AF and AF-D AF support on Z bodies

Leonard Shepherd · Aug 25, 2018

Short answer - never (even with a different adaptor) for the Z6 and Z7.

Why?

An in camera body AF motor is needed to drive screwdriver AF - the Z6 and Z7 do not have one.

Phase detect AF works out how much a subject is out of focus, instructs the AF motor how far to turn for correct focus, and thats about it for static subjects.

Whether contrast detect AF has the ability to calculate how far to exactly turn the focus motor from a single advance measurement may generate some heated debate.

This last detail is of no direct consequence for a body with no screwdriver AF drive.

--
Leonard Shepherd
In lots of ways good photography is much more about how equipment is used rather than the equipment being used.

beatboxa · Aug 25, 2018

Leonard Shepherd said:
Short answer - never (even with a different adaptor) for the Z6 and Z7.

Why?

An in camera body AF motor is needed to drive screwdriver AF - the Z6 and Z7 do not have one.

Phase detect AF works out how much a subject is out of focus, instructs the AF motor how far to turn for correct focus, and thats about it for static subjects.

Whether contrast detect AF has the ability to calculate how far to exactly turn the focus motor from a single advance measurement may generate some heated debate.

This last detail is of no direct consequence for a body with no screwdriver AF drive.

An "in-body AF motor" is not needed. Any motor external to the lens works, including a motor in the adapter. So in-body motor is not required--doesn't matter if Z6 & Z7 don't have them.

The Z6 & Z7 both have PDAF as well as CDAF--and as we've seen in DSLRs in live view, these screwdriver lenses can autofocus with CDAF as well. Because it turns out, they don't require just a single instruction one time. There are plenty of ways to make this a continuous feedback loop, such as having a series of instructions.

And this can also be dependent on how "aware" the Z6 & Z7 are of older focusing methods--or whether this happens in the adapter. In other words, Nikon may have native/legacy AF logic built into the cameras. Or Nikon may be translating AF within the adapter to some new logic. But there is no evidence of either yet. Anecdotally, all we know is that the adapted AF works well.

So the short answer is: "certainly possible."

This is different than "will it work exactly the same as it does in the DSLRs?" Then again, this same question applies to AF-S and other lens types as well.

mick232 · Aug 25, 2018

Leonard Shepherd said:
Short answer - never (even with a different adaptor) for the Z6 and Z7.

Why?

An in camera body AF motor is needed to drive screwdriver AF - the Z6 and Z7 do not have one.

Phase detect AF works out how much a subject is out of focus, instructs the AF motor how far to turn for correct focus, and thats about it for static subjects.

Whether contrast detect AF has the ability to calculate how far to exactly turn the focus motor from a single advance measurement may generate some heated debate.

This last detail is of no direct consequence for a body with no screwdriver AF drive.

I am not saying it's going to happen or very likely. But what is the reason the AF motor can't be in the adapter? The Sony LA-EA4 is built that way.

Leonard Shepherd · Aug 25, 2018

mick232 said:
I am not saying it's going to happen or very likely. But what is the reason the AF motor can't be in the adapter? The Sony LA-EA4 is built that way.

Whether phase detect assist on ML bodies works exactly the same way as the phase detect sensors in the base of a Nikon DSLR is not know. It probably does not as there seems no sub mirror system to direct light to the AF sensors in the base of Nikon DSLR's.

A motor could be in the adaptor but it would still need electrical contacts to receive the AF instructions as to which way and how far to turn.

On screwdriver AF bodies no lens/body electric contacts are used during screwdriver AF.

Such a system might slow up other functions. The electric information transfer between lens and body is usually a serial link where data travels sequentially down a single wire with a digital clock timing the data transfer timing sequence between transmitter and receiver.

No-one as yet outside of Nikon is likely to have worked out the signalling detail used in the Z mount 11 electrical contact points works. The camera body would need to be able to tell an in converter motor when to start and stop and which way to turn using the 11 electrical contacts of the Z mount system.

