Godfrey
Well-known member
Um, in the optical viewfinder, why would you need anything more than the rangefinder spot to confirm focus?So nothing in the optical than for any focus confirm. Bummer ...
A rangefinder spot allows you to see what you are focusing on at the same time as whether it is in focus.
An indicator light requires you to look in two places to see what's in focus. An indicator light by itself can only tell you that something is in focus, you have to also target the thing you're focusing on to determine whether the indicator light is lit up.
I don't know that there's any added utility in that. Of course, the mechanics of in-focus indication means having some sort of phase detect or contrast detect focusing algorithm in place as well and I don't know how you'd do that with an optical-mechanical rangefinder apparatus that only knows where the focusing mount is turned to in order to align a prism to a particular point—the meaning of what it sees is up to your eye. Beyond that, you need a sensor or two in the viewfinder optical chain. In Live View mode, the main sensor could do the job, but the main sensor is covered by the shutter when not in Live View mode (unless they've gone to an open-shutter rest state, like with NEX and Micro-FourThirds).