Help! AF problem with Bigma - DPChallenge Forums

Canon EF 24-105mm f/4.0L IS

03/08/2006 07:07:17 PM · #1

I don't know if it's the lens, the operator, or the technique. ;/

I just picked up a brand new Sigma 50-500 as an early bday present. Everything i've read about these lenses indicate they autofocus fast and accurately. Mine seems to creeeeeeep to lock in focus. I've tried bright light, low light, both ends of the zoom as well as in between. Occasionally it will lock right on, but if the focus is way off, it takes forever. I can hear the motor if i put my ear on the lens, and it sounds like it has no power. I replaced the battery with a fully charged one, and reset the menus to the default to make sure i haven't changed a setting that would cause problems. Is there something i've overlooked, or could i have a defective lens?

All suggestions appreciated.

val

zeuszen

Canon EOS-1Ds Mark II

03/08/2006 07:09:40 PM · #2

How's the light? Do you focus on an area with good contrast?

Canon EF 24-105mm f/4.0L IS

03/08/2006 07:22:32 PM · #3

Originally posted by zeuszen:

How's the light? Do you focus on an area with good contrast?

Yes, i've tried a shot on a high contrast target with light provided by shop lights bounced off the ceiling. There doesn't seem to be an appreciable decrease in the time it takes to focus.

zeuszen

Canon EOS-1Ds Mark II

03/08/2006 07:30:05 PM · #4

This is an f/4-6.3 lens. It would take a well lit subject with good contrast not to hunt...

Canon EF 24-105mm f/4.0L IS

03/08/2006 07:52:07 PM · #5

Originally posted by zeuszen:

This is an f/4-6.3 lens. It would take a well lit subject with good contrast not to hunt...

Yes, i'm aware. Which is why i used the very bright shop lights, on a very contrasty subject as one of my test shots. My 70-300 is a f4-5.6, and it focuses more than twice as fast at 300mm than the Bigma does at 50mm. Same target, same lighting.

The way it's acting, is not like it's hunting. It's like the motor is straining to get to the focus point. Like i said, if i put my ear to the lens, i can hear it very faintly, and it really sounds as if it has no power.

I guess it's going back to the store. :(

Message edited by author 2006-03-08 19:53:37.

zeuszen

Canon EOS-1Ds Mark II

03/08/2006 07:56:21 PM · #6

I'm sorry to hear. I'd have it looked at. Faulty motor?

03/08/2006 07:58:34 PM · #7

Originally posted by zeuszen:

I'm sorry to hear. I'd have it looked at. Faulty motor?

Ya, that would be my guess. Since i've had it less than 2 days, i'm not going to hassle with repair, just going to get it replaced. Hopefully i have better luck with the replacement. Thanks for the help.

jbsmithana

Nikon AF-S DX Zoom-Nikkor 12-24mm f/4.0G IF-ED

03/08/2006 08:02:51 PM · #8

I'm not sure but I believe there is an old and a new model of that lens. You might want to check if that is the case.

Sigma 20mm f/1.8 EX Aspherical DG DF RF for Canon

03/08/2006 08:06:39 PM · #9

Originally posted by jbsmithana:

I'm not sure but I believe there is an old and a new model of that lens. You might want to check if that is the case.

This is the DG, which i believe is the newer model.

yido

Canon EOS-5D

03/09/2006 09:21:31 PM · #10

can you focus it in MF?
the minimum focus of this thing is rather long, so if you try to focus in small rooms, it won't focus but just hunt.