What is the ideal objective size for birding binoculars?

---

What is objective diameter?

The objective diameter of a pair of binoculars refers to the size of the front lenses, measured in millimeters. Generally, a larger objective diameter will result in a brighter and clearer image, as it allows more light to enter the binoculars. However, larger objective lenses also mean larger and heavier binoculars. It is ultimately a trade-off between image quality and portability. A good starting point for most people is a binocular with an objective diameter of around 42 mm.

---

The larger the better?

For birdwatching, a larger objective diameter is generally better as it allows more light to enter the binoculars, resulting in a brighter and clearer image. This can be particularly useful in low-light conditions, such as early morning or late evening when many birds are active. A good objective diameter for birdwatching would be around 42mm-50mm. However, it's also important to consider the magnification and the field of view, the larger the magnification the more narrow the field of view, so it's good to have a balance between magnification and field of view.

---

How do you decide?

Also, it's important to note that larger objective diameter binoculars can be heavier and bulkier, which can be a downside when you're carrying them around all day. Some bird watchers prefer to compromise on objective diameter size and opt for a smaller, more portable pair of binoculars in exchange for slightly less image brightness and clarity.