Stephen Prower
Well-known member
Swift Osprey: Getting full field of view & Seeking to eliminate blackouts
1. Introduction: People complain of the 'tunnel like' field of view of the Swift Osprey. Simon Spiers said that a restricted field of view detracted from the otherwise very good performance of his Osprey. That was my experience too. I was also distracted in my view through the binocular by frequent blackouts.
The other day, having successfully carried out a couple of simple fettling and customising jobs on binoculars, I set about trying to crack the two problems. As regards the field of view, I was successful. As regards the blackouts, I reduced them in number to the much smaller incidence of blackouts that I was used to in similar old models of binocular
2. Conclusions: I drew from the exercise the following conclusions.
Perhaps more so than other binoculars, in order to get the full 7* field of view of the Swift Osprey the binocular must come to the eyes with the eyes of the user both precisely, as matter of the height of the eyecups, and consistently, as a matter of the comfortable fit to face of the binocular, located at the point of eye relief.
As described on the Forum, too high a location above the point of eye relief and the field of view will be restricted; too low and the user will experience incipient blackouts and view a distracting bright ring round the edge of the field stops.
Even so the user may still experience blackouts in ordinary use of the binocular from other causes. By making micro-adjustments to the Inter-Pupillary Distance of the binocular, I achieved a setting that largely eliminated such blackouts. I don't have a figure of my own Inter-Pupillary Distance, but I would assume that the figure is the same figure as the figure of the Inter-Pupillary Distance of the binocular that I arrived at
3. Method & Findings: The parameters of the Osprey that were available to me to adjust were:
a) The width of the eyecups
b) The height of the eyecups
c) The inter-pupillary distance of the binocular
Width of eyecups: My comfortable 'fit to face' range for the width of binocular eyecups is 43-46mm. The original width of the Osprey's eyecups is 36mm. I use bicycle inner tubes to bulk out the width of binocular eyecups. I bulked out the eyecups to achieve a total increase of 9mm in their width, or a new total width of 45mm.
The figure of 45mm gave me a comfortable fit of the eyecups to face
Height of eyecups: I usually find that the height of binocular eyecups is too low for me.
So first, using rubber bands cut from bicycle inner tube, I froze the eyecups of the binocular in the 'Up' position. Second I increased the height of the bicycle inner tube that I had sleeved over the eyecups when bulking them out by small increments above the rim of the eyecups.
I found that the best compromise setting as between too low a height (bright ring & blackouts), and too high (restricted field of view) was an increase of height of about 3.5mm
Inter-pupillary distance of binocular: I have no means of physically measuring the figure of my personal Inter-Pupillary Distance as user.
So I took the figure to be the same 64mm figure that I usually find to be satisfactory when adjusting other binoculars, and used it as my starting point for adjusting the Inter-Pupillary Distance of the binocular.
I then adjusted the Inter-Pupillary Distance of the binocular by small increments until I had achieved a best setting figure, which was also a figure of 64mm
5. Result: In the event the three settings that I chose were successful. I achieved the full potential field of view of my Swift Osprey. I still get occasional incipient blackouts; however they are now more of a fleeting distraction than a serious problem.
6. Addendum: The further question that I should answer is:
'Did I achieve a favourable result partly or wholly by virtue of a happy personal combination of choices of dimension: eyecup width of 45mm for comfort and consistency, and eyecup height of 3.5mm for precise alignment of the eyes with the point of eye relief?
I think that the answer is certainly yes.
The Osprey does seem to me to be over-sensitive to the inexact positioning of the eyes at the point of eye relief. The oversensitivity is aggravated by the discomfort, and consequent inconsistency of positioning the eyes, that results from its narrow eyecups.
But what an excellent binocular the Osprey is when sorted. Even when I bought it some ten years ago, when I had to choose between the Osprey 7.5x42 7.0* and an owned from new Nikon Action VII 7x35 9.2* to give away to a friend, after agonised side-by-side comparisons the Osprey won. But the weight of the Osprey told, and it was eventually supplanted by an Opticron 8x32 SR.GA.
