Sony 300mm f 2.8 lens and Sigma 1.4x teleconverter

[leon_pugh]

Today I purchased a Sony 300mm f2.8 lens (model SAL300f28G)

I used it with my Sony A100 camera.

It works fine. I like it.

 

Problem:

When I attached my Sigma APO 1.4x EX DG teleconverter, the autofocus would not work.

It works fine without the teleconverter.

Both camera and lens had the switch set to Auto.

 

I was able to focus manually and took some shots, but I was disappointed and intended to look into the issue.

Minutes ago I got online with Sony online support.

One of the analysts told me I had to put the camera in MANUAL focus mode for the teleconverter and the lens to

work.

I said that seemed strange. Did he mean the camera in manual and the lens in auto and everything would work?

He said it would and asked if there was anything else I needed.

Well that ended that.

 

I set up my camera and attached the 300mm lens. The autofocus worked fine.

I turned off the camera, removed the lens and attached the teleconverter.

Everything was set to auto mode. The auto focus did not work.

I set the camera to manual and left the lens on auto.

Guess what?

 

Yup, it doesn't work. (I didn't think it would).

I tried reversing the settings, lens manual, camera auto.

Nope.

I have not been able to get the SAL300f28G to autofocus using the (new) Sigma 1.4x teleconverter.

 

Anyone know if this is the case or is there a fix (firmware?)

 

Leon.

[leon_pugh]

BY the way.

With the teleconverter attached to the SAL300f28G lens, powerup time on my Sony A100 is about 15 to 30 seconds (estimate), the LCD on the camera stays dark. Same with powering down, the screen stays on long after you turn off the camera. So add that to the autofocus issue.

Using the teleconverter on my other lens (Sigma 70-200mm f2.8 APO) gives absolutley no problems.

 

Leon

[timb196]

I would guess that the issue is incompatibility of the Sigma TC with the Sony lens. A 1.4x would give yu an equivalent aperture of F4 whihc is well within the limits for the AF to work. I presume your Sony 300mm is the oldstyle (i.e not SSM) lens. I use my with both the 1.4x and the 2 x converters but both of those are matched Minolta units and have no problems. You might try calling Sigma and see if there is an issue as Sigma have had past incompatibility issues with Minolts/Sony equipment

 

Cheers

Tim

[leon_pugh]

I would agree with you Tim, that it is possible that the sigma 1.4x converter may not be compatible with the Sony 300mm 2.8 lens. This lens has a SSM "supersonic wave motor" focus mechanism. The autofocus "gear/attachement/screw" does not fit into anything that can turn. Instead a slot is cut out in the lens nount face and it looks like the focus screw fits in and sits still.

 

I really do not know how old this lens is. I was under the impression that it is NEW and has only been released very recently. Back in the end of June I was aware of the option to PRE-ORDER this lens and the release date was Aug 15 2008. I got mine on the 13th Aug 2008.

Some web searches seem to indicate Sony might have had another 300mm f2.8 lens out as early as 2006.

 

Still the problem remains and I am yet to get a clear answer from Sony.

 

Leon

[timb196]

I don't think you will get a clear answer from Sony. I doubt that the Sigma is compatible with aSony SSM lens. It

possibly has something to do with the notion that the camera body must know that it has an SSM lens attached and

some how that information is denied. Otherwise the body is going to to try and drive it with the in ln camera motor.T

The A100 should sense that automatically. The Sigma has SSM on one side and body drive on the other and may

not have the smarts to pass this along to the body. How old is the sigma?

 

Sigma has rechipped their lens in the pat because of incompatibility problems with Minolta lenses. I really think the

answer lies in talking to Sigma.

 

The 300 SSM is very new comparatively and was introduced along with the a100 what a couple of years ago. I have

a 300/2.8 G HS which is a non SSM lens and has been around since the mid 90s

[glyn r]

The sigma 1.4 teleconverter is dedicated to Sigma lenses. I have fallen foul of this myself. It either wont fit or doesn't work with other lenses.

[rdjc]

The converter needs to be attached to the lens b/4 it's attached to the camera....try that.

[leon_pugh]

Thanks Robert,

 

I have tried that ( attach converter to lens first). I remembered reading it somewhere so I looked it up. Apparently it DOES work with some lenses, though I do not understand why... shouldn't you turn off your camera BEFORE you change the lenses?

 

Anyway using this fix I get the same problem.