A patent filed by Nikon in Japan appears to revive the long-held dream of adding a digital sensor to an existing film SLR. The Japanese Engineering Accomplishment blog found the recently published patent that shows a mechanism for mounting and adjusting the position of a digital sensor on a rear door that could be used to replace the conventional film door. However, the patent only covers the mounting of the sensor relative to the film guides - it doesn't address any of the hurdles that have stood in the way of anyone realizing this long-discussed idea.

Attempts to use digital sensors in film cameras dates back as far as the digital camera itself. The first digital SLRs were significantly-modified Nikon and Canon film models with alternative backs mounted on them. However, attempts to create systems that could be installed in a wide range of cameras, such as Silicon Film, have foundered.

The patent diagram shows a method of fitting and aligning a digital sensor on an alternate back for a film camera.

The most fundamental problems of retrofitting a digital sensor into the film bay of an existing SLR include lack of battery space and the need to constantly open the camera to change ISO, White Balance or any other image setting. And that's assuming many modern photographers would be willing to live without a rear LCD to check their images on.

The Nikon solution appears to involve a replacement back for the camera which would give the manufacturer more flexibility to overcome some of these problems.

However, there are still plenty of engineering challenges to overcome, as the blog post points out. The digital back would need to know when the shutter was being fired, in order to sync its exposure with the shutter's movement. The toppings in front of the sensor (microlenses, low-pass and IR filters) would need to be incredibly thin to avoid fouling the shutter, which is mounted very close to the film plane in conventional SLRs. Finally, existing bodies leave little room to fit the sensor's mounting board if it were to use a full-frame sensor, but using cropped-frame sensor would then require a means of masking the viewfinder to show the relevant crop.

All of these challenges could be lessened if the back were designed in concert with a new camera body.

Consequently, existing film SLR users might not want to get their hopes up too soon - we think it's unlikely Nikon would want to take on these challenges for each of a series of backs to suit the many existing models. Also consider that the number of old bodies can reasonably be assumed to be shrinking as they break or fall into disrepair and that only a proportion of owners would be willing to buy a digital back, and the market for each back looks increasingly small (meaning a handful of users would end up sharing the development cost of each different back).

Many film SLR owners have long harbored the dream of converting their camera to digital. This patent doesn't bring that possibility much closer.

The Engineering Accomplishment blog points out that, if you were to assume Nikon has continued the development of its film cameras, then the F6 is due for a replacement around now. If Nikon is intending to do anything beyond protecting a clever idea one of its engineers had (a fairly common fate for patents), we think it'd still involve having to buy a new camera first. (via PetaPixel)