 and 20. The higher it is, the better the resolution (performance) in twilight.

How is twilight factor calculated?

The ‘twilight factor’ can be calculated by first multiplying the magnification by the objective lens diameter and then finding the square root of the result. For instance, the twilight factor of 8×42 binoculars is therefore the square root of 8×42: the square root of 336=18.3.

What is twilight index?

Twilight Factor is a number used to compare the effectiveness of binoculars or spotting scopes used in low light. The larger the twilight factor, the more detail you can see in low light.

What is brightness factor?

If by Brightness factor, you mean Relative Brightness, it is simply the square of the exit pupil value. The Exit pupil value is the Objective lens size (mm) divide by the magnification. So, your example for 10 x 42 mm equals an exit pupil of 4.2 (See Table 1 in the post).

What does exit pupil mean in binoculars?

The exit pupil is the bright circle that can be seen in the center of each eyepiece when you hold the binoculars about 30cm away from your eyes with the objective lenses pointed toward a bright light. Therefore, the diameter of the exit pupil is 5.3mm. This figure indicates the brightness of the image in view.

What is Twilight factor on a scope?

Twilight factor is the measurement of the efficiency of a rifle scope in low light conditions. The higher the twilight factor, the more usable the scope is in twilight conditions. The formula for determining twilight factor is: The square root of magnification times the diameter of the objective lens.

What is relative brightness of the bulb?

The brightness of a lightbulb is given by its power. P = I2R, and so brightness depends on current and resistance. If the bulbs are identical, they have the same resistance. Therefore, when you are asked to rank the brightness of identical bulbs, you are really being asked to rank the amount of current through each.

What is relative brightness in psychology?

Relative Brightness is a comparison of the brightness of any two objects. This can be done through a specific mathematical equation or simply looking at them and making a judgment.

What is the best exit pupil for binoculars?

The ancient dogma on this topic, printed in countless books, says “The human pupil dilates to a maximum diameter of 7 millimeters.” Therefore 7 mm is supposed to be the ideal maximum size for the exit pupil of binoculars or a telescope. This is the reasoning behind the popular 7×50 “night glass” binocular.

Does Barlow affect exit pupil?

Barlows amplify the power of a telescope. The diverging rays leaving the Barlow result in moving the exit pupil further out, thereby extending the eye relief. In short to medium focal length eyepieces the change is not noticeable.

What determines scope field of view?

Generally, the field of view in a scope is determined by the magnification combined with the focal length of the objective/eyepiece combination. Larger fields of view require more sophisticated lens systems in order to maintain good imagery.

What should I look for with Twilight binoculars?

Twilight PERFORMANCE is in my opinion a very important and often underated and overlooked factor with binoculars. Hope this helps – regards -Kenny. So I should pay attention to relative brightness as well and look for a high number there, combined with as high a number as I can comfortably hold in my hands for the Twilight Factor.

What is the relative brightness index of a binocular?

Theoretically speaking, relative brightness index refers to how bright an object ought to be when viewed through a binocular. This index is got by squaring the exit pupil. So let us say a binocular has an exit pupil of 6.25, its relative index will be 37.5.

Which is brighter 8×42 or 8×8 binoculars?

The greater the relative brightness is, the brighter the image will be. With 8×42 binoculars, the brightness is (42÷8)2= 28.1. This means that if the magnification is the same, the larger the effective diameter of the objective lens, the brighter the image will be.

Which is worse 10×50 or 16×50 binoculars?

I’m still not clear about the twilight factor of binoculars, I cannot see how 10×50 which have a factor of 22, would be worse in low light conditions than 16×50 that have a factor of 28, using the twilight factor figures?