A Japanese inventor has filed a patent that could lead to DSLR cameras being able to capture digital video footage.

Hiroshi Terada’s patent manages to bypass inherent problems of the DSLR design – specifically the mirror set-up and auto-focus system – by incorporating a semi-transparent mirror and dual-function AF system into the design.

The semi-transparent mirror would allow a certain percentage – Terada quotes 70 per cent – of light to pass through the camera to the sensor, in much the same way recent live view-enabled DSLRs operate. The deflected 30 per cent, meanwhile, would allow the camera’s continuous phase-detection autofocus to function.

Is there demand for video on DSLR cameras?

The dual-function AF would allow for a wider AF threshold and a slower, smoother AF speed when used in video mode, but would revert to standard AF mode for still photography.

After the advent of live view it was only ever going to be a matter of time before manufacturers decided to tack video shooting onto DSLR models. The big question though, is whether there will be much demand for it. Especially from DSLR purists who tend to view anything that might even remotely compromise still image quality with a high degree of scepticism.

Whinging purists

“There are bound to be purists that whinge, but there always are!" says Chris George, associate editor of PhotoPlus magazine. However at the lower end of the DSLR market, video capture could well appeal to prospective new DSLR buyers:

"Video mode will probably be used as an extra selling point on cheaper SLRs, which is a very profitable and competitive end of the market. The key considerations will be the resolution and frame rate – if these are good enough, video capture mode will be welcomed by most DSLR users.”