120 roll film was originally introduced in 1901 by Kodak for the no. 2 Brownie box camera. This film was designed to produce 6x9 images and was soon adopted for use by many manufacturers. Until the end of the 1930’s this film only had a single line of numbers (1 to 8) on the backing paper.
When Zeiss-Ikon introduced the 6x4.5 format, there was no numbering for 6x4.5 photography. As a work-around, Zeiss solved the problem by installing two red counter windows in the 6x4.5 Super Ikonta A and the 6x9 Super Ikonta C cameras. As a result, when shooting 6x4.5 BOTH red counter windows must be used.
The 6x4.5 reduction mask:
The reduction mask which fits into the 6x9 Super Ikonta is composed of two "flaps" interconnected with spring steel wire. This construction allows it to flex in the middle in a slight bow so that it can be inserted into the camera.
To use the 6x4.5 reduction mask in a 6x9 Super Ikonta camera, simply open the back of the camera. Insert the edge of one "flap" into the film gate. Then take the remaining "flap" between your thumb and index finger and pull it slightly towards the first flap. This action will cause the spring wire to flex slightly reducing the overall length of the mask. Now insert the remaining flap edge into the film gate and then relax your grip. You may have to wiggle it a bit but both flaps should sit flat and flush in the film gate now. If everything went well, the mask is now securely clipped into place. (Some users may prefer to extend the bellows so that the edges of the film gate is easier to see.)
How to use the dual counter windows:
The proper way to do this is load film into your camera. Then wind the film carefully until number “1” appears the first counter window. It is now ready for the first exposure. After this photo is taken, carefully wind the film until the same number “1” appears in the second counter window. Now take your second photo. After that, wind the film until number “2” appears centered in the first counter window. Take another photo. Then wind until the number “2” appears in the second window. Then shoot again. Repeat this sequence for all of the other following numbers until you finish the roll. (The sequence ends with number “8”.)
Why are we doing this?:
By using the numbers twice, what you are actually doing is placing two half frame (6x4.5) exposures, on a section of film intended for a single 6x9 exposure. Since 2x8=16 you will end up with sixteen 6x4.5 exposures on a single roll of 120 film.
Don’t forget the viewfinder:
By the way, don’t forget to set the viewfinder to the appropriate format. Early model Super Ikontas viewfinders have a mask built into them. On some of them the 6x4.5 mask can be locked into a downward position with a lever. Other versions have a spring clip that holds it. The later versions (with the mirrored Albada finder) have lines for both formats built into the viewfinder.
What about 6x9?
When shooting 6x9 with the larger 6x9 Super Ikonta you only use one red counter window. It usually has 6x9 pressed into the leather with rather small letters. That’s the one you want.
What the story with 120 film now?
At some point during the late 1930’s there were so many camera using 120 film in various formats that film producers started selling films with additional lines of numbers for 6x6 and 6x4.5 That’s still the case now with our “modern” 120 film. A manufacturer only has to locate a red window correctly to reveal the desired line of numbers.
I hope this helps you enjoy your camera!