Looking for real binoculars for my almost 5 yr old son what magnification and brand?

[Beth M]

I am unsure how to understand magnifications on binoculars. There was a 50x30 or 10x25 -- which is better, which would you recommend?

[JimBa151]

The most popular starter (and general purpose) binoculars are 7x35. (7x) is the magnification factor, (35) is the objective (front) lens diameter in mm. Higher power binocs (10x or above) are difficult to hold a steady image in, can be frustrating to all but a very experienced user. (25mm) front lens size will not be good for star-gazing as it limits the light coming in. For a 5-year old who wants to handle them without constant adult supervision and assistance, get him/her a not-so-expensive pair (7x35 Bushnells are very reasonable for the dollar). A child that age can easily damage an expensive pair.

[Carlos_dfc]

Hi Beth
The first number is magnification - the second number is the diameter of the main lenses at the front (the aperture)
So, a 10x25 would give 10x magnification, with a 25mm wide aperture.
Also - divide the aperture by the magnification, and you will get the size of the exit pupil in mm
(the cone of light that exits the eyepieces and goes into the eye)
You want an exit pupil between the sizes of 2mm and 7mm.
Bigger exit pupil = brighter image
And if the exit pupil size drops below 2mm, then the image will be dim even in bright daylight.
For night-time use (astronomy), you want an exit pupil of 5mm or more (4mm exit pupil is acceptable for astronomy use, as long as the aperture is bigger than 50mm)
Good binocular sizes for astronomy are...
7x35, 7x50, 8x42, 8x56, 9x63, 10x50, 11x70, 12x60, 15x70

For a child, avoid magnifications above 10x - in fact, 7x or 8x would be better.
(Above 10x gets very difficult to hold steady enough - for a child, 8x would be a challenge to hand-hold steadily)
I'd second Jim's suggestion of 7x35 for a child - a nice size, with decently bright image, without being too heavy

Oh and avoid the 50x30
50x is FAR too high for binocs - above 20x it gets very difficult to manufacture binocs with both sides of the optics aligned correctly, at 50x they will almost certainly be impossible to align properly, which will induce double-images, that will cause a headache surprisingly quickly
50x30 give an exit pupil of 0.6mm - TINY - these bins would give extremely dim images.




If the binocular spec has 3 numbers, this is a zoom binocular.
The first two nymbers are the magnification range - and as before, the last number is the aperture - so.....
10x30x60 (may also be written 10-30x60)
will have a magnification range from 10x to 30x - with a 60mm aperture
HOWEVER - There is no such thing as a good zoom binocular - avoid zoom binocs like the plague - if you want a zoom, get a 'spotter-scope'

[Beth M]

thank you both for your great responses