Can a busy background screw up IS.

I think you're just seeing camera shake. IS or not, the image looks like the camera shook.

I had problems getting sharp photos about a year ago. Out of frustration, I did some testing and was UTTERLY SHOCKED to find that I could induce hand-held blur (and lots of it) at shutter speeds of 1/250 with an 85mm lens when I was being somewhat careful. If I was rather careless, I got blur at 1/640 sec. When I got my shutter release technique under control. things got much better.

You're at the min shutter speed for a 400mm lens. I suspect that even IS isn't enough to compensate for poor technique (such as pulling to the side with the shutter finger).

Test on a tripod. Test with IS on and off. Test hand held and many shutter speeds. You'll eventually narrow it down to the cause.

Oh yea, and "tap" being used in the context of shutter release technique does not sound good. You should press the shutter 1/2 way, wait for it to focus and the IS mechanism to settle down (1 second?) and then continue the press to trip the shutter.

n1as wrote in post #6791368
..Oh yea, and "tap" being used in the context of shutter release technique does not sound good. You should press the shutter 1/2 way, wait for it to focus and the IS mechanism to settle down (1 second?) and then continue the press to trip the shutter.

Thats what i mean by tap. I guess tap is not really the right word to use.

In the uncropped image, do you see lens flare? (Could you post an uncropped version anyway? Just curious........)

Were the birds in water, also causing more light to be bounced in from beneath in addition to the side?

Both images look washed out to me -- I'm thinking if you had light bouncing around in the lens, in addition to anything else going on with AF, you'd see problems.

http://www.cambridgein​colour.com/tutorials/l​ens-flare.htm

gjl711 wrote in post #6791206
No, that is definitly something I want to try.

Gil I would try it with the IS off (on a tripod or monopod)...see if you have any better results. It could be many things (the older IS lenses don't have the panning IS option...I know you said you weren't panning but it may have seen even a slight movement to follow the birds as a stabilization moment). It just could be camera shake. (were you on a monopod or a tripod or handholding? On that lens IS needs to be turned off when you are using support). Worst case scenario, the IS is going out. How old is it?

S.Horton wrote in post #6791582
In the uncropped image, do you see lens flare? (Could you post an uncropped version anyway? Just curious........)

Were the birds in water, also causing more light to be bounced in from beneath in addition to the side?...

I can post the full image when I get home. There is no water, they were in a corn field and the other in a bean field.

Permagrin wrote in post #6791689
Gil I would try it with the IS off (on a tripod or monopod)...see if you have any better results. It could be many things (the older IS lenses don't have the panning IS option...I know you said you weren't panning but it may have seen even a slight movement to follow the birds as a stabilization moment). It just could be camera shake. (were you on a monopod or a tripod or handholding? On that lens IS needs to be turned off when you are using support). Worst case scenario, the IS is going out. How old is it?

The lens is just out of warranty . It has already been to Canon twice for focus issues. I am going to try some experiments with IS turned off though.

I have a very similar issue with my 100-400 but more and more I am convinced it is camera shake. I just don't think I can hold that long lens as steady as I used to and IS can't help anymore. I'm going to follow this thread but I think for me, some experimenting is next. That lens has been a champ for performance from day one and still gets the job done but more and more I seem to have less keepers.

PBeeee wrote in post #6791925
I have a very similar issue with my 100-400 but more and more I am convinced it is camera shake. I just don't think I can hold that long lens as steady as I used to and IS can't help anymore. I'm going to follow this thread but I think for me, some experimenting is next. That lens has been a champ for performance from day one and still gets the job done but more and more I seem to have less keepers.

That was my thinking as well, but this is only happening on pics with stuff in the background. Plus camera shake is more of a blur, but even. This has 4 very distinct shadows. Like it moved from spot to spot very quickly and paused.

I'm interested to see your full size pics. I was just out with mine and am not happy with the results. Hooded Mergansers on flat calm water, not a one is sharp on the duck but some parts of the water seem like they may be, so plain old user error, I have to look at these much more closely, but if I find a good example, I'll post it. I'm also dealing with the fact this lens is one of two that spent three weeks bouncing around (in a peli case) in a jet boat on BC rivers in September. The other lens has already been in for repair so I may actually have a problem, hence why I want to take more shots and nail it down.
Camera shake with so much background blur is less apt to seem even. I am back out this afternoon and am going to try more with it. And you do know that you should turn IS off on a tripod so that experiment is not going to tell you about IS? I'll put mine on a tripod to test AF, back & front focus issues but it won't tell me if IS is working correctly. I also want a day with much more light, this lens needs good light and I think is sharpest at f8 and the best light available.

