100-400 and 7D something odd

I have been thinking there was something wrong with this lens as most all my shots at a distance were way out of focus. I did a MA adjustment using the DotTune method last week thinking that was my problem. I finally got some sunshine yesterday and took my camera out to a marsh to shoot some waterfowl. I noticed something. I was shooting a duck setting on the water maybe 50 feet in front of me and then moved to some Canadians setting on shore further away and the camera would not lock. I moved to a closer subject and it would lock and then back again and it still wouldn't lock. I unhooked the lens and put it back on and then it locked. What could this mean. I was getting focus lock after that but any picture that was taken at a distance was out of focus when viewed at 100%. At what distance can you shoot and still expect reasonable results.

I'm not too sure what the issue could be, but when you try to focus farther away, does the focus scale on the lens move more towards infinity? Also try manual focus too.

You should get great results at any distance from close up to infinity, so I would do some controlled tests at home to make sure that there were no environmental factors at play like poor air quality or haze at play in this case. Also reset the MFA to zero.

Are you using a filter? Did the focus just hunt?

When I was trying to focus on the subject farther away it did not hunt. It wasn't doing anything until I unhooked it. I did not notice what the focus scale on the lens was doing. I was mad at myself as I forgot my tripod so I could use it to make sure it is not me but by the time I got home it was late and the sun was gone. It is cloudy out today with some light rain so I can't do it today either. The kind of pictures I took yesterday are stuff I usually like to shoot with great results. I did not have a single picture sharp or even close to being sharp at a distance.

I have used my 100-400L at all distances from minimum focusing distance of around 1.8 metres to around 385,000 kilometres (shooting the moon) with no trouble locking focus (in one shot mode) or tracking the subject (in AI servo). I certainly didn't see any problems focusing at the sort of distances you are talking about. Looking at the example images on your other thread, it does seem that you may have something wrong with your lens. It is hard to rule out user error (which is the usual culprit) completely, but I do lean towards equipment problems in this case.

Do you know anybody else near you, who has the same lens? This is where local camera clubs are handy, as it is easy to get together with somebody else and swap lenses for a test. You shoot with theirs and see if you get good results shooting as you have been, they shoot with yours and see if their shots go to crap (no offence meant).

Possibly try to clean the contacts on the lens and camera to see if that helps? Check online how to do it. Sounds like a communication error with the two.

I assume you are using center point focus and are you on one shot or AI servo?

mike325 wrote in post #16814291
Possibly try to clean the contacts on the lens and camera to see if that helps? Check online how to do it, but I believe people use a clean pencil eraser to do it. Sounds like a communication error with the two.

Yes, some people do do that, but they shouldn't. Canon specifically say that you should NOT use a pencil eraser to clean contacts as the gold surface is very thin and doing that can remove it. Which CAN lead to contact issues even if you didn't have them before.

From the Canon website, a direct copy and paste. Text in bold is their emphasis, not mine:

^ Cool, just edited mine to remove that bad idea, thanks for clarifying.

For the OP, if your other lenses seem to be working fine, I would suspect that your 100-400 is acting up a little and might need to be sent to canon to be fixed.

I am going to take it out and photograph with a tripod a tree at different distances the next day we get some sunshine as someone suggested. If I were to send this in, can I send it to one of the Canon Authorized Service Facilities in the US? The closes one to me is in ITASCA, IL

sandpiper wrote in post #16814287
I have used my 100-400L at all distances from minimum focusing distance of around 1.8 metres to around 385,000 kilometres (shooting the moon) with no trouble locking focus (in one shot mode) or tracking the subject (in AI servo). I certainly didn't see any problems focusing at the sort of distances you are talking about. Looking at the example images on your other thread, it does seem that you may have something wrong with your lens. It is hard to rule out user error (which is the usual culprit) completely, but I do lean towards equipment problems in this case.

Do you know anybody else near you, who has the same lens? This is where local camera clubs are handy, as it is easy to get together with somebody else and swap lenses for a test. You shoot with theirs and see if you get good results shooting as you have been, they shoot with yours and see if their shots go to crap (no offence meant).

I don't know anyone that has this lens as I don't belong to any camera clubs. Maybe I can find someone here in central part of Iowa though. That is a good idea.

When using isopropyl alcohol to clean the contacts, the cloth being used should be just MOISTENED, not drenched, with the alcohol before using the cloth to wipe the contacts off.

This wouldn't explain all of your problems maybe, but, did you move your Focus Limiter Switch to the correct position?
I'm not saying you're a dummy, but sometimes it might be the simplest things.
I know I have had that problem I spoke of.

The 100-400mm L is a good lens, I had one for around 5 years, I don't remember having that exact problem, but I did have focus issues that was 'me', rather than 'it', and it was the switch I forgot to put in the right position.
Now I have a different L lens, a couple of weeks ago I was trying to shoot a bird that was about 20' or so away, I tried and tried, but nope... It turns out that somehow I accidentally had turned off the Auto-Focus Switch, I guess it rubbed up against my leg and turned it off somehow.

Randy

recrisp wrote in post #16815666
This wouldn't explain all of your problems maybe, but, did you move your Focus Limiter Switch to the correct position?
I'm not saying you're a dummy, but sometimes it might be the simplest things.
I know I have had that problem I spoke of.

The 100-400mm L is a good lens, I had one for around 5 years, I don't remember having that exact problem, but I did have focus issues that was 'me', rather than 'it', and it was the switch I forgot to put in the right position.
Now I have a different L lens, a couple of weeks ago I was trying to shoot a bird that was about 20' or so away, I tried and tried, but nope... It turns out that somehow I accidentally had turned off the Auto-Focus Switch, I guess it rubbed up against my leg and turned it off somehow.

Randy

I made sure as soon as I noticed it wasn't wasn't focusing right to check that switch. I have done that before. I was shooting something close and forgot to put it back. I hope it is a user error but I am starting to think something is wrong. I won't have a sunny day until Wednesday it looks like. I will be using a tripod so do I really need the sun to test it out?

One thing I would do is to ask (here) for someone to take a shot of their 100-400mm L and let you see the other settings, there's one (that I can't remember what it's called) that may also be a problem, I'd check all of the easy stuff first before doing too much.

You should also take a shot of yours and possibly someone can see something that 'may' be it, you never know.

If you have the time, try it on a tripod, even if it is a cloudy day, not dark and cloudy, but it should tell you what's what.
On a tripod it should be clear to you what it is, focus-wise anyway, you'll know if it's a weird thing or not, I think.

Good luck, and I hate to hear that you're not having fun with it, but hopefully it's something easy.

Randy

recrisp wrote in post #16815832
[COLOR=Navy]One thing I would do is to ask (here) for someone to take a shot of their 100-400mm L and let you see the other settings, there's one (that I can't remember what it's called) that may also be a problem

If you'd care to explain I'm happy to shoot an example, but I have no idea what it is you are after.

recrisp wrote in post #16815666
This wouldn't explain all of your problems maybe, but, did you move your Focus Limiter Switch to the correct position?

The limeter switch set incorrectly would have shown the issue in reverse. Focusing close might not lock but at distance it would be no issue.

To the OP, one thing you might check is to see if there is dust on your mirror. Though dust on the mirror won't affect the final image, if it is an the wrong spot, it may affect your AFs ability to lock focus.