Extended Depth of Field (EDoF) cameras, also known as Full Focus, have enabled Nokia to make ever thinner smartphones. Rather than relying on the larger actuating auto-focus lens system to produce a sharp image, EDoF exploits image processing algorithms to create an image that is universally sharp. The trade off here is that capturing fine details (like text) is often not possible, and there is a minimum focal distance of 50cm. Well, Jade Bryan over at SymbianWorld.org has come up with a method to get around this limitation, and like all the best ideas, it is remarkably simple. Read on to find out more.

Jade's method is to simply use a magnifying glass! Then, the minimum focal distance of an EDoF camera is effectively reduced by external optical means. In the post at Symbian World, there are some example photos of flowers as a demonstration (see below), and the results are remarkably good. Upon closer inspection, what can be seen is that the depth of field is reduced in line with the characteristics of the magnifying glass (which will be of little surprise to anyone with an appreciation of optics). This isn't a problem though, as the whole point of macro photography is to only capture the nearest objects!

Jade also says that this method can be applied to enhance the N8's macro mode, and presumably any other auto-focus camera phone.

What isn't reported in the post is whether this magnifying glass trick can be used to help EDoF cameras capture documents. Admittedly, this is a specialised use case, but there are some people out there (myself included) who have dumped their flatbed scanners in favour of using their digital cameras. Nokia units like the N97 and E72, etc, are quite capable of this, but because of the fine fuzziness in EDoF image processing, capturing documents has been near impossible on phones like the E55 and C7.

With that in mind, I shall be procuring a magnifying glass for myself to see how well I can reproduce Jade's results with my C7!

"Magnifying Glass plus Nokia C7 (full focus) combo
The only key to somehow reduced the focusing distance is to magnify your subject. Of course by using a magnifying glass that you could purchase in school supply stores or hardware tools section in a mall. For just a couple of quid you could have a fine clear magnifying glass. And the play is to attached by rubber band or manually hold the magnifier and the phone itself.

For the product of this  combination you would get up to 50% less of the minimum full focus distance (10-36cm from 50cm min) required by Full Focus camera modules on these Nokia devices. You just need a little effort by adjusting the best position on getting closer focus to the subject. And since you are on the magnifying glass the flash will be not suitable for this event."

David Gilson for All About Symbian, 21st December 2010