Welcome to Optics Trade debates. In each episode, we talk about a different topic and try to answer the most common questions we receive about it. Today, we are going to talk about fast focus and locking focus on eyepieces.
Most people don't want to shoot with glasses. The diopter setting enables them to achieve the same correction on a riflescope. Other eyesight errors like astigmatism cannot be corrected and in that case, using glasses is unavoidable.
The diopter is set correctly when the user sees the reticle as clear as possible. The easiest way to set the diopter is to put the magnification on the scope to the maximum and point it to a white wall or at the sky (NOT THE SUN) and adjusting the diopter until the reticle is completely clear.
Most modern scopes feature fast focus. Fast focus is easy to use, the diopter setting is adjusted when the ring next to the eyepiece is turned. It's really easily adjustable and can be easily used by people with a different diopter because it's really easy to change.
Locking focus is a little bit different, the diopter setting is lockable with a reverse locking ring. So when the diopter is set it's fixed in place and can't be changed until the locking ring is untightened.
In the past, scopes were made without diopter compensation but nowadays all scopes fall into one of these categories. The predominant of the two is the fast focus, which is used in almost 90% of all scopes.
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Explanation of the term 'fast focus' on our website:
The eyepiece is that part of the rifle scope where you look in.
Fast focus eyepiece is a type of an eyepiece that enables fast diopter settings. With fast focus eyepiece, you can adjust with the rotation of the diopter setting to suit your eyes, reticle and even the target (image) at the same time.
All the newer rifle scopes have fast a focus eyepiece. There are not many rifle scopes without a fast focus eyepiece nowadays.
Older rifle scopes without fast focus had their whole eyepiece rotatable and a counter locking nut.
Riflescopes with fast focus: https://www.optics-trade.eu/en/riflescopes/shopby/special_features-fast_focus.html