Sigma 50-500mm lens

[Ant]

Is anybody using one of these on a Nikon?

There's a tiny little switch on the bottom near the mount and I can't figure out what it's for. No mention of it in the manual. The only logical think I can think of is an AF/MF switch, but it definitely isn't one of those.

Has anybody got any idea?

 

[ferny]

I would have said the same. Two other things I can think of (which are probably wrong) are a macro switch which will allow the lens to focus closer to an object (that'll be at 500mm but it doesn't sound right) or that it is a digital lens with an anti-shock feature. Pressing the switch will enable and disable the anti-shock.

Is it an old or new lens? You may be able to get some info from Sigma's website.

 

[Ant]

It's a new lens....just got it yesterday

I can't find any info on the Sigma site either. The closest thing I can see to it in the manual is a 'Diaphragm control ring' which the Nikon fits have but the Canons don't.

What's a diaphragm control ring?

 

[ahelg]

I've heard that there is such a thing as a depth of field preview button on some lenses, it could be one of those. Except for that my guess is that it's an anti-shake function. I'm sure you'll find some sort of info on sigmas website.

I checked it out a little on the intrnet and it is supposed to have something called "full time manual focus". I'm not quite sure what this means but my guess might be that this button you are strugling with might activate this function.

Are you able to photograph the lens so we can take look at the button for ourselves.

 

[Ant]

Hi Ahleg.

Yes, I know about full time manual focus. It means you can still use manual focus when auto focus is being used. This switch has nothing to do with that. It also doesn't have an anti-shake feature.

Here's a pic of the offending article:

As you can see it seems to switch between the smaller set of numbers on top and the larger set below. The more I look at it the more I'm convinced it's diaphragm control....but I don't know what that is :?

 

[ahelg]

Well my camera also has large and small f-stop numbers so I don't think it has anything to do with it. To be perfectly honest it looks like the switch you use to detach the lens from the camera but I guess it's not that.

 

[Ant]

DOH, I've just played around with it and figured it out :roll:

It's an aperture ring lock

 

[ferny]

Ok, lets all form an orderly line so we can take it in turns to thwack Anton. :mrgreen:

 

[ajmall]

i could have told you that from the start! hehe all sigma nikon fit lenses have that!

 

[Ant]

Yes, I'm feeling a bit stupid.

Hey, I've only been using an SLR for a few months and I've only used G lenses so far :cry:

I've heard about manual aperture rings but never seen one for real before.