So why use an expensive OLED panel when for decades a simple printed distance scale has done the job perfectly well?
It's because modern lenses have a short focus travel, which means that distance scales are compressed into just a few degrees of rotation on the zoom ring. If you're lucky, your lens will have a marker for infinity, 3m and 1m, but anything in between you'll have to guess at.
It's not a problem if you use autofocus, but if you want to focus manually and make the best use of depth of field – where focus distance is crucial – then most distance scales are hopelessly vague.
How it works
That's why Zeiss could genuinely be on to something. The OLED panel can report focus distances with far more accuracy than a printed scale… and it goes a whole step further. Either side of the focus distance, the panel displays the near and far limits of your depth of field – in other words, the nearest distance at which objects will still look sharp, and the farthest. It presumably gets this information from the camera body.
At a stroke, Zeiss is giving photographers the precise control over depth of field that's been missing from modern lenses for so long.
Price and availability
The new Batis lenses are designed exclusively for Sony's full-frame E-Mount A7-series compact system cameras. Interestingly, though, Zeiss is designing and marketing these lenses itself, whereas normally it makes lenses for Sony cameras in conjunction with Sony.
The Batis 25mm f/2 wideangle prime lens will cost US$1299 and the 85mm f/1.8 will cost US$1199. Both will be available from mid-July 2015. You can find out more at the Ziess Batis website.
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