What's the difference?

[Nikonoff]

Hi all, found these two lenses on the Kogan site and not sure what the difference is.

Nikon AF-P DX 18-55mm f/3.5-5.6G VR Lens and this lens Nikon AF-S DX 18-55mm f/3.5-5.6 VR II Lens

p.s. these are not links, but in hindsight probably should've been:o

[J.davis]

I believe the P model is for the newer Nikon bodies, but will still work on some older bodies.
Different AF Systems I think.

[arthurking83]

AF-P won't work with your D90! :(

Like John says, it's the way(or type of) focus motor system in the lens.

Long answer:

Think of a typical standard motor type, like in a fan, that just spins when power is applied. If you cut the power while the motor spins, it doesn't stop dead immediately(like the fan), but it slows down due to momentum.
If a lens had this type of focus motor in it(and some did I think), it then needs a brake mechanism to stop it when it reached it's focus spot. Inefficient.

Note the AF-S part of the name in the other lens.
This is Nikon's version of an ultrasonic driven focus motor. Instead of a normal dc type motor that doesn't understand where too start stop in the rotation process, an ultrasonic motor 'knows' it's position and 'knows' how many steps are required to get to any other position.

(** note that I use the term 'knows' as an easier way to understand the process, an ultrasonic motor is still dumb, but the lens has an internal CPU and is the actual brains and tells this ultrasonic motor how many steps required to move to another position ** )
These motor types are very fast to operate tho, and can give a lot of torque(turning force) for the amount of power they need to run. In this design, the CPU in the lens sends pulses of power(waves of power) to the motor to turn it in small steps but very rapidly.
SO you get speed and accuracy. As the lens approaches the point where the image is getting sharp, the PCU then tells the lens to stop, and (usually) a correction pulse of power to come back a very slight amount too. But because it doesn't freely turn, like the DC motor does in the fan) it can estimate a very close position for the lens to stop. These motor types are expensive to build tho (compared to DC motors).

AF-P is a different motor type again, and is called a stepper motor.
These motor types can be setup to know where they are in their rotation, and can be given exact command to move to an exact (and very precise) new position.
if they had a lot more torque then they currently do, they're the perfect AF motor type.

The advantage of stepper motors is the ability to be told to move to a new position exactly, whereas the ultrasonic motor is send the power to move position(continuously) until the CPU determines that any position during the time the USM motor is moving is the best spot for focus. It may very slightly overshoot the mark, so it may need the power command to move back a little. Stepper motors can move to an exact position.
it's easier to make stepper motors move in more precise steps(as a random example: say 0.001° for a stepper motor as opposed to 0.01° for an ultrasonic motor.
So the main advantage of a stepper motor over a USM type is more accuracy and awareness of it's position and the position it needs to be set too.

if you've ever seen a printer move it's internal print nozzle contraption you're seeing a stepper motor at work. They can move very quickly from one spot to another and stop instantly, with a single command from the CPU.
... rather than the CPU sending power to a USM motor until it reached a spot, then the CPU determined that the spot it got too it too far and needs to come back.
If a printer used USM motors instead of steppers, then the print would be a random mess of ink dots, or the printing process would take a lot longer to happen.

Stepper motors are very good for video AF due to the accuracy, and that a camera can guesstimate where it needs to be set too to achieve good focus(ie. the accuracy part of the process).

More long winded ramblings, but could be of interest to Nikon owners!!

AF-P lenses are the type of lens you need to be sure you know what you're buying .... like the old days when Nikon first brought out the D40(then the D60 ... and D3000 and D5000) type cameras that can only autofocus with AF-S type lenses.
AF-D lenses can't AF on those camera bodies as they don' thave the focus motor in the body that's required for AF.
AF-P tho is a strange beast that Nikon only recently introduced.
There are very few cameras that they fully work with, and that list of camera bodies is the strange part. eg. D5500 can fully work an AF-P lens, but the more expensive D810 can't. Note that a D5500 may need a firmware update for it to fully work.
All new bodies work tho.
The main issue with the cameras that only work partly with AF-P lenses is that you lose focus if the cameras meter does it's normal auto off(about 6sec on average by default on Nikon cameras).
That is, you may be doing landscapes/architectural, and set yourself a specific focus distance, but may wait for something before you take your shot(s).
In the pre AF-P days, focus never reset itself. Where you last focused, focus stayed.
But because these new stepper motor lenses have focus motors that know where they are, on some of these partly compatible cameras, the camera can't send the lens the required command to know where it is once the meter powers off automatically.
That is, they AF OK, but every time the meter turns off, they lose focus. May not be annoying to some, I view it that it would be annoying all the time!

Nikon have a compatibility list, but it's not easy to find(read that as in: they've made this vital info close to impossible to find! :rolleyes:)

But here is something of the sort:


The number of cameras compatible with both lenses is limited. Even for compatible cameras, firmware update may be required*. Fully compatible models: D7500, D5600, D5500, D5300*, D3400, D3300*, D500 and later models

Compatible models with limited functions: D5, D810 series, Df, D750, D7200, D7100, D5200, Nikon 1 series with the FT1

Incompatible models: D4 series, D3 series, D2 series, D1 series, D800 series, D700, D610, D600, D300 series, D200, D100, D7000, D5100, D5000, D90, D80, D70 series, D3200, D3100, D3000, D60, D50, D40 series, film cameras

I think Nikon currently have 4/5 AF-P lens types in their list.
The other lenses are the 10-20 Dx AF-P : 18-55 Dx AF-P : 70-300 Dx AF-P (2 models) : 70-300 AF-P.