I am now glad that I nevertheless kept the Osprey!
Stephen
1. Introduction: People complain of the 'tunnel like' field of view of the Swift Osprey. Simon Spiers said that a restricted field of view detracted from the otherwise very good performance of his Osprey. That was my experience too. I was also distracted in my view through the binocular by frequent blackouts.
The other day, having successfully carried out a couple of simple fettling and customising jobs on binoculars, I set about trying to crack the two problems. As regards the field of view, I was successful. As regards the blackouts, I reduced them in number to the much smaller incidence of blackouts that I was used to in similar old models of binocular
2. Conclusions: I drew from the exercise the following conclusions.
Perhaps more so than other binoculars, in order to get the full 7* field of view of the Swift Osprey the binocular must come to the eyes with the eyes of the user both precisely, as matter of the height of the eyecups, and consistently, as a matter of the comfortable fit to face of the binocular, located at the point of eye relief.
As described on the Forum, too high a location above the point of eye relief and the field of view will be restricted; too low and the user will experience incipient blackouts and view a distracting bright ring round the edge of the field stops.
Even so the user may still experience blackouts in ordinary use of the binocular from other causes. By making micro-adjustments to the Inter-Pupillary Distance of the binocular, I achieved a setting that largely eliminated such blackouts. I don't have a figure of my own Inter-Pupillary Distance, but I would assume that the figure is the same figure as the figure of the Inter-Pupillary Distance of the binocular that I arrived at
3. Method & Findings: The parameters of the Osprey that were available to me to adjust were:
a) The width of the eyecups
b) The height of the eyecups
c) The inter-pupillary distance of the binocular
Width of eyecups: My comfortable 'fit to face' range for the width of binocular eyecups is 43-46mm. The original width of the Osprey's eyecups is 36mm. I use bicycle inner tubes to bulk out the width of binocular eyecups. I bulked out the eyecups to achieve a total increase of 9mm in their width, or a new total width of 45mm.
The figure of 45mm gave me a comfortable fit of the eyecups to face
Height of eyecups: I usually find that the height of binocular eyecups is too low for me.
So first, using rubber bands cut from bicycle inner tube, I froze the eyecups of the binocular in the 'Up' position. Second I increased the height of the bicycle inner tube that I had sleeved over the eyecups when bulking them out by small increments above the rim of the eyecups.
I found that the best compromise setting as between too low a height (bright ring & blackouts), and too high (restricted field of view) was an increase of height of about 3.5mm
Inter-pupillary distance of binocular: I have no means of physically measuring the figure of my personal Inter-Pupillary Distance as user.
So I took the figure to be the same 64mm figure that I usually find to be satisfactory when adjusting other binoculars, and used it as my starting point for adjusting the Inter-Pupillary Distance of the binocular.
I then adjusted the Inter-Pupillary Distance of the binocular by small increments until I had achieved a best setting figure, which was also a figure of 64mm
5. Result: In the event the three settings that I chose were successful. I achieved the full potential field of view of my Swift Osprey. I still get occasional incipient blackouts; however they are now more of a fleeting distraction than a serious problem.
6. Addendum: The further question that I should answer is:
'Did I achieve a favourable result partly or wholly by virtue of a happy personal combination of choices of dimension: eyecup width of 45mm for comfort and consistency, and eyecup height of 3.5mm for precise alignment of the eyes with the point of eye relief?
I think that the answer is certainly yes.
The Osprey does seem to me to be over-sensitive to the inexact positioning of the eyes at the point of eye relief. The oversensitivity is aggravated by the discomfort, and consequent inconsistency of positioning the eyes, that results from its narrow eyecups.
But what an excellent binocular the Osprey is when sorted. Even when I bought it some ten years ago, when I had to choose between the Osprey 7.5x42 7.0* and an owned from new Nikon Action VII 7x35 9.2* to give away to a friend, after agonised side-by-side comparisons the Osprey won. But the weight of the Osprey told, and it was eventually supplanted by an Opticron 8x32 SR.GA.
I am now glad that I nevertheless kept the Osprey!
Stephen
