5 replies to this topic

[Tiago Brandão]

Hi!

 

I've had an Nikon d3500 with the 18-55 and 70-300 VR kit lenses for about a year, and until recently the autofocus has works as I expected (I almost always use single point AF and AF-C with back button focus). But now it has a weird problem where the central af point works weirdly. It hunts endlessly and it always misfocuses. Sometimes it just goes to minimum focus distance and stops trying to focus. It is only really able to focus reliably on really bright objects, like lights. I'm pretty sure the problem is in the autofocus sensor itself, as all the other points still work normally.

 

Also, when looking through the viewfinder, there's a small weird circle around the middle af point where the image looks a little but brighter than the rest (It's kind of hard to describe it, I can try to photograph it). It has always been there, so I don't think it's related, but I though I'd mention it.

 

My guess is that there's some dirt in front of the af sensor, but I've tried to «shake it off» (since I don't have a blower) but it's still the same. Any ideas on what it could be?

 

I hope I was clear explaining the problem. If not, please say it so I can try to explain it better.

 

Thanks in advance!

[Bengan]

Take away the lens and take a photo showing the mirror and, if possible, one of what is seen through the viewfinder. Post those here. It sounds like a problem with your mirror

If you're seeing something in the viewfinder then it's not on the sensor. Sensor dust are seen as spots on photos and in live view.

[Tiago Brandão]

Take away the lens and take a photo showing the mirror and, if possible, one of what is seen through the viewfinder. Post those here. It sounds like a problem with your mirror

If you're seeing something in the viewfinder then it's not on the sensor. Sensor dust are seen as spots on photos and in live view.

 Thanks for the reply!

 

Yeah, when I said dust on the sensor, I meant on the af sensor, not on the image sensor.

 

So anyways, here are the photos you asked for (I hoped they are as you asked) as well as a video where you can see the problem, where I cycle through a few af point, but only the middle one can't focus)

 

The photos and video are in this link. I think it's easier than uploading it direcly here. Hope you don't mind

Microsoft OneDrive

[Bengan]

It looks like the mirror has scratched. Have you tried to clean it in some way? If not, do you know what caused them?

Apart from those scratches, I can't really se what might be the problem. Perhaps someone else can help.

[Tiago Brandão]

It looks like the mirror has scratched. Have you tried to clean it in some way? If not, do you know what caused them?

Apart from those scratches, I can't really se what might be the problem. Perhaps someone else can help.

Yes I noticed them too for the first time today. I don't recall ever touching the mirror with anything, I'd be too afraid of screwing up something, and those scratches look too straight to be made by random debris inside the camera, so I'm a bit at a loss.

 

Anyways, thank you very much for your time!

[Bengan]

My guess is that this is something that will have to be fixed professionally. You will have to decide if the cost is worth it or if you should try to buy a used body instead.

You can still use LV with center focus