A Classic Pocket Binocular: The Swift Compact MK III 8 x 20.

A classic Japanese-made Swift Compact MKIII 8 x 20 pocket glass and leather pouch.

A Blog Commenced July 26 2021

 

It’s no secret that I’ve got a special fascination for pocket glasses. Their charms are obvious; tiny, featherlight weight, and their willingness to travel anywhere with you. So you’ll not be surprised to learn that pocket binoculars are not just a manifestation of the 21st century; they have a long history dating back many decades.

In this blog, I want to showcase a rather intriguing model manufactured by the famous US based optics firm, Swift: enter the Japanese-made Compact MKIII 8 x 20. This afternoon I emailed Swift asking for more information about this model. They responded by saying that this model was sold in the early to mid-1980s for about $70, so about $250 in today’s money.

The instrument has a dual hinge design, allowing it to fold down into a tiny size, 9.5 cm long and 5.5cm wide. Even with its permanently attached lanyard, the instrument tips the scales at only 176g. Not that’s what I call lightweight! I only received a small leather carry pouch with the instrument. It’s textured black on the outside but has a lovely red velvety lining inside. Is it original? No idea!

The Swift Compact MKIII 8 x 20 is still in great mechanical condition despite its age.

The bridge is made from aluminium and is a little thinner than those you’ll find on contemporary models made by Leica and Swarovski, for example. The coatings on the lenses are simple, blue-tinted magnesium fluoride. I’m guessing that all the optical surfaces are fully coated but can’t be sure.

Coatings on the ocular lenses.

Coatings on the objective lenses.

The objectives are quite deeply recessed in this binocular: hopefully this will help protect it from the elements and stray light. The ocular lenses have about 10mm of eye relief; not great by modern standards but par for the course in the 1980s.

The focus wheel is located in the middle of the bridge. It’s small but easy to operate, moving smoothly and accurately. Functionally, it’s very similar to the Leica Trinovid BCA models I showcased some time back. The faux leather and smooth, black metal around the objectives work well together; very Leica-like!

The underside of the binocular showing up the good condition of the chassis. Note the faded inspection sticker on the barrel.

The dioptre adjustment ring is located under the right ocular and has a nicely graded scale. It moves smoothly but has a tendency to wander away from my ideal setting.

Details of the dioptre ring on the Swift Compact MKIII 8 x 20.

The instrument is still in good collimation, but the interior optics have developed quite a thick layer of haze which you can see in the image below of the exit pupils.

Note the prominent haze around the exit pupils.

As you might expect, a glass of this age and condition produces a dim image, with the haze causing quite a bit of extinction. Neither are the roof prisms phase coated, reducing coherent light transmission further. It’s saving grace however, is the sharpness of the image and the great field of view – a whopping 7.25 angular degrees! That’s amazing for a pocket binocular, even by today’s standards. The sweet spot is very large too. I did a star test on Arcturus around local midnight to see how well it maintained its pinpoint sharpness. The results were very encouraging: only in the outer 15 per cent or so did I detect noticeable distortion – a very good result.

I took a single shot image of the field of view through the instrument. I hope you’ll agree it’s quite well corrected!

A single shot image through my Iphone 7 showing the instrument’s sharpness and off-axis performance.

 

These tests persuaded me to have the instrument fully refurbished by professionals.

Insane I hear you say!

But we already live in an insane world, so this project is really small beer in the scheme of things. Besides, I would like to see just how well a high-quality 1980s pocket glass can perform compared with modern instruments.

So, I got on the phone to East Coast Binocular Repairs. After describing the size and make of the instrument and the issue with the haze in the interior, I asked if they’d take a look at it for me and they said yes. So, I packed it off to them via special delivery Royal Mail this afternoon. As soon as I hear more, I’ll report back with further details.

Fingers crossed!

 

To be Continued……

 

De Fideli.

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