Whether it would be "worth the cost" to photographers when screwdriver AF is usually not the fastest available AF and very precise manual focus is available on the rear monitor is another topic.

There is an ideal body for pre AF, AF and AF-D lenses with the Df.

NCB · Aug 25, 2018

Depends whether you mean support for autofocus or support for such lenses. The latter's OK if you don't mind focusing manually.

But I'd agree, a Df will solve the problem.

mick232 · Aug 25, 2018

Leonard Shepherd said:
mick232 said:

I am not saying it's going to happen or very likely. But what is the reason the AF motor can't be in the adapter? The Sony LA-EA4 is built that way.

Click to expand...

Whether phase detect assist on ML bodies works exactly the same way as the phase detect sensors in the base of a Nikon DSLR is not know. It probably does not as there seems no sub mirror system to direct light to the AF sensors in the base of Nikon DSLR's.

Correct. But that doesn't rule out an adapter that contains a semi-transparent mirror that diverts some light to PDAF sensors in the adapter.

Leonard Shepherd said:
A motor could be in the adaptor but it would still need electrical contacts to receive the AF instructions as to which way and how far to turn.

No. The motor doesn't need to know how far to turn. It only needs to know if it should be off or on, and when turned on in what direction to spin. For that it needs the same electrical contacts as a motor in the body.

Leonard Shepherd said:
On screwdriver AF bodies no lens/body electric contacts are used during screwdriver AF.

Here, we are talking about the Z6 and Z7. If Nikon wanted to have backwards compatibility with screwdriver AF, there isn't anything that prevents them from sending AF signals through the contacts in the Z mount during screwdriver AF.

Leonard Shepherd said:
Such a system might slow up other functions. The electric information transfer between lens and body is usually a serial link where data travels sequentially down a single wire with a digital clock timing the data transfer timing sequence between transmitter and receiver.

Very unlikely. The mechanical auto-focus operation is super-slow compared to any electronic processing. For the camera, it takes ages from the moment it wants the lens to start moving until it wants it to stop moving. This will not consume any significant portion of the link's bandwidth.

Leonard Shepherd said:
No-one as yet outside of Nikon is likely to have worked out the signalling detail used in the Z mount 11 electrical contact points works. The camera body would need to be able to tell an in converter motor when to start and stop and which way to turn using the 11 electrical contacts of the Z mount system.

That's right and not impossible. It's also not the only option. The adapter itself could make these decisions if it has its own PDAF sensors.

Leonard Shepherd said:
Whether it would be "worth the cost" to photographers when screwdriver AF is usually not the fastest available AF and very precise manual focus is available on the rear monitor is another topic.

100% agreed.

Leonard Shepherd said:
There is an ideal body for pre AF, AF and AF-D lenses with the Df.

Mackiesback · Aug 25, 2018

Leonard Shepherd said:
mick232 said:

I am not saying it's going to happen or very likely. But what is the reason the AF motor can't be in the adapter? The Sony LA-EA4 is built that way.

Click to expand...

Whether phase detect assist on ML bodies works exactly the same way as the phase detect sensors in the base of a Nikon DSLR is not know. It probably does not as there seems no sub mirror system to direct light to the AF sensors in the base of Nikon DSLR's.

A motor could be in the adaptor but it would still need electrical contacts to receive the AF instructions as to which way and how far to turn.

On screwdriver AF bodies no lens/body electric contacts are used during screwdriver AF.

Such a system might slow up other functions. The electric information transfer between lens and body is usually a serial link where data travels sequentially down a single wire with a digital clock timing the data transfer timing sequence between transmitter and receiver.

No-one as yet outside of Nikon is likely to have worked out the signalling detail used in the Z mount 11 electrical contact points works. The camera body would need to be able to tell an in converter motor when to start and stop and which way to turn using the 11 electrical contacts of the Z mount system.

