Eye focus.

[Bigbear]

I'm not sure what the correct term is for this, and I apologise if this is a stupid question.

When I use the Bresser 10x50 bins, I notice that when I focus the bins on a mid-distance object, I find that I don't need to adjust the focus again for further objects.

It seems my eyes are compensating for the distances.

Is this my eyes focusing automatically and/or getting used to looking through the bins?

[Capricorn]

2 things will come into play.

As you say your eyes will comoensate a little for the difference in "distance" as they do when you are simply walking round looking at things.

Next is the depth of focus and depth of field of the binoculars. In effect the binoculars are focussed maybe at a specific target at whatever distance but there are items in front and behind that will also fall into focus.

It is an odd thing about binoculars that the better they are the the less these fields are, but usually the sharper objects are when in them. Some like a short depth of focus and field some don't. I do not particularily as it means almost constant refocussing.

The "problem" of your eye adjusting is that whatever you are looking at is not at the eyes rest point so some compensation is taking place which if you are looking a lot could cause some strain and tiredness. Which is most likely what happens when some people look though optical equipment, they try to do the focusing and don't allow the equipment to do it for them.

[Bigbear]

Thanks for the reply, guess that it is normal.

I did notice that my eyes do get tired after a long time looking, so I shall try and play around slightly with the focus.

Thanks again.