Mystery Solved – An Eyepiece and a Dial

On Monday, I gave you this mysterious object to identify:

Mystery object. But if you look close, the dial is marked in units of feet.
Mystery object. But if you look close, the dial is marked in units of feet.

The other side looks like this:

With two little window-like openings.
With two little window-like openings.

It was correctly pointed out that the base looks like it would fit on a film camera where the flash might go. But still, what is it?

Shiny and red. Walz is a company in Japan.
Shiny and red. Walz is a company in Japan.

The give-away might be what is on the end of the device, a scale to convert from feet to meters. Why would you need such a thing?

Converting feet to meters.
Converting feet to meters.

This is an old-fashioned rangefinder. Back in the day, cameras didn’t have autofocus. And not all cameras had through-the-lens focusing, either. You had to set the focus based upon what you already knew to be the distance from the camera to the subject.

In order to know that, you needed a rangefinder. Some cameras had them built in. Or you could buy them separately.

Rangefinders work by taking two views of the subject, via the two window at the front of the rangefinder. Then the user looks through the eyepiece on the back and turns the dial until the two images overlap. When they do, the correct range shows up on the dial.

Through the eyepiece. The light spot in the middle is where the two images overlap.
Through the eyepiece. The light spot in the middle is where the two images overlap. It’s hard to photograph, so you can’t really see the overlapping images here.

Then, you simply set the focus on your camera to whatever it needs to be. If you camera’s lens is marked in meters, you can use the converter on the end to get the correct distance in meters.

Then, aim the camera and *click*! You’ve taken a perfect, in-focus picture.

Published by paleololigo

Scientist (Paleontology, Geochemistry, Geology); Writer (Speculative and Science Fiction, plus technical and non-technical Science); Mom to great boy on the Autism spectrum; possessor of too many hobbies.

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