Whether it would be "worth the cost" to photographers when screwdriver AF is usually not the fastest available AF and very precise manual focus is available on the rear monitor is another topic.

There is an ideal body for pre AF, AF and AF-D lenses with the Df.

The only advantage the Df has over any FF prosumer and pro cameras is the ability to adapt to pre ai lenses. Other than that the Df holds no advantage for backwards compatibility.

gabgon · Aug 25, 2018

I own nine f/2.8 and f/1.4 AF-D lenses and am very disappointed that they will not work on the new ML Z bodies unless I want to use them in manual focus.

I had been looking into a Sony a7 ML body, but was turned off by losing the auto focus on my D lenses. Turns out they won't auto focus on a Nikon Z body anyway. So what's stopping me from just buying a Sony now?

While I wish Nikon wouldn't follow the same path as Olympus did and discontinue their DSLRS once they believe their ML performance had caught up with their DSLRS, I know they will. That's where all camera systems are headed: mirrorless.

There's no reason why Nikon couldn't have placed a focus motor in their adapter. It would have kept backwards compatibility with D lenses and kept everyone happy. For those of us with a decent investment in D lenses, it's disappointing. For Nikon, it should also be disappointing as there's no reason for anyone having to re-buy lenses not to do so along with a ML body, but from one of Nikon's competitors instead.

Leonard Shepherd · Aug 26, 2018

Mackiesback said:
The only advantage the Df has over any FF prosumer and pro cameras is the ability to adapt to pre ai lenses.

For some Nikon photographers this is a huge advantage.

Leonard Shepherd · Aug 26, 2018

mick232 said:
that doesn't rule out an adapter that contains a semi-transparent mirror that diverts some light to PDAF sensors in the adapter.

This seems a very expensive to make work around with some loss of light transmission.

mick232 said:
mick232 said:

A motor could be in the adaptor but it would still need electrical contacts to receive the AF instructions as to which way and how far to turn.

Click to expand...

No. The motor doesn't need to know how far to turn. It only needs to know if it should be off or on, and when turned on in what direction to spin. For that it needs the same electrical contacts as a motor in the body.

This depends on whether a screwdriver AF lens can be controlled by AF-s or P lens signalling.

beatboxa · Aug 26, 2018

Leonard Shepherd said:
Mackiesback said:

The only advantage the Df has over any FF prosumer and pro cameras is the ability to adapt to pre ai lenses.

Click to expand...

For some Nikon photographers this is a huge advantage.

Interestingly, some of Nikons lowest end cameras (D7500 + D5xxx & below) can also mount pre-AI lenses.

But I don't think the Df is "ideal" for manual lenses. It just happens to let pre-AI lenses mount.

Mirrorless / EVF, is far better for manual lenses than today's DSLRs, which lack appropriate MF aids just as split-prism focussing screens of the past.

sandy b · Aug 26, 2018

While they would not AF, wouldn't they meter better on the Nikon? Just spitballing.

Mackiesback · Aug 27, 2018

beatboxa said:
Leonard Shepherd said:

Mackiesback said:

The only advantage the Df has over any FF prosumer and pro cameras is the ability to adapt to pre ai lenses.

Click to expand...

For some Nikon photographers this is a huge advantage.

Click to expand...

Interestingly, some of Nikons lowest end cameras (D7500 + D5xxx & below) can also mount pre-AI lenses.

But I don't think the Df is "ideal" for manual lenses. It just happens to let pre-AI lenses mount.

Mirrorless / EVF, is far better for manual lenses than today's DSLRs, which lack appropriate MF aids just as split-prism focussing screens of the past.

Before ML, it was about as "ideal" in digital that Nikon had. Since it was marketed towards the MF crowd among others, (how could you not with the flipping tab?), it is a puzzlement why Nikon didn't include a viewfinder better suited towards MF. It's little things like that that have people questioning Nikon's sanity, and rightly so. We are seeing it this week with the dual slot overload.

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