Hello again Mark ,
I'm sure you are correct. . . Regards , Kenny
Hi Kenny: Think really hard before casting this in stone . . . at least for daytime use.
Cheers,
Bill
Posted 08 August 2005 - 10:09 PM
Hello again Mark ,
I'm sure you are correct. . . Regards , Kenny
Posted 09 August 2005 - 01:02 AM
Posted 09 August 2005 - 04:02 PM
Kenny, thanks for clarifying this - at least now I'm assured I'm not misreading things.When I wrote in response to Mark's post " I'm sure you are CORRECT " -- I MEANT to type " INCORRECT ".
Posted 09 August 2005 - 04:26 PM
. . . In repsonse to Bill, I don't (yet) understand how this could be different for night-time versus daylight viewing, other than that of course the eye entrance pupil will be different. But the principle should be the same.
If I'm wrong, then please teach me.
Posted 09 August 2005 - 05:34 PM
Posted 09 August 2005 - 08:28 PM
Posted 09 August 2005 - 08:46 PM
I have been reading this discussion with interest; having a long history of using compact binoculars with <3mm exit pupils I have to agree with Kenny. Small exit pupils do need to be "bang on" or the view suffers.
Posted 10 August 2005 - 01:24 AM
Posted 10 August 2005 - 07:18 AM
Posted 10 August 2005 - 03:03 PM
Posted 10 August 2005 - 03:58 PM
. . . I'm not sure if this is quite related to what you are thinking of Bill.
Posted 10 August 2005 - 08:27 PM
Posted 10 August 2005 - 08:59 PM
Bill,
As far as I know, the size of the exit pupil doesn't have a relation to AFOV as you are implying. Rich V
Posted 10 August 2005 - 09:08 PM
Rich,Bill,
As far as I know, the size of the exit pupil doesn't have a relation to AFOV as you are implying. A small exit pupil from a 70° AFOV eyepiece illuminates the same area of the retina as a large exit pupil from and ep with the same AFOV. The illumination is not as bright but it does cover the same area on the retina.
Posted 10 August 2005 - 09:23 PM
Posted 10 August 2005 - 09:50 PM
You may be right, but intuitively this doesn't make sense. Suppose you have a very narrow pencil of light like a laser beam. Are you saying that if you shine this in the eye the beam will spread to cover the entire retina? If so, how do they perform laser surgery on the retina?
Posted 11 August 2005 - 04:08 AM
What's at stake here is IF the exit pupil is small it must pass through the central sharpest area of the eye's lens. Our vision is sharpest through the central axis of the lens just like a camera lens operates best through it's central axis. I know of no camera lenses that produce as sharp an image wide open as they do stopped down. Our eye lens operates in much the same fashion.
In daytime a small exit pupil produces a sharp image on the retina rather easily as the eye pupil is constricted and all the light must pass through the central axis. You do get a "black out" effect easily since the constricted pupil is a small target.
At night, things are different; now the eye pupil is dilated and it is easier for the small exit pupil to fall off axis in the eye. Careful IPD adjustment is now more important to get the sharpest views. "Black out" is not such a big issue; the dilated pupil is an easy target to hit but if the light cone doesn't pass through the center of the lens image quality suffers.
Rich V
Posted 11 August 2005 - 08:08 AM
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