Telescope Reviews: Prism leakage concerns

I am in the process of buying some Minox BD 10X58 ED BR binoculars. They are second hand but basically ‘as new’. My friendly optics dealer has let me test for a few days prior to buying them. These are not inexpensive binoculars - approx $US800 which is about half the price new where I live [New Zealand.] The new price in the US is about $US1040.

The views through the 10x58 ED’s are impressive - bright contrasty and very sharp with a well corrected field. There is very little distortion with just a small amount of astigmatism at the edge.
The objective tubes are well baffled. The FOV is a reasonable 6.2 degrees. Eye relief is excellent.
They are a solid 1490 grams / 52 oz. There are no obvious internal reflections. CA is very well suppressed and basically not existent - the lens being made of ED / Fluorite glass.
My brief impression is that they are very nice astro binoculars.

However my main concern is that a ‘moderate’ amount of prism light leakage is present - this is noted at 12, 4 and 8 o’clock. The exit pupils are perfect.
I am concerned [and surprised] at the amount of prism leakage esp. when one considers these are reasonably ‘top end’ binos.
Prism leakage is undesirable and I believe is caused by ‘inferior’ prism design. I also understand it can affect contrast and cause secondary images.
I briefly looked for prism leakage in some other roof and porro prism binoculars.
The Pentax 20x60 PCF 11 – no leakage seen, Orion Resolux 15x70 - no leakage, Oberwerk 25x100 - no leakage, Nikon Monarch 10x56 - very minimal amount observed and Meade 9x63 - moderate amount of leakage and similar to the Minox’s.

I would appreciate any ones comments or ones experience with this issue.
Is this such a concern that I should seriously re-consider buying the Minoxs ?

Thanks for any feedback.

Chris

35 binos.
80mm Cat.
WO66ED
SV NH 80mm / EQ3
Meade 8in.LX90

Edited by charen (07/01/08 03:05 AM)

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