New lens - auto-focus doesn't work?
I've had a Canon 400D for about 6 months now and was reasonably happy with the 18-55mm lens it came with. I'm new to SLRs..

I wanted to experiment with other lenses, and bought the 85mm 1-1.8 lens recommended to me.

I can't get auto-focus on it to work. the AF/MF switch is correctly set on the lens, but it just doesn't whirr into action and focus on the subject..

Either it is broken or I am misunderstanding something basic about how lenses work?..

Comments (8)

Most likely there is something wrong with the lens. If the switch is set to AF, than the lens should focus. If it doesn't, than I'd take the lens back, or maybe test it on another body..

The only other logical explanation could be that the contacts on the lens are dirty, and it doesn't communicate with the camera. You could try cleaning them, but it doesn't strike me as a very likely cause..

Good luck,PeterThere's no problem so big that you can't run away from it!..

Comment #1

Hmmm... doesn't sound promising. I was hoping this was my problem. I don't have another body to test it on, but I put the 18-55mm back on and the auto-focus on that works fine.

Are there any settings that I might have got wrong? In the (very limited) instructions, it talks about 'full-time manual focusing' being possible even when AF is selected...

Comment #2

Unfortunately, that can hardly have anything to do with your problem. Full time MF only means that even in AF-mode you can adjust focus manually. With most consumer grade lenses that's not possible, you would wreck the AF-motor. However, with higher end USM-lenses you can focus manually in AF-mode without any risk to the focus motor..

It's not some setting you can adjust on the camera or the lens, it's just a built in feature this particular lens has..

There's no problem so big that you can't run away from it!..

Comment #3

Sounds like it might be faulty. If the AF works on the 18-55 I'd suggest you return it as faulty..


Pentax K100DFuji S5200Fuji E900PCLinuxOS..

Comment #4

OK, looks like a trip to the post office when they re-open.

Thanks everyone and have a good Christmas..

Comment #5

Cleaning the contacts on the lens? They can come dirty from the factory.It didn't seem like you did from your posts.A member of the rabble in good standing..

Comment #6

Thanks LM2. No, I didn't clean the contacts..

Do I need any special materials to do this, or will cotton buds do?..

Comment #7

No a clean pencil eraser and a soft cloth. Gently use eraser then wipe with soft cloth.A member of the rabble in good standing..

Comment #8

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