Configuring AF-S 18-55mm VR lens

JockTheCoalman

Hello. I love this website and forum, it's proving invaluable. We recently bought a second hand D5100 and we are very impressed. We now have a long Sigma lens and a fixed 35mm lens, both of which work very well and (with the aid of your site) we are becoming more and more familiar each day.

However, for some reason, getting the kit lens to autofocus is beyond us, despite being able to focus it manually and despite occasionally being able to take shots, albeit out of focus.

I get the feeling that it'll be a combination of settings, but I'm not familiar enough with modern cameras (the last time we worked with cameras was 35 years ago) to be able to work it out, so any help/guidance would be very much appreciated.

I have a feeling that your cheat sheets will be something we will purchase once we become a little more familiar with how to work the camera - they look great!

Thanks in advance.

bruto

The kit AF lens has an A-M switch on it for auto focus and manual focus, and the camera itself also has a manual focus option in the menu.

It should work without any fuss if it is not broken, and if its contacts are working. To begin with, be aware that this lens should never be manually focused when it is set to A. Some lenses have a manual override, but this one does not. The focus ring locks, and if you try to override it, you will break it.

If this rig was purchased used, and the kit lens with it, be aware that it is possible the lens was broken when you got it. If so, it's almost certainly not economical to repair it. Check used listings, especially that of KEH.com, where you can find warranted used lenses in fine condition. It's almost always cheaper to replace this lens than to fix it. It is a decent lens considering the price, and a pretty handy one.

If it is not broken, try cleaning the electronic contacts with alcohol and reseating it.

If it's moving but not focusing accurately, make sure that your AF setting is set to a single point, and that the point is centered in the viewfinder. Multi Area AF will focus on something, but not necessarily what you want.

Also try auto focusing in live view. The live view uses a completely different AF system, reading focus off the image sensor instead of dedicated AF sensors. It's slower and less able to track moving objects, but it's dead accurate. If the lens focuses better on this than viewfinder view, the AF may need calibrating. If it focuses in live view but not at all in viewfinder view, the camera may need fixing.

JockTheCoalman

Thanks for the swift response. I guess I'm not having much luck and I do wonder whether it might be broken.

I cleaned the contacts, which were pretty dirty, but that doesn't seem to have made a difference. I changed the settings to single point and I have tried to focus in Live View, none of which, sadly, have made any difference.

So, I am back to thinking it might be broken. I appreciate your help in the meantime.

Jackie6

Did you check for your own optical calibration with the dial right next to the viewfinder?

Jackie6

Sorry, hit post too soon...You may find that this is off and you are actually unable to see the subject clearly (in focus).

bruto

It's a good reminder, since the diopter can be accidentally changed, and needs occasional tuning. But this lens seems not to be making clear photographs, and not to be auto focusing in Live View either. It's unclear whether the AF is moving anything at all.

I will add that if the focus ring moves when the lens is set to AF, then that's a pretty sure sign it's broken.

JockTheCoalman

Thanks to you both, again. I had checked the wee dial already but did so again just to be sure - no luck.

The focus ring does not move when set to AF, however.

Strangely (and I don't know if this means anything), if I switch to manual and manually achieve focus, then go back to autofocus, it seems to then be happy to shoot and, I think, might be trying to refocus if I point at some other distance. It seems to be that only one of the far right sensors in the viewfinder triggers.

I guess this probably means nothing though. Thanks again.

bruto

Have you recentered the viewfinder focus? Hit the [OK] button to make sure that only the center point is lit. If you're on single point focus, only one of those lights should light, and only the one lit will be the focus point.

If you have achieved reasonable manual focus, the focus priority will allow a shot even after you switch back to AF since it's the camera's focus sensor, not the mechanics of the lens, which tells it when focus has been achieved.

It's good that the focus ring is locked in AF, though. This rules out at least one major breakage.

I know you cleaned the contacts, but if they were dirty, don't forget to wiggle the lens a little too, just in case. I've never had to do that on mine, but my wife's D7100 needs the occasional wiggle to wake up the AF in the kit lens.

While trying to get things in order, don't forget that there's a menu option for a "rangefinder" which will allow you to do a pretty good job of manual focusing an AF lens. In place of the exposure compensation scale in the finder, when you're in MF mode or using certain MF lenses, the scale becomes a +/- focus scale. It's a little nicer than the go/no go dot.

JockTheCoalman

Well, it's the strangest thing!

I was about to give up and either speak to a shop for a quote or buy another (which made me think about whether I would willingly buy the kit lens - another story all round).

As a last gasp, I was reading your helpful comments again and it occurred me that perhaps I hadn't cleaned the contacts well enough, so I tried again, but nothing. Then I realized that there are contacts on the other side and as I was reaching for the cleaning fluid, I blew into the cavity (dunno why, I kinda think its a bad idea), and amazingly, it now works!

So, thanks to your forum, I now have a better understanding of how the lens is meant to operate and an understanding that I need to give it a more comprehensive clean.

Thank you.

bruto

Very glad that worked out. It's odd about those contacts. I've heard of some people having trouble, and others having none. Fortunately, so far, I'm in the "none" column. They seem to be both sensitive and inconsistent.