PHOTOOG Photography writings by Olivier Giroux


Commentary: split-prism SLR focusing and the Leica rangefinder

I’m coming up on my first anniversary as a Zeiss ZF user. To this day, focusing errors are the most common reason I have to reject images. In keeping with tradition in photography, this is more of an issue when light is low – razor-thin depth-of-focus, dark and dull SLR viewfinders and noise-processing combine into the perfect storm against sharp focus.

Earlier this year I spent a few weeks with an FE-2 on loan, which I enjoyed very much. One of the old-school features I came to miss afterwards was the split-prism focusing screen. At the time I made a note to get a 3rd party screen for my D700 later. Now that I have a Brightscreen P795H installed, I have mixed feelings about the approach.

The split-prism screen makes some trade-offs compared to ubiquitous matte screens. For perpendicular detail with good contrast, the split-prism enables you focus faster and with higher accuracy. Conversely, for subjects that deviate from this ideal case it makes focusing more difficult and ultimately impossible. In that case, your only recourse is the camera’s phase-detect rangefinder.

Is it a bad deal? I’m not sure yet. It’s also the case that a dark SLR viewfinder invites reliance on the electronic rangefinder.

At the moment I’m experimenting with another classic on loan: the Leica M3. I haven’t put even a single roll of film through it yet but I can say with certainty that it is easier to focus the Leica rangefinder in low light. Overlap-focusing is fast and precise, so far meaning that small differences in distance on the lens’ scale are clearly visible as separate images in the rangefinder patch.

I suspect that there is truth in the superiority of rangefinders for manual focus.

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  1. I remember somebody once showing me how to use the split prism – it certainly makes focusing easier under good lighting. But I am not sure otherwise – I guess you would have to guesstimate the distance

  2. At this point I’m strongly considering going back to the clear matte, and maybe getting a viewfinder magnifier piece instead…

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