The Nikkor Z 58mm f/0.95 S Noct is one of the biggest, most behemoth lenses available for Nikon's full-frame mirrorless cameras. According to Nikon, though, it could have been even bigger – with an increase in size "far beyond imagination".
Given that the Nikkor Z 58mm f/0.95 S Noct, at 153mm and 4 lb 6.6 oz / 2,000g, is already the most monstrous lens on the Nikon Z lens roadmap, how exactly could it be any beefier? The answer is simple: autofocus.
The Noct is, famously, a manual focus lens. And while it is certainly a challenge to nail precise focus – especially when shooting with the razor-thin depth of field at an f/0.95 aperture – the alternative was adding an autofocus mechanism that may have been unfeasibly big, unfeasibly slow and unfeasibly expensive.
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"Of course we have also studied AF, and driving the focus lens itself can be done," said Makoto Fujiwara, a designer for Nikon's Optical Engineering Division, in an interview with Chinese website Xitek (spotted by Mirrorless Rumors).
"But the action is quite slow, not as fast as manual operation. At the same time, the increase in size is far beyond imagination. It cannot be driven by the existing ultrasonic motor, and a larger actuator must be arranged outside the lens.
"Therefore, if you really want to achieve AF in the f/0.95 lens, this optical type will not work. You need to reduce the focus lens and use the internal focusing method. But using this method will result in a longer overall length, which means that peripheral components will also increase, and the lens will still be larger and heavier than it is now. Even if such a lens is made, even if the product is very special, it may not be established as a product, so we gave up AF."
So, does that mean an f/0.95 lens like the Noct can never be made with autofocus ? After all, the (admittedly much smaller) Fujfilm XF 50mm f/1.0 AF lens is set to be released later this year.
"We want to entrust future generations with the failure to do things this time as future dreams," said Fujiwara. Maybe for the Z mount successor, then…