Cameras and Lenses

Xian Vision: ED bins and 90% transmission

Xi'an Vision Opto-Electronic Co. have updated their web site (still a bit funky) but they have a new range of products.

http://www.aoi.com.cn/new%20product.htm

Some are revamped version of their older Navigator range (e.g. REI XR bins, Williams APO) with claimed 90% transmission in 25mm, 32mm, 42mm and 50mm objectives. These had rather short bodies and rather too much CA in their previous incarnation for me but maybe they improved the EP design to reduce lateral CA?

I presume they've improved their AR coatings and perhaps are using dielectric mirrors in the roof prisms. They're not explicit on the latter point. But these are very high numbers (Zeiss FL 7x42 at 93% is mentioned elsewhere on BF). So they're either real or they're not quite telling the truth!

The Pioneer, an open bridge ED 8x40ish bin with a wide FOV.

http://www.aoi.com.cn/2319.htm

It's difficult to tell but I don't think that's the same enclosure as the other Chinese ED bins. We've seen a couple of other enclosure designs on announced Chinese bins). Or the photo may just be a little stretched

They claim a wider FOV than any of the other Chinese ED bins including 7 degrees for a 10x bin!

Mag 8x 10x
Degree 8.3 7
ft /1000 yds 438 367
m/1000m 146 122
ER 18.5 17

I wonder what the edges of the field look like?

They also have series of 50mm spotting scopes (10x, 12x, 15x and 20x) that look like half a roof prisms bin. Never seen anyone do this before with a roof. Very odd. Tripod mountable. Might make a good monopod spotter? The ER falls off rather alarmingly though.

http://www.aoi.com.cn/7101.htm

They also have a selection of porros mostly big for astro use and colorful for marine use.

And what I was looking for the a center focus Xian Ares 8x30 porro. And although they got my hopes up by calling it a ZCF on the high performance page.

http://www.aoi.com.cn/high%20performance.htm

... it's still only in IF. But with claimed 95% transmission.

http://www.aoi.com.cn/2503-02.htm

Shame. Holger really liked it. And I hear it's used and well liked in Afghanistan too.

http://www.holgermerlitz.de/ares8x30.html

Here is a question for you. I have often seen folks mentione 90% plus light transmission figures but I often get the impression that the folks in marketing and the folks in engineering get their signals crossed. Is it 90% per glass surface or 90% overall?

That claim would be for the whole instrument. Even uncoated glass transmits 95-96% of light per surface.

A single transmission number might be accurate, but still not be very useful. Does it represent the peak transmission at a single wavelength? If so, what wavelength and how steep is the loss of transmission away from the peak? The best information would be a graph of the transmission curve plotted across the entire visible light spectrum. Second best would be transmission figures for 555nm and 510nm, which represent peak sensitivity of the eye in daylight and very dim light.

It's not unusual for a binocular to have peak transmission somewhere between 570 and 630nm. Transmission at 555nm may be down 3-4% from the peak and transmission at 510nm may be down 6-8% or more.

The measurements themselves can vary with different lab equipment and techniques. I saw some tests of the very same binocular specimens measured by Leica and Swarovski which showed differences of as much as 3%. And finally there is sample variation in coating batches that could cause as much as 3-4% difference in the same model binocular.

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