Eyeballs and focusing

[Dr Jekyll]

What distance is effectively infinity for a human eyeball?

[bearman68]

Not quite sure what you mean by the question, but given that you can see the stars, some of those are pretty far away. (apparently)

[thebraketester]

At a guess I would say around 20-30 meters. That’s purely looking out of the window and guessing :-)

[Dr Jekyll]

bearman68 said:

Not quite sure what you mean by the question, but given that you can see the stars, some of those are pretty far away. (apparently)

I can, and I can also see my laptop, but my eye has to change focus between them. But I don't think it has to change focus between the stars and the moon, or even the moon and the horizon. I was asking how close a thing I can look at before my eyes have to adjust from astronomy mode.

[bearman68]

Ah OK.
I imagine you have to adjust your focus to make out details on anything that's a different distance away. It's just the amount of adjustment becomes relatively small at large distances - but you still have to make the adjustment.
Just been looking at trees circa 500m away and 700m away, and some small focus adjustments seem to be required.

But I'm old and my eyes are knackered anyway.

[anonymous-user]

What you’re talking about is the Hyperfocal distance I believe. Most reports I’ve seen puts it at about 6 or 7 meters in indoor light. No idea for outdoor light or how much that affects it.

[StanleyT]

bearman68 said:

Not quite sure what you mean by the question, but given that you can see the stars, some of those are pretty far away. (apparently)

If the stars are light years away though, surely the light has come to out eyeballs, rather than our eyeballs focusing on the light of the star?

Obviously short distances we see objects as they are, but at what point are we seeing the light from an object arriving at our eyes, rather than actually looking at the object?

[durbster]

I'm sure I read recently there are genetic, or at least environmental variations of this.

For predominantly outdoor societies (e.g. Australian Aboriginals), their natural focus point is further away because their eyes spend so much time looking into the distance with fewer close landmarks, so the eye is more tuned for that.

I don't know if it still applies to an Aborigine who grew up in a city, however, so it may not be genetic.