Telescope Reviews: Oberwerk Ultra 15x70 Tests and Evaluation

This series of posts was cut out from under the Kunming thread title and reposted with a new title. this thread is exclusively testing of the Oberwerk Ultra 15x70.

Oberwerk Ultra 15x70
Eye Relief
Tripod Adapter
Prism Light Cutoff
Exit Pupil Illumination

Some of the first few things you notice about this new binocular.

Well, it's heavy, about 5 1/2 pounds.

The eye lens is deeply recessed. I measured the recess at 8mm. With the eyecups folded down for use with eye-glasses, I measured the exit pupil distance at 11-12mm behind the eyecups. So exit pupil distance is about 19mm, but useable eye relief is 11-12mm. I was just barely able to see all the edges of the field of view with my glasses on.

The screw slot for the tripod adapter is recessed about 3-4mm in from the body of the prism housing. That means that you cannot use a typical wide flat binocular adapter with these binoculars, it would rub on the housing, marring the rubber coating, or it may not even screw in. A very nice sturdy narrow (Pentax shaped) metal adapter is provided in the case with the binocular. It works very well.

Both prisms completely span the entire prism shelf. There are no edges of prisms exposed. However, the backside of the front prism protrudes slightly into the light path. I could see it in both barrlels. This causes what we refer to as prism light cutoff. It was barely perceptible in the exit pupil. Without measurement, I would estimate the cutoff at 1-2%. Keep in mind this is blocking light only from the outer few mm of the objective lens. Considered inconsequential.

Now here's a real nice piece of information. This is definitely NOT one of the first things you notice, but it is one of the first things I wanted to measure. A profile of the exit pupil illumination.

The illumination of the exit pupil is what Roland Christen talked about in some of his comments. This binocular has a very well illuminated exit pupil. I include a graphic attachment here showing a comparison of the Ultra 15x70, Fujinon FMT-SX 16x70 and the Oberwerk 2003 15x70. The Ultra lies in between them, but it is far closer to the Fujinon.

The Fujinon comes out on top for all light entering at any point on the objective within the central 50% of the lens. Exit pupil illumination drops consistently as the source light enters further out on the objective lens. Light entering the objective at 50% out from center illuminates the entire Fujinon exit pupil. In the Ultra, it illums about 85% of the exit pupil. Shortly after a point 70% out from center the Ultra overtakes the Fujinon.

Light entering at the very edges of the objective leaves the central 20% of the Fujinon completely dark. 40% of the 2003 Obie 15x70 is left dark. Only the central 4% of the 15x70 Ultra is dark. The Ultra is clearly the winner here.

For those who like to interpolate, you can find the point where they cross. Some of you may remember my laser tests from a few years ago. This is the laser test repeated. Some day I'll plot all this stuff.

Fujinon FMT-SX 16x70
exit pupil is 100% illuminated by light at 50% out from center
exit pupil is 50% illuminated by light at 90% out from center
exit pupil is 40% illum (20% dark) by light from the very edge of the objective

Oberwerk Ultra 15x70
exit pupil is 100% illuminated by light at 45% out from center
exit pupil is 50% illuminated by light at 96% out from center
exit pupil is 48% illum (4% dark) by light from the very edge of the objective

Oberwerk 2003 15x70
exit pupil is 100% illuminated by light at 40% out from center
exit pupil is 50% illuminated by light at 83% out from center
exit pupil is 30% illum (40% dark) by light from the very edge of the objective

For comparison I include here one of the best performances I have measured, the BT100 with 14mm Radians. I also include the Fujinon FMT-SX 10x70, not the worst binocular measured, but I found the comparison to the Ultra intersting.

Fujinon FMT-SX 10x70
exit pupil is 100% illuminated by light at 35% out from center
exit pupil is 50% illuminated by light at 85% out from center
exit pupil is 35% illum (30% dark) by light from the very edge of the objective

Oberwerk BT100 with 14mm Radians
exit pupil is 100% illuminated by light at 65% out from center
exit pupil is always more than 50% illuminated
exit pupil is 55% illum (0% dark) by light from the very edge of the objective

Since I sometimes have trouble accessing attachments through a firewall, I also include here a link to the same graphic posted as a jpg in my gallery.
Exit Pupil Illumination Profile of the Ultra 15x70

much more to come.

edit 8-31 9pm revised attachment

edz

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Teach a kid something today. The feeling you'll get is one of life's greatest rewards.
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Edited by EdZ (09/15/06 06:50 AM)

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