# How the Contax G1 Works

How the Contax G1 rangefinder camera measures distance, focuses its lens, opens its shutter and winds film with motors and a separate viewfinder window\.

By clever\-comet\-621d5664

Topic: Machines

[Open the interactive Jig](https://ask.jig.com/j/QmjbEpnak47T)

## Transcript

### 1. Meet the Contax G1

This is the Contax G1, a film camera from Japan first sold in 1994\. It looks simple, but inside it measures distance, focuses the lens and winds the film all by itself\. Let's open it up and see how\.

The body is about 13 cm wide and weighs about 460 g without film or batteries\.

### 2. You look through a window, not the lens

Many big film cameras let you look through the lens itself\. The G1 has its own small window, called a viewfinder, up beside the lens\. Your eye looks through that window to frame the picture\.

The window sits a little to one side of the lens, so up close it sees from a slightly different spot\. The camera shifts its frame lines to make up for it\.

### 3. A window that zooms

Some lenses see wide, others see narrow\. When you fit a lens, little lenses inside the viewfinder slide to match it, so the window shows what the photo will show\. Try the three lens sizes\.

The viewfinder matches lenses from 28 mm \(wide\) to 90 mm \(narrow\)\. This cutaway is a simplified picture of the real optics\.

### 4. Two eyes judge distance

The two small windows on the right are the camera's autofocus eyes\. Each one sees the toy from a slightly different spot\. The closer the toy, the more steeply their sight lines lean together\. Move the toy and watch\.

It works a bit like your own two eyes\. The G1's eyes need light and some pattern to look at, because they send out no beam of their own\.

### 5. The body turns the lens

The lens has no motor of its own\. Press the shutter button halfway and a motor in the body spins a tiny drive shaft in the lens mount\. It screws the glass forward or back until the picture is sharp, then a green light says ready\.

The glass moves forward for near things and back for far ones\. This 45 mm lens can focus as close as half a metre\.

### 6. A curtain of light

Press all the way and the shutter opens\. Two thin curtains just in front of the film race down, one after the other\. For a split second light passes through the gap and paints the picture onto the film\.

The fastest speed is 1/2000 of a second\. In dim light the camera can keep the shutter open for up to 16 seconds\.

### 7. Whirr\! The film winds itself

After every photo a motor turns the take\-up spool and pulls the film along to a fresh, unused frame\. There is no lever to wind\. At the end of the roll the motor pulls all the film back into its cassette\.

It can take about two photos every second\. Two small batteries power the motors, the eyes and the shutter\.

### 8. A clever team of parts

A window to look through, two eyes to measure, a motor to focus, curtains to let in light and a spool to wind\. Each part does one job, and together they turn a single press into a sharp photo\.

Its shiny skin is titanium, wrapped over a strong aluminium frame\.