The last issue with the consumer dx model lenses is if they are VR models too. I don't think any of the Dx VR lenses have a VR on off switch! :confused013
Not only is this the second stupidest design choice of all time ... ever, it adds to the compatibility list above.
That is, you can't turn VR off if you don't have a camera that is fully compatible. The option to turn VR on/off is now an in camera item, not on lens like the old days.
I think the firmware update for those listed cameras adds the VR option in the camera menu.
The Fx version of the 70-300 f/4.5-5.6 VR does have the VR on off switch, so isn't affected in this way.

[Nikonoff]

AF-P won't work with your D90! :(

Like John says, it's the way(or type of) focus motor system in the lens.

The last issue with the consumer dx model lenses is if they are VR models too. I don't think any of the Dx VR lenses have a VR on off switch! :confused013
Not only is this the second stupidest design choice of all time ... ever, it adds to the compatibility list above.
That is, you can't turn VR off if you don't have a camera that is fully compatible. The option to turn VR on/off is now an in camera item, not on lens like the old days.
I think the firmware update for those listed cameras adds the VR option in the camera menu.
The Fx version of the 70-300 f/4.5-5.6 VR does have the VR on off switch, so isn't affected in this way.

Arthur a simple thanks seems grossly inadequate, but I can't think of a clever superlative, so thanks for the very interesting and informative read.
Regarding the DX lenses with VR they do indeed have on/off switches, when I bought mine it came as a twin lens kit, both DX VR. I find the 18 - 55 to be particularly good for a budget lens and since my daughter sort of claimed it I find myself looking to acquire another one hence the initial query. Thanks for clarifying Arthur, I'm going to copy/paste you reply into a word doc for future reference.

[arthurking83]

.....
Regarding the DX lenses with VR they do indeed have on/off switches ....

You've misread my comment.
These new AF-P Dx lenses, don't have the VR on off switch.
Up until those new ones, you're right they do have them, and all VR lenses Nikon have made had them.
This is another change that Nikon has stuffed up..
With these VR AF-P lenses without the VR switch, you can only turn the VR on/off via the camera's menu.

The only AF-P lens with VR that has the lens switch is the non Dx 70-300 AF-P f/4.5-5.6 lens model.

Can't help but think .. are Nikon so hard up for profitability that they really need to save a few cents on a couple of hundred dollar lens product? Just add a little extra for the switch which they do for the VR mechanisms anyhow! :confused013

So this is why some cameras aren't fully compatible with those new lens types either. And others are fully compatible with a firmware upgrade too. The firmware adds the VR on/off item in the camera menu.
I think there are a few cameras that are affected in this manner, and when updating the firmware subsequently become fully compatible.

Hope that clears up the misunderstanding.

[Steve Axford]

Arthur, I suspect that the switch is going to cost more than a few cents. Remember, it is the switch, the sealing around the switch, the wiring, the installation, etc. Having no switch is easier and simpler and cheaper. It is hard enough to maintain upward compatibility let alone downward compatibility as well. Anyway, does it matter a lot? Does the VR being on effect many photos adversely?

[arthurking83]

.... Does the VR being on effect many photos adversely?

When shooting on a tripod it can, for sure.

I think their theory is that if people are buying such a product, it's more likely to be with a more modern(lower end) type product, so the compatibility is almost a non issue.

That is, someone that purchased a D3000 back in 2008 is less likely to purchase an 18-55 AF-P lens, even if that's simply for the purpose of replacing a broken old 18-55AF-S kit lens.
The camera is now quite old, has probably served a useful purpose over the last 10 years and it may be time to update(to the latest D3xxx + kit lens) or something else entirely.

The major issue is that Nikon haven't made it easy for people to know, or understand .. if the new AF-P type lens(es) will work on their camera!
... ie. as the OP has proved.

The inner workings of the two different AF systems themselves aren't important ... but the point that the AF-P lens won't work on the D90(at all) would have been sufficient in the ad material.
Note tho that they do have a very limited list of 'compatible' models deep down in the specs list.

- - - Updated - - -

ps. there's a bit of speculation going around that the reason for the AF-P lens intro is that this is a precursor to Nikon's introduction of a mirrorless camera.
Stepper motor systems work much better on mirrorless AF systems(both PD and CD af) on their sensors, due to the previously mentioned ability to know where the lens currently is focused at, and where it needs to be to be focused 'better'.
Makes for faster af for on sensor AF(ie. mirrorless) designs.

And I suspect that for use in an adapted mount system, the stepper motor type will translate info from camera to lens more accurately to provide faster more accurate AF too.

That is, the current AF-S type and older lenses, won't be as fast or accurate on a mirrorless camera via an adapter even tho they some of these AF-S lens types are blisteringly fast at AF.(eg. the 70-200/2.8 lens trio).
Mount them via an adapter to a mirrorless camera and they'll lose this advantage. Stepper motor focus drives alleviate this issue.

As for the price of the A/M - VR On/Off switch .. they tend to retail for about $20 or so(in the US). By my estimates, I'd say that they probably cost Nikon at about $1 to have manufactured ... possibly 0.99c :p
This is based on estimated costs of shipping/warehousing/ROI and Nikon's need to profit massively on their parts supplies. ;)

[Steve Axford]

Interesting comment of the step motors. I know that some older Canon lenses don't focus at all on the Sony A7R2, the newer ones do, but maybe not as well.
As I said, I can understand Nikon's attitude with this sort of thing. It can be very expensive to keep downward compatibility and they probably have an edict that their engineers don't need to worry about certain back level cameras. That would mean they don't even need to document any changes for those back levelled cameras, though they probably should say if they've done that - something like "results are unpredictable when used with xxx". But, documentation isn't cheap and manufacturers will avoid it if possible.