Digital Frameline Viewfinder

In an ordinary SLR or dSLR, the light comes in through the lens and is reflected off a mirror in the lightpath (hence the 'reflex' in SLR). The light then gets corrected left-right by being bounced off the sides of a pentaprism (or in the case of a slightly less than recent Olympus dSLR, a 'porroprism', which is simply a mirror arrangement instead of a solid chunk of glass, with the attendant disadvantages of a seemingly smaller image, and quite noticeably darker too*). The mirror mechanically gets out of the way in time for the exposure.

Rangefinder cameras avoid this mechanical complexity by offering a similar view to your lens, but one which is in fact separate, distinct, and from a slightly different point of view. The latter aspect isn't really so much of a problem - most rangefinders show parallax correction markings in the viewfinder. Sophisticated rangefinders even show an attempt at in-focus/out-of-focus indication, and some even show the action of zooming (my old Contax TVS used to zoom the viewfinder to match the angle of view of the lens).

Modern cameras could make use of an interesting form of neuro-optical technology from about 1952, manifested in a device called the Voigtlander Kontur viewfinder. This is simply a viewfinder that slides into the cameras cold shoe, which in this case, entirely blocks out the view (most viewfinders actually show the view - this one doesn't - it's blacked out). All that remains is a bright outline in the shape of the rectangle representing the border of the frame. The idea is that you look through the Kontur with one eye, and the scene itself with the other eye and your brain composites the frameline image onto the natural image of the other eye.

It occurred to me that this technology should be revived, and with the high degree of technological sophistry in modern dSLRs, a rangefinder version of a body should be able to be made, that accepts modern lenses and their relevant zoom information. The viewfinder can present focus indication in the form of a coloured light, much as is the case today, but the viewfinder doesn't present the scene from through the lens - it simply superimposes a frameline image against your other eyes scene image.

Knowing the actual lens specifications and current zoom setting (from the lens electronic contacts in the mount), it could 'zoom' the frameline, which after all, could now easily be synthesized by a tiny but high- resolution LCD in the viewfinder itself. Further information could be made to be 'suspended' within the field of view. Zoom the lens, and the superimposed rectangle grows bigger or smaller against your eyes vision, showing you how much of the scene is being taken. The only disadvantage would be at extreme telephoto ends of extremely long lenses - but they're typically not the sort of lens you buy a rangefinder to use on anyway. This is a disadvantage only in that the rectangle grows bigger or smaller, unlike the view through the pentaprism in which the rectangle remains a constant size, and the view simply gives the impression of being more or less 'magnified'.

The advantages are: silent(er) operation; simpler, potentially more reliable construction; significantly smaller camera body; vastly brighter 'viewfinder' (in that it is simply what your unaided eye is seeing); peripheral vision available; magic technical superimposed graphic imagery appearing over what seems to be your unaided eyes vision.

So, to sum up, this electronic viewfinder doesn't actually show any picture image, it simply shows instrumentation imagery that becomes composited in the brain with your other eyes image of the scene.

* (I have a big boxy porrofinder for my Mamiya C330 TLR - it too is almost unusably dark).