Sigma 150-600 C Focus issue

I decided to give the Sigma 150-600 Contemporary a try, no complaints with the Tamron but thought the added features of the Sigma would be nice to have. Well I played around with it in the back yard the last 2 evenings and am really disappointed with the AF. Basically it's doing the same thing the Tamron's did before the Firmware update. Camera body is a 7DII. Bare lens, No TC....... In Ai Servo I focused on a tree 10m away, then shifted to a tree aprox 70m away and the AF just froze. Focused on the far tree, moved to the close one and it just froze. This was at 600mm, if I backed it off to 400mm the focus shifted almost perfectly. At 500mm it was hit and miss, then to 600 again and no shift at all, didn't even try. Focus limiter was set to "FULL" but I also tried 10m - Infinity with the same results.

I'm really surprised that I've never read anything about this on here. Anyone else notice this or just a defective lens ?

Do you have the option is AF not possible turned off so it won't try if it's to far out of focus. I don't know what cf# that is in your body

I have "Lens drive when AF impossible" set to ON

Your the first of this issue I have heard. Someone had issue kinda like yours and that setting was set to off and the camera didn't try. My copy has none of that issue. It zips from near to infinity with no hesitation.


Just to be sure. Just grabbed mine set to min focus at 600 used aiservo for a target about 100feet away and grabbed focus in well under 1 sec. Then focuses on an object about 15feet and same fast speed

Just to be clear, this is in AiServo with the shutter/AF button depressed the whole time while switching between objects. If I bump the AF it will acquire AF fast near or far, just wont switch between on it's own.

Thanks.

Just tried that. Mine does the same. I think it's normal. I will try with my 70-200 as well.


Just tried the 70-200. There is a little delay not as much. But I don't see that being an issue ever. I can't think of anytime I was ever shooting I needed to track an object at infinity then instantly at close distance. A quick release of focus button and press again gets it locked no matter the distance then start tracking.

not certain but it could well be the AF case you are in and its setting for sensitivity/delay for changing target.

tried that..set my camera to switch tracking to fast so it will change focus on subjects as fast as the camera will allow. it still kinda hung. I thin its normal and kind of an unrealistic issue that would probably ever come up in real world shooting. I just cant see why you need to hold down the focus button to track going from 100+feet to like 15feet in an instant. letting go of the focus button for a fraction of a second and pressing again makes everything good to go.

05Xrunner wrote in post #17593546
Just tried that. Mine does the same. I think it's normal. I will try with my 70-200 as well.


Just tried the 70-200. There is a little delay not as much. But I don't see that being an issue ever. I can't think of anytime I was ever shooting I needed to track an object at infinity then instantly at close distance. A quick release of focus button and press again gets it locked no matter the distance then start tracking.

It's not that there is a delay, it won't shift at all, doesn't try. If the objects are closer together it will shift.

What happens a lot with BIF, at least with me is that the bird is missed and focus goes to the background. It's much easier to be able to just move the focus point onto the bird to get the lock with the AF still active, sometimes the focus has to be bumped and it's easy to miss the second time as well. I'm not talkin slow movers here my BIF shots are mostly ducks.

The other thing is that it shifts fine at 400mm but gets worse at the longer focal lengths.

Negative. I used case 1 all defaults. It's not that there is a delay, it doesn't shift focus at all.

well have to say your the first person to ever bring up an issue like this. I am curious about some of the other Super tele out there that are over 400mm if they act the same way

When the Tamron did this it was a problem for most but some still said it was no big deal for them, guess it depends on shooting style but the bottom line is that it isn't right. Tamron eventually came out with a firmware fix and it corrected this same issue. If I'm the only one with the issue, I'll try another lens, but if this is normal I'm goin back to the Tamron. All my Canon lenses have handled this situation just fine as well.

I suspect that if you think about it logically, Servo mode is to track a moving object, once it has acquired that object it will continue to track it, moving the camera to a totally different object that is nowhere near where the lens had it's last registered position is no doubt got the lens saying hey where did it go!!

AIServo is for tracking objects not selecting a new target.

Not strictly true.

AI Servo is meant to continuously focus on whatever is under the selected focus point, or rather, to ensure that whatever is under the selected focus is point is always in focus, with the only limitation being the focusing speed of the lens motor. Tracking moving objects is a feature which is made possible using AI Servo.

If the lens said "hey where did it go?"... it should at least say "screw that ... let me find another target", like all lenses I own do.

05Xrunner wrote in post #17593487
Just to be sure. Just grabbed mine set to min focus at 600 used aiservo for a target about 100feet away and grabbed focus in well under 1 sec. Then focuses on an object about 15feet and same fast speed

100 feet is a long way from infinity. I sent my Tamron in for the firmware fix, but before that it had no problems in the type of situation you describe, but it had problems going from infinity to close-up.

It is sort of funny, after all the flack the Tamron received for this problem, that some figure that it must be "normal" for the Sigma. Put any lens on your camera in AI Servo, press your focus button, and move the camera from a target at infinity to one at your feet. The focus should follow what you are pointed at until you reach the minimum focus distance. Period.