manual focus ring

WHy does nikon use a manual focus ring that doesnt stop when the focus scale stops?

WHy does nikon use a manual focus ring that doesnt stop when the focus scale stops?

Exactly which lenses are you talking about?

The focus-by-wire rings on Z lenses has many functions and no hard stop - and the way it is implemented doesn't really differ from other mirrorless camera brands.

My MF and AF Nikkors all have infinity hard stop.

AF-s micro 85mm

 

af-p 70-300 1:4.5-5.6E vr ed

 

manual ring just spins no matter what.

 

the micro the infinity does stop about on the far left end of the infinity loop, but the lens elements DO go out of focus if you keep moving it.

OK. I don't know these lenses as I never ventured into Nikon DSLRs - My relationship with Nikon MF and AF ended with a X90 (N90) started again with the Z system.

 

If there is a scale on the Micro-Nikkor, I'd expect it to have a hardstop at infinity, and if not I would assume it would need adjustment. Some with actual experience with the lens can hopefully clarify.

 

As for spinning freely on the zoom, a quick Google image search seems to indicate it is a focus-by-wire lens: welcome to the brave new world.

Edited March 31, 2022 by NHSN

AF-S lenses have no hard manual focus stop. That seems to extend to AF-P lenses and Z lenses.

I am not sure exactly what the mechanical coupling is between the focusing group and the manual focus ring, but I believe there to be a brush involved. This explains how it can run into the limit and you can still turn the ring (you can feel the limit however).

Many lenses, both manual and AF, focus past the infinity mark for a variety of reasons. It guarantees the ability to focus at infinity despite manufacturing tolerances and temperature effects. In part, it is in deference to the complexity of internal focusing, compared to a simple focusing helix.

 

AFS lenses use a stepping motor with an inverted rotor design. The rotor is connected directly to the focus mechanism, and the ring to the stator. In manual mode, the rotor and stator are locked together. Most modern lenses use linear motors for focusing and optical encoders on the focusing ring to sense its position and/or amount rotation. The latter technology is more common in cheaper lenses, and focusing is consequently free-wheeling and velocity dependent.

Also "Infinity" is just a marker of the maximum distance where maybe can be focussed on with the lens in question.

In reality "Infinity" cannot be measured, so it cannot be focussed on either ..

It can, in fact.

Also "Infinity" is just a marker of the maximum distance where maybe can be focussed on with the lens in question.

In reality "Infinity" cannot be measured, so it cannot be focussed on either ..

Also "Infinity" is just a marker of the maximum distance where maybe can be focussed on with the lens in question.

In reality "Infinity" cannot be measured, so it cannot be focussed on either ..

A star is a convenient target at an "infinite" distance, or its earthly emulation called a "collimator."

The AF-S and I guess it's the same for the AF-P which allows you to manual focus when the lens is in AF mode. Thus the focusing ring is designed to slip so you are not fighting with the motor. When the focus scale stops the focusing ring isn't changing the focus. It slips and doesn't turn anything.

This is a different thing from what Ed said that AF lenses can focus past infinity which they do.

It was always my understanding that modern lenses avoid the hard stop at infinity as a way to compensate for changes in temperature/humidity. As the lens shrinks or expands at a miniscule level, the ability to focus past infinity allows for breathing room. With a hard stop, it might be possible to get in a situation where you couldn't focus all the way to infinity.

My Zeiss Batis lenses (for Sony) focus past infinity and have a focus ring which rotates without stops. It has an OLED display of the focal distance which stops tallying just beyond infinity. I found, when shooting starry sky photos, that images were sharp at the point the infinity mark turned on or off. This proved useful under really dark skies, past astronomical twilight, when the EVF became a swirling mass of noise.

 

There is a mathematical reason related to automatic focusing, where a hard stop constitutes a step change in system gain, making it hard for the focusing to settle cleanly at the infinity point. The ad hoc solution is to add a dead band, which is inconsistent with critical focusing.

 

I don't think thermal expansion is a significant factor in a small lens like the Batis. Loxia lenses are similar in size but completely manual. They have a hard infinity stop which is accurate for starry skies photography.

The AF-P lenses don't even have an actual mechanical connection between the focusing ring and the elements. It's essentially "drive by wire". When you turn the focus ring the lens is still using the internal motor to move the elements. This is not the case with the AF-S lenses.

It was always my understanding that modern lenses avoid the hard stop at infinity as a way to compensate for changes in temperature/humidity. As the lens shrinks or expands at a miniscule level, the ability to focus past infinity allows for breathing room. With a hard stop, it might be possible to get in a situation where you couldn't focus all the way to infinity.

 

This is what I was told, mostly about telephoto lenses, 60 years ago.

Many lenses, both manual and AF, focus past the infinity mark for a variety of reasons. It guarantees the ability to focus at infinity despite .... temperature effects.

 

This is an important reason, especially with large and long lenses.....