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11-24-2007, 07:31 AM   #1
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Sigma Tele 1.4 question

I troops.

I have the Sigma 300 F 4 and the Sigma 1.4 tele. For the first few years this combo has worked well, however the last few times i have used them, i notice the lens will not lock in focus with the tele on. I have tried it with a K10D and my PZ-1 so it seems not camera related.

Any ideas as to why this would happen, with the tele on. Bad contacts maybe.?? I have noticed a tiny bit of play with the tele on, but rotating the ring and focusing does not seem to do anything different.

Commnets appreciated.

Dave

11-24-2007, 11:57 AM   #2
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it is surprising that you can't autofocus, as I have no problem with an SMC 300 f/4 and the 1.7x TC. your combination is, or sould be fast enough.

have you looked to see that the autofocus drive is engaging? I find sometimes my 70-200 f2.8 does not engage cleanly with the focus drive on my PZ-1.

I have never had the problem on the DSLRs
11-24-2007, 04:34 PM   #3
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Its auto focusing, just not locking on focus. The 300 with out the tele AF's just fine.

I;m thinking its a contact issue, just not sure what if anything can be done at Sigma here in Toronto area.

Dave
11-24-2007, 07:28 PM   #4
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QuoteOriginally posted by pentkon52 Quote
Its auto focusing, just not locking on focus. The 300 with out the tele AF's just fine.

I;m thinking its a contact issue, just not sure what if anything can be done at Sigma here in Toronto area.

Dave
If it is a contact issue you shouyld be able to prove this by putting the TC on another lens (be careful, however, as the element in the TC is quite far forward and will not fit on all lenses, especially those with protruding rear elements.

If it really is a contact issue, it will be the one furthest away from the locking pin on the lens mount

11-24-2007, 11:49 PM   #5
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after hearing that you have some play, I'm guessing the 3 aperture ring screws loosened. I missed once in a lifetime shots in africa with my brand new lens as the loosening got so bad from the rough ride in the landrovers that the camera wouldn't even see the lens anymore and gave me a F-- ; I had to crank down and to the right to force the lens contacts to connect, sometimes. Once I got my hands on a mini screw driver set and tightened the screws, all was good again.
11-25-2007, 03:18 AM   #6
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QuoteOriginally posted by pentkon52 Quote
I troops.

I have the Sigma 300 F 4 and the Sigma 1.4 tele. For the first few years this combo has worked well, however the last few times i have used them, i notice the lens will not lock in focus with the tele on. I have tried it with a K10D and my PZ-1 so it seems not camera related.

Any ideas as to why this would happen, with the tele on. Bad contacts maybe.?? I have noticed a tiny bit of play with the tele on, but rotating the ring and focusing does not seem to do anything different.

Commnets appreciated.

Dave
The Sigma 300/4 is not compatible with the 1.4x converter for autofocus, Sigma's website states it is manual focus only.
Sigma - Lenses - Teleconverters
Second last lens. Strange considering it's f5.6 with a 1.4x and 2x converters are compatible with the f2.8s but that's what they're telling you and it's obviously right.
11-25-2007, 06:02 AM   #7
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Then explain to me, why it auto focused fine, for the past 17 months and is now on the frits. I checked with several sources before buying the tele

Dave
11-25-2007, 06:39 AM   #8
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QuoteOriginally posted by pentkon52 Quote
Then explain to me, why it auto focused fine, for the past 17 months and is now on the frits. I checked with several sources before buying the tele

Dave
I don't know about Sigma, but the issue, from what I have seen with pentax is that they will only gaurantee autofocus with lenses faster than F2.8 when using a TC.

For example the 1.7x AF TC that came out in the early 1990's and all manuals state this only works with F2.8 and faster lenses. This includes PZ-1, *istD and K10D (all of which I own.)

Having said that, none of my cameras can apparently read, because they all work perfectly with F/4.0 lenses. I use the 1.7x AF TC with my SMC 300mmf/4.0 , my Series 1 70-210mm f/3.5 and my SMC-M 100 f/4.

I have seen a few reports that the 1.7x even works with f/4.5 lenses, but I know for sure that F5.6 is just too slow. It is a question of available light for the autofocus. The camera really struggles with total combinations slower than f/6.7. This is why all autofocus lenses are at least this fast.

From a light point of view you should be OK at F/5.6

11-25-2007, 07:18 AM   #9
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Does the 300 f/4 have a switch for manual and auto focus on the lens? My Bigma does and if I inadvertently move the switch to manual, that thing will hunt all day long and never lock on....perhaps a switch? Or a bad switch? I've not see the 300 f/4 so I don't know what it has.
11-25-2007, 09:41 AM   #10
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Thanks for the replies so far. I tried the MF/AF switch and it will do nothing if in MF.

Just for a lark, i took the combo out side a few minutes ago, and it focused fine on everything i pointed at, then i gave the connection a bit of a twist, remember there looks like less than a mm play in the connection, then tried it again. It would not completley focus on what i was pointing at. I tried AF and MF and it was the same, the items focused on look like your shooting through a vasaline smear or something like that. It almost looks focused but its not.

I'm now thinking its a contact issue.

There is a Sigma distributor(Gentek) in the area, i;ll call them.

Dave
11-27-2007, 09:51 AM   #11
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Received a response from Sigma today, via email. I asked if the 1.4 tele was AF or only MF for the 300F4 and explained my problem.

I was told it sounded like it would need an adjustment, and to forward it to a Sigma repair place.

Dave
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