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#1
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Bresser Spezial Jagd 9x63 binoculars
Hi
Is there anyone out there who has a pair of Bresser Spezial Jagd 9x63 binos who can comment on their performance. I am particularly interested in the effective aperture of the 63mm objectives. I currently have a pair of Bresser Linear (Meade) 9x63 binos and am disappointed that a plastic ring on the inside of the objective lens reduces the effective aperture to a mere 56mm. Any comments would be much appreciated. Thanks Andy. |
#2
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Don't buy the Bresser 9x56s ? ;-)
* Chris.B |
#3
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Any specifics are possible alternatives would be much appreciated.
Andy. wrote in message ups.com... Don't buy the Bresser 9x56s ? ;-) * Chris.B |
#4
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There is the possiblity that the ring you see is not stopping down the objective lens as much as you think or even at all. The objective is surely at least a doublet. As light rays pass through the two lenses of the doublet, the rays are bent, converging. The cone of light does not exit the back end of the doublet at the same diameter the rays enter the front end. They do converge and more so than a simple cone at the focal length of the binocular would show they converge. Conceivably, for example, rays could be entering a 63mm diameter doublet and exiting the back end of the doublet at only 55mm before the light cone procedes to travel any further into the binocular. If the ring you see is wider than the diameter of the converged rays exiting the back end of the doublet, then there is no light cutoff. If you could focus the binoculars on infinity and then get a precise measurment of the exit pupil (assuming magnification is as stated, which is a broad assumption) you could perform a check on the effective aperture. Don't close focus to test exit pupil as magnification is always higher at close focus and exit pupil will always appear smaller. So, in fact, the ring might not cut off any light at all. edz |
#5
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wrote in message
ps.com... There is the possiblity that the ring you see is not stopping down the objective lens as much as you think or even at all. [snip] A cheap laser would soon show you what is, or is not, getting through - but don't use your eye to check, use a piece of card. Grim |
#6
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Grim wrote:
A cheap laser would soon show you what is, or is not, getting through - but don't use your eye to check, use a piece of card. Grim That would show you vignette in the prisms, but that would not show you if the aperture ring is reducing the aperture. Checking magnification and then checking exit pupil will verify effective aperture. edz |
#7
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Oops. It might. However, still, exit pupil and magnification will
verify exact effective aperture. edz |
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