If you're having a problem with the IS, it's not related to the background. It's possible that you'll see whatever your problem is more on a busy background than on a plain one, but the IS mechanism is located in the middle of the lens, and relies on a gyro mechanism to keep the image steady. It doesn't rely on a sensor trying to pick up an edge in the image and keep that in a fixed location. There are no optical sensors involved in the process.

I think it's a bad bokeh issue. I get this with my 70-200 sometimes, it depends on the nature of the background, distance from it and the subject etc. I just think the problem is amplified because you've focused on something closer in the first shot, so the background is even more OOF.

Here are the full images. No post processing applied other than resizing

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No, there's no way the background can effect IS. It can certainly effect focus, though.

The first image looks to me like one where the shutter was released before IS had a chance to fully kick in and do it's job. The fact that IS was still in process of moving the elements around causes apparent shake, instead of fixing it.

Notice in the first image that even things that are in focus show the effects of shake, such as the crane's eyes, which have double highlights

In addition, it could have just been more movement at that precise moment than IS could handle.

It depends upon the particular lens, whether or not you need to turn off IS on a tripod. I never do on my three IS lenses, but none of them is the 100-400 so I can't say for certain what's best with that lens.

You'd have better luck separating AF from the shutter release button entirely, with the *, via Custom function 4. Once used to it, I bet you'll wonder why you ever did it any other way and find your keeper rate will soar.

I think the reason it seems that busy backgrounds are effecting IS is that it's more obvious when there's a problem with the image, when the background is busy.

My conclusion for myself today is shake. Too little light, too low shutter speed, too unsteady. Myself, I need a sunnier day for that lens and days like today remind me of that fact. I think yours may also be shake. It looks awfully familiar...... I would not make any decisions about sending it for repair until you have shot it in great light, at least f8 and with a fast shutter/low ISO. That is my plan.

gjl711 wrote in post #6791203
Yes, thats what i meant by double tap. I shoot slow, hold over from film is guess, so I will press once for a few seconds, press again, maybe even a thord time until I'm happy with the focus. But it's worth experimenting a bit to see if my technique is causing the issue.

This sounds like the culprit to me. If you release the shutter to focus again, the IS will often spin down and then need to spin back up. This would effectively double the amount of time that is needed to let the IS settle. It may be more pronounced in places of higher contrast (busy backgrounds), since you are likely adjusting your focus more often to get it spot on.

I would recommend taking the focus off of the shutter button. By doing this you can hold the shutter button at half-press, which will keep the IS spun up. Then use the * or AF-On button to do your focusing. Then you won't risk disengaging the IS when you attempt to get better focus. Keeping the IS on with the shutter button will result in the IS being much more effective.

I'd like to thank all for their suggestions and help. I spent the last few hours debugging this lens and trying your various suggestions and have concluded that it is indeed the IS oscillating. Here is how I tested it.
I used a very simple target with very high contrast, an arbor in my backyard.
I used a very high shutter speed to minimize and camera shake, 1/3200
The pics are still hand held
I tried several different techniques.
What I found was if I focused with live view or allowed the camera to focus with IS off the pictures are spot on and sharp. Below are two pics. The first is focused with live view and the second is autofocus both with IS off.
http://farm4.static.fl​ickr.com …78260548_28f4bb​022d_o.jpg
http://farm4.static.fl​ickr.com …78260590_ce676d​96e3_o.jpg
However as soon as I turn IS on I start to get random sharpness. Sometimes it is good, but many times it's not. The key is that it takes about 5 to 10 seconds for the oscillations to subside. Anything less than 5 seconds and I get a soft image.
http://farm4.static.fl​ickr.com …78260622_d1aacd​ac0e_o.jpg
It also seems to get worse if the shutter speed drops which makes sense but it is also clearly seen at 1/3200.

So it looks as if this lens is headed back to Canon yet again. This is it's third trip back. I wonder if Canon is getting sick of me yet.