Posted by Dottie Short on February 23, 2011 at 2:35 PM
I've had my 500mm lens for about six weeks now and I've experienced a quirky thing when trying to focus the lens when I first turn the camera on. The lens won't focus unless I help it by partially focusing the lens with my hand. After that initial partial focus with my hand, it continues to focus by itself quickly and quietly. It seems that the lens has trouble focusing only if the focus is off by a great margin. If the focus is reasonably close it will usually focus the first time.
Let me set the scene...I'm on a tripod and have the lens focus switch set to 10m - infinity...stabilizer off...focus preset off...the bird is 100 - 300 feet away.
I talked to Canon today and the person I spoke with seemed to be at a loss to suggest anything. I don't want to send it to CA and pay the huge shipping and insurance fee and be without my lens.
Has anyone experienced this, and can anyone offer any suggestions as to what I might do to get the lens to focus immediately this first time without my help. I missed some great whooping crane flight shots monday because I had just attached the camera to the tripod when they took off. Of course my lens would not focus.
Posted by Luke Ormand on February 23, 2011 at 2:54 PM
I have this issue with my 300 f4 + 1.7X TC if the focus is starting by being way off (say it's focused to 3m but my subject is 50m away).
I've never used a 500mm buy my guess this is normal if your subject is very far away and small in the frame because your lens doesn't know what to focus on because the subject is tiny. You can test this theory by trying to focus on a bird in flight that's far away and then finding a building or something big at a similar distance and trying to focus. My guess is the lens will focus just fine on the large subject.
If what you're trying to focus on is so out of focus that the autofocus sensor can't figure out what to do, it's going to have some problems. There's just no way around that. I manually assist or prefocus quite often - otherwise it's even hard to find the target in the viewfinder! If you set the focus distance switch appropriately it can help out a lot.
Posted by Mark Seaver on February 23, 2011 at 11:13 PM
Have you tried adjusting what segment(s) the auto focus is using. You may find that using a single segment and pointing that right at your bird improves the performance. I find your problem interesting because I'm starting to think about buying that 500mm lens.
Posted by Garry Revesz on February 24, 2011 at 12:28 AM
I have a 500 as well Dottie, and once in a while I've noticed a delay in focusing, and then I say to self; Dahhh! you're pointing at the sky and there's nothing there, but as soon as I point it at any object or bird, the lens immediately snaps into action. The one thing you might want to take note of Dottie, is the AF selection; single point may take a split second longer than auto select, etc. So don't dispare. It is one amazing lens but it does take time to hone the skills required to tame it.
Garry
Posted by Paul DeCesare on February 24, 2011 at 1:42 AM
Dottie, I've owned the Canon 100mm Macro and two 100mm Macro IS lenses, and that has happened on every single one of them if I focus on a close object (say, 5 inches away) then try to focus on something 20 feet away. Your lens is fine, the problem is that auto-focus need contrast to have something to grab onto. If it's blurred out totally or pointing at a sky, the AF sits there dumbfounded. Do test it out, but I just think it's one of the quirks of AF.
Discussion
5 repliesLet me set the scene...I'm on a tripod and have the lens focus switch set to 10m - infinity...stabilizer off...focus preset off...the bird is 100 - 300 feet away.
I talked to Canon today and the person I spoke with seemed to be at a loss to suggest anything. I don't want to send it to CA and pay the huge shipping and insurance fee and be without my lens.
Has anyone experienced this, and can anyone offer any suggestions as to what I might do to get the lens to focus immediately this first time without my help. I missed some great whooping crane flight shots monday because I had just attached the camera to the tripod when they took off. Of course my lens would not focus.
I've never used a 500mm buy my guess this is normal if your subject is very far away and small in the frame because your lens doesn't know what to focus on because the subject is tiny. You can test this theory by trying to focus on a bird in flight that's far away and then finding a building or something big at a similar distance and trying to focus. My guess is the lens will focus just fine on the large subject.
Garry