Digital Insert for 35mm Film Cameras

Digital Insert for 35mm Film Cameras



Written by Dave Barth, 19 January 2009.

This article is by David Barth, reprinted, with permission, from the Nikon Historical Society Journal.

In the old days, before digital cameras dominated the market, it was easy to dust off a Nikon SP (or any 35mm film camera), load it with film, and shoot some pictures. We can still do that today, but the time is coming when things like film, film processing, and film printing will no longer be easily available. These items will be available from special boutiques, but not from ordinary camera stores.

The use of film will become a low-volume, high-cost hobby. Film cameras would join buggy whips as useless items. But what if someone designed a compact, digital module that would fit into the back of any 35mm film camera? Perhaps the pressure plate would have to be removed to make room. Because the inside of most 35mm film cameras is about the same size, a digital module that would fit one camera would fit nearly all of them.

Leica and Hasselblad have digital backs for their film cameras, but they fit only specific cameras made by the same company, they are heavy and bulky, and they are very expensive, costing around $7,000 for the Leica and $25,000 for the Hasselblad in 2009 dollars.

The proposed digital module would be simple. It would have a fixed ASA/DIN, although upgraded modules might have a manually adjustable setting on the back. The module would consist of an image receptor, a memory card to hold the images, a battery, and electronic circuits to make it all work. The image receptor would fit on the film plane, behind the shutter, in the same location where the frame of film to be exposed was located. The battery and electronics module would fit into the cavity where the film can was placed, linking the exposure switch to the film rewind shaft. The module would imitate film. The procedure for taking digital photos would work something like this:

  1. Open the back of the film camera.
  2. If necessary, remove the pressure plate to make room for the digital module.
  3. Insert the digital module.
  4. Close the back of the camera.
  5. If the camera does not have automatic exposure control, adjust the f-stop and aperture to the correct settings for the light that is available. If the camera has automatic exposure control, no f-stop and aperture settings are needed.
  6. If the lens does not have automatic focus, manually focus the lens.
  7. Turn the rewind knob to turn on the module.
  8. Release the shutter to allow it to pass light to the receptor.
  9. Sufficient light hitting the receptor will cause it to capture the image and store it into the buffer.
  10. If the buffer is full, or at some predetermined threshold, it will move the images from itself to the memory card.
  11. The digital module will automatically shut off.
  12. To take another photograph, repeat steps 5 through 9.
  13. To transfer the images to a computer, open the back of the camera, remove the memory card, and put it into the card reader attached to the computer, and execute the transfer as normal.


Such a digital module would lack a viewing screen on the back of the camera, but one could be on the back of the module, itself, viewable by opening the back of the camera.

It is possible that a full-frame module with 10 megapixels might cost $200. The rationale for this relatively low cost is that there would be no need for all of the "bells and whistles" that most digital cameras possess. The module would not need a body, prism, shutter, mirror, viewfinder, or the associated mechanicals and electronics.

Owners of film cameras might own several of these modules due to their relatively low price and so they would not need to move a module from camera to camera.

The outcome of the availability of such a module might cause the value of film cameras to rise from their currently, dismally low values.

A repeat market could arise as these modules were improved and given greater capabilities. Because this unit would be purchased primarily by collectors, the market would be relatively small. For this reason, it is unlikely that a major manufacturer of digital cameras would undertake to design and manufacture such a module. Instead, it would probably be a smaller company that does not have a major stake in the digital market, such as Cosina, that would build these units.

Without a digital module like the one described here, film cameras will become useless curiosities as film and processing chemicals become scarce. Let's hope that someone can provide a digital module for use in any film camera.