I think i know what you mean about spastic focusing
in low light if it hunts due to not enough contrast it can sound jittery because it hunts over a very short distance rather than racking the entire focus range like a canon lens hunting
while it can sound a bit wierd it will lock focus sh!tloads faster
This might be, but I am also starting to wonder whether the body (my 5D II) comes into play here? Here is what I wrote in a different thread here today:
Might I ask a question which might seem quite uninformed?
My own camera is a 5D II with grip, and I am also now borrowing the 1Ds III. I have previously borrowed the 85 F1.2L, but then shot it with my 5D II. I had to throw away most of the pictures I shot with that combo (ca. 80%), and that is the reason I went with the 85 F1.4 Sigma instead (that and price of course:). I have now also borrowed the 85L, and I am using it on the 1Ds III, and I have an exponential growth in keepers.. This might be because I am getting better at taking shots, but I cannot shake the thought that the combo of the AF on the 1Ds III and the 85L works better than the 5D II and the same lens?
Were you using the center point of the 5DII and was the lens MFA'd first? Shooting wide open with outer points on the 5DII will give lower keeper rates than the center point. My old crop camera didn't have MFA and worked decently well with fast lenses. My 5DII needs an adjustment of about +10 on the same lenses. Were you using AI servo or single shot?
I rarely shoot with I servo (a few times when shooting high speed bikes on a track, and some testing with birds, otherwise I shoot AI Focus as a default (most of my shots are of people and things that hardly move). I have never microadjusted any lens on my camera, and have not seen the need...? That lens is the only one that I have struggled with, but as mentioned above, it works quite well with my borrowed 1Ds III. It could be as you suggest that microadjustment would solve it, and if I were to buy one I would have to do it. However I do not see myself buying one in the near future, since I just got my Siggy 85 1.4 which I am very happy with, and I have set my eyes on the new 24-70, and I would like to replace my 50 1.4 (just got it back from the shop) with the 1.2. Too many cool lenses, and not enough money:)
As a sidenot, although I love my Siggy 85 1.4, I have to say that the bokeh on the 85 1.2 seems more dreamy, or buttery, and color rendition is brilliant.