Sigma 120-300 F2.8 OS

[005269]

I'm currently having a few issues with this lens. Using it on my Nikon D7000 at the weekend it worked fine for an hour or so before suddenly failing to autofocus? It wouldn't adjust focus at all except manually and seemed to become noisier whilst trying to operate. The camera battery indicator had dropped by one indicator. Trying the lens on my D700 and again on the D7000 now the battery has recharged, its back to working fine? I just wondered if anyone else had noticed af issues with a battery not quite 100% but nowhere near fully discharged? The issue was the same both with and without a teleconverter.

 

[specialman]

Was it any different when you switched OS off and on? Could be some form of power drain due to the OS Are the len contacts clean?...

 

[tdodd]

I bought the Canon version of the lens fairly recently, new from Jessops, and I've also been seeing some problems with the AF. Sometimes it works fine. Other times it refuses to focus or focuses so slowly that you need to watch and wait for maybe 10-20 seconds to see the AF creeping slowly towards its goal. It's also the case with and without a TC. No idea what causes it and which element is the problem - camera or lens - but sometimes detaching and reattaching the lens works. Battery does seem to plummet quicker than normal with this lens too. If using a TC I've read guidance (from Sigma and elsewhere) that the TC should be attached to the lens before attaching both to the camera. While that might be good advice for various reasons it is not a cure for this slow focusing symptom. I haven't spoken to Sigma yet, but I think it might be time to.

 

[005269]

It just suddenly stopped focusing. I had the OS on at the time but tried turning it off. I also turned the camera off, re mounted the lens and removed the tc etc, all to no avail. To the best of my knowledge all the contacts are clean although I couldn't be sure which way around I mounted the tc etc. I did have problems with the lens in May. Sigma replaced the AF motor as it packed up, exhibiting similar symptoms as above. I presumed it had gone again but that's not the case, it's working fine again now. The lens acquires focus marginally quicker on the D700 than the D7000 but I'm generally happy enough using either body. It really does have a few strange little quirks that take some getting to know. DOF is paper thin wide open and that's caught me out a time or two, overall though I'm more than pleased with the image quality especially using the tc's, its just every now and again it throws a 7 and misbehaves! On this occasion, I was photographing kestrels handheld with the lens elevated, os on and using back button af and all I can think is that I've drained the battery to a point where its not got enough left to function properly? The camera lcd battery indicator though dosen't reflect this? I have a Sigma 150-500 which is a lot easier to get on with but not in the same league IQ wise at the longer end of its range. I've lent my lens to a friend for him to put it through its paces this weekend on his D3 and D4 and see if he can replicate the issue in question. If he can't and he's happy enough then I think it's a battery grip and extra spare batteries before I go to Gambia in November as it will be used on the D7000 a lot over there.

 

[tdodd]

I took mine to an airshow today and fired off around 1250 shots with my Kenko 1.4X and 5D3. AF worked perfectly (as far as I could tell from chimping) and the battery was down to 45% from full after the 1250(ish) shots. I didn't use IS much as it was proving very tricky for anything moving, including with panning mode, and I was better off taking my chances without IS, even at 1/160 and 420mm.

I have a suspicion that the AF problem may be down to poor contact between lens and body, but I can't be certain of anything yet.