The Leica camera was invented by Oskar Barnack, who was born in Lynow, Brandenburg, Germany, on November 1, 1879⁴⁶¹. After spending many years working in the optical-mechanical industry, he joined the experimental department of the Leitz company in 1911⁴⁶¹. There, he successfully solved several challenging design problems⁴⁶¹. By this time, Barnack had also begun to take a keen interest in motion photography, which was still in its early stages⁴⁶¹.

By 1912, he had designed and constructed his own movie camera, which he later used successfully in the production of several films for his employers⁴⁶¹. The prohibitive cost of exposing film in bulk, without being absolutely certain of the exposure correctness, prompted Barnack to devise a small still camera that utilized motion picture film⁴⁶¹. He initially aimed to use it for test exposures; however, he realized that the standard cine frame size of 18x24 mm was too small to be practically useful with the materials available at the time⁴⁶¹. As a result, he decided to double the height of the cine frame, inadvertently creating the 24x36 mm format that has since become universally known as the Leica size⁴⁶¹.

Once he decided on the negative size, Barnack focused on the mechanical aspects of his camera⁴⁶¹. He constructed two camera bodies, Ur-Leica Prototype 1 and Ur-Leica Prototype 2...⁴⁶¹

Barnack's own depiction of the early days was included in the 2nd issue of 1960 Leica Fotografie article authored by Horst Bredow⁴⁷¹: 

"It was about the year 1905. At that time I was using my big 13 × 18 cm plate camera, with 6 double plate holders and heavy leather case like a sample case. These were my miscellaneous impedimenta when I made my precarious way of a Sunday to the Thuringian Forest. As I struggled panting to the summit (particularly as I was somewhat asthmatic up there the thought must have come to me: Isn't there some other way? Anyway I do remember very clearly how I started to experiment with 13×18 cm plates; cutting them up into small separate pieces and with a special gadget and a short focus lens taking about 15 to 20 pictures in a row. But it was a dead failure. The enlarged prints (on account of the excessive grain of the plate) could hardly be called attractive. I let the whole thing simmer for a bit, but none the less the idea of the 'small negative and large print' for still cameras had in fact been born. Meanwhile a big change had taken place in my mode of employment, for in 1911 I entered the Ernst Leitz Optical Works at Wetzlar. Here my sphere of activity, among other things, extended to cinematographic technique.

In 1912 I built my first cine camera and soon realized that the solution of my problem lay in the fine grain of the cine film. An enlargement to postcard size from a cine film frame was quite acceptable. But in the meantime I had become more critical. The postcard and still more the 6x9 print make nice souvenirs: pictures proper only begin at 13x18 or even 18x24 cm, and even these begin to look very small when one has seen prints 50 cm wide. There is no getting away from it that the larger the print the more three-dimensional and realistic it appears.

For enlargements of this size the cine film frame was too small. Since on account of the wonderful invention of standardization this could not unfortunately be made any wider, in order to utilize the film to the utmost I had to make the best possible use of the length.

I chose the double cine frame and found it worked very well, giving a picture 24mm wide, 36 mm long. That is how the LEICA format came about. Not the result of months of brooding, as frequently was to be the case with other, sometimes quite insignificant looking camera parts. The aspect ratio of 2:3 I still feel today is the most attractive and most conve-nient. Next came the actual designing of the LEICA, and to my predilection for the unusual and novel I gave full rein. My activities were not bound by any specific order, or restricted to any particular direction as is usually the case in a modern drawing office: I enjoyed rather the status of a private dilet-tante. In such conditions, untrammelled by conservative notions and utilizing practically none of the principles which had always been regarded as the essential basis of a good camera, this new type camera took shape. From the outset, it was basically the same as it is today. Departures from the original design comprised the fact that in the first model the focal plane shutter did not have an adjustable slit, but made use of a 4 cm wide fixed slit with a number of different spring tensions; also there was no daylight loading cassette. Otherwise everything was there. Above all, the coupling between film wind and shutter. I worked for many years with this first model and I still have many pictures taken with it at that time.

However the outbreak of war put an end for a time to any further development of the camera.

There were more important things to be done. Nevertheless from the many photographs taken in the course of the world war I collected extremely valuable experience, so that when later on the question of manufacture was discussed I was able to bring out the production model in a fairly short space of time.

There were still problems of design to overcome: a rangefinder for close-up exposures—an absolute necessity for a film camera without a focusing screen; an absolutely reliable self-capping focal plane shutter of variable slit-width; and finally daylight loading by means of cassettes. The viewfinder, too, I designed at this time. Having, as I believed, satisfactorily solved these important problems, there remained only one major need —a suitable lens.

This of course had to be of quite superlative quality, since an enlargement of 10x was the very least that would be required of it. That is where the work of Prof. Max Berek came in.

He succeeded in computing an f/3.5 anastigmat of 50 mm focal length which could only be described as at least equal to the very best of its kind. This played a considerable part in getting the whole miniature camera programme under way. At first quite slowly, then at an ever increasing rate, an increase, more-over, which exhibited a noteworthy uniformity from year to year. That is what one can rightly term sound development⁴⁷¹."