# D5100 + 28-70mm 2.8 = No autofocus?



## EchoingWhisper (Apr 14, 2012)

This is weird. My D5100 is supposed to be able to auto focus with all AF-S lenses, including the AF-S 28-70mm f/2.8D. For some reason, I borrowed my friends 28-70, I couldn't autofocus with it. All focal length were okay except the ones near 70mm. It focused well with his D1x but on my D5100, it hunts and hunts and hunts and never stops. I wonder if this is an issue with my camera. I thought it was the problem with the side focus points but I tried the middle one but it doesn't work either. I have a full frame lens and it worked well. Is it the D that is causing the problem? Seems unlikely. Any help?


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## Kerbouchard (Apr 14, 2012)

The D just mean's it communicates distance to your camera to help with flash exposure.  Nothing to do with focus.

My guess, it wasn't seated completely or the contacts on either your camera or the lens are a bit dirty.  Probably both.

Quick and easy solution is to unmount it and remount it making sure it clicks.  If that doesn't work, you can take a lint free cloth and wipe off the contacts.

That's about the only thing I can think of that would explain both the camera and lens working in other situations, but just not together.


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## EchoingWhisper (Apr 14, 2012)

Kerbouchard said:


> The D just mean's it communicates distance to your camera to help with flash exposure.  Nothing to do with focus.
> 
> My guess, it wasn't seated completely or the contacts on either your camera or the lens are a bit dirty.  Probably both.
> 
> ...



Hmm, took it off and on but it still didn't work just now. Maybe the contacts (most likely mine, but maybe his too, cause' its an old lens) are dirty. Will try it the next time.


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## Kerbouchard (Apr 14, 2012)

The reason I say the contacts are if both are a bit dirty, it could interfere with the connection, where in other situations, if you are mounting slightly dirty contacts to clean contacts, it might not intefere.

Like I said, I would take a lint free piece of cloth(an old t-shirt works fine) and clean both sets of contacts.  If that doesn't help, you might try and see if you have the latest firmware for your camera.  Could be an issue Nikon took care of during a revision.


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## EchoingWhisper (Apr 14, 2012)

Kerbouchard said:


> The reason I say the contacts are if both are a bit dirty, it could interfere with the connection, where in other situations, if you are mounting slightly dirty contacts to clean contacts, it might not intefere.
> 
> Like I said, I would take a lint free piece of cloth(an old t-shirt works fine) and clean both sets of contacts.  If that doesn't help, you might try and see if you have the latest firmware for your camera.  Could be an issue Nikon took care of during a revision.



Thanks! Will try it.


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## djacobox372 (Apr 16, 2012)

Nare u sure u have a af-s lens? Most tamron 28-75mm f2.8 are af lenses.


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## EchoingWhisper (Apr 17, 2012)

It's a Nikkor 28-70mm.


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## EchoingWhisper (Apr 17, 2012)

Amazon.com: Nikon 28-70mm f/2.8D ED-IF AF-S Zoom Nikkor Lens for Nikon Digital SLR Cameras: Camera & Photo


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## dayvidtang (Apr 17, 2012)

You have a D lens, and the D5100 model does not have a built in autofocus motor. You need a lens that has a built in AF or ends with a G.
For example:
Amazon.com: Nikon 24-70mm f/2.8G ED AF-S Nikkor Wide Angle Zoom Lens: Electronics


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## MTVision (Apr 17, 2012)

dayvidtang said:
			
		

> You have a D lens, and the D5100 model does not have a built in autofocus motor. You need a lens that has a built in AF or ends with a G.
> For example:
> Amazon.com: Nikon 24-70mm f/2.8G ED AF-S Nikkor Wide Angle Zoom Lens: Electronics



The lens he's taking about has a built in af motor - or at least that's what the af-s means. I thought the D meant that the lens has the electronics to pass distance information to the camera not that it had anything to do with AF

http://www.kenrockwell.com/nikon/2870afs.htm


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## dayvidtang (Apr 18, 2012)

Oh whoops, I mixed it up D: Yeah, you're correct; it probably is the connectors.


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## EchoingWhisper (Apr 18, 2012)

All G lenses are also D lenses.


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## KmH (Apr 18, 2012)

The G only means there is no aperture ring on the lens. Most D lenses have an aperture ring.

The D means the lens is a CPU lens that communicates distance information to the camera AF module, and other systems as needed. The AF module uses that distance info to back and forth bracket to focus lock. Of course D lenses are auto focused by the screw-drive motor system in the camera body, while AF-S lenses are auto focused with the stepper motor in the lens.

The way AF-D and AF-S G lenses are focused by the AF module electronics in the camera is also different, which is why AF-S lenses usually are able to achieve focus faster than AF-D lenses. AF-S lenses don't have to do as much back and forth focus refinement as AF-D lenses do.

If you're not sure if a lens is an AF-S or an AF-D, you can tell by looking at the lens mount. A D lens has a slot in the mount the screw-drive system connects to so it can drive the lens focus mechanism. An AF-S lens lacks the screw-drive system connection slot, though there is a blank recess for the screw-drive to sit in.



> G-Type NIKKOR Lens G-type NIKKOR lenses have no aperture control ring and are intended for use on Nikon D-SLRs that allow the lens aperture to be adjusted via the camera's command dial.





> D-Type NIKKOR Lens
> A NIKKOR lens that sends distance information to the microcomputer of a dedicated Nikon camera. D-type lenses can be distinguished by a model name in which the letter D follows the maximum f/number.


 Photography Glossary for all your photography questions


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## IByte (Apr 18, 2012)

KmH said:
			
		

> The G only means there is no aperture ring on the lens. Most D lenses have an aperture ring.
> 
> The D means the lens is a CPU lens that communicates distance information to the camera AF module, and other systems as needed. The AF module uses that distance info to back and forth bracket to focus lock. Of course D lenses are auto focused by the screw-drive motor system in the camera body, while AF-S lenses are auto focused with the stepper motor in the lens.
> 
> ...



Sooo the D lenses works best with camera bodies with an internal motor, and G lenses are for (general purposes) work with camera bodies with no internal motors?  Or am I being to simplistic?


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## EchoingWhisper (Apr 18, 2012)

Hmmm, odd. This lens is both a AF-D and AF-S lens. lol


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## KmH (Apr 18, 2012)

Yep. Nikon made a few AF-S D lenses, like the AF-S 80-200 mm f/2.8D. So AF-S D lenses have an internal auto focus motor, and an aperture ring. 

Nikon quit making the AF-S 28-70 mm f/2.8D in 2007. The much more expensive AF-S 24-70 mm f/2.8G took it's place.


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