The illustration is schematic. For example, the pair of eyes and the two barrels are made one.
The green, central part is what you see, the image and the apparent FOV.
The light green areas are what the human visual field perceives.
The grey area is what's beyond the human visual field (slightly beyond 180 degrees).
Finally, the red area is what is obscured by the field stop, the rims, the housing of the bnoculars and the hands. One might call this "negative PFOV".
If the hands are further away from the eyes they will obscure less of the human FOV.
# I is a non-wide angle binocular with the eyecup extended.
# II is the same sample with the eyecups collapsed.
# III is a wide angle binocular with the eyecup extended.
# IV is an equally wide angle bin with sleek eyecup design and eyecups collapsed.
The image portion of # III is greater than # I and the obscured part of the visual field is smaller.
Same thing happen between #II and # IV, but the sleek eyecups of # IV adds a few extra degrees of PFOV. If the eye relief allows holding the bins further away, the open area will increase, and the hands will get more out of the way.
As follows, a great AFOV is advantageous for the walk-in experience because it expands from the center towards the obscuration.
But if the outer edge of the obscuration/"negative PFOV" is further out, it will decrease the PFOV.
So, as little obscuration as possible is desired. IMHO.
Last edited by looksharp65 : Saturday 14th January 2012 at 10:30.