Problem with Canon 1.4X Extender - Any advice?

I've been successfully using the Canon 1.4X II extender with my Canon 500mm f/4 IS lens and Canon 7D body for the last six months or so. I purchased the extender new. Up until recently, I've had no serious problems with the lens/extender combination other than the inevitable slowing of the AF and a bit of focus hunting in low light. The image quality has been very good to excellent. Suddenly (over the last week, comprising about three shooting sessions), the images are almost all coming out soft. The problem is particularly bad when in AI Servo mode, but it also occurs in One-Shot. I removed the extender and the images from the bare lens are excellent, which leads me to suspect that the extender is no longer functioning properly. Other than trying to clean the contacts on the extender (which don't look at all dirty), is there any other troubleshooting I should do? And if the extender is indeed malfunctioning, what exactly can Canon do? It seems like a pretty simple device: no moving parts, no fancy electronics.

Thanks,

John

Could you post a shot with the 1.4x on a tripod? And also post a 100% crop. Please include EXIF data. It's possible that you may need to microadjust your 500/1.4x combo or clean your contacts. I'll reserve judgement until I see a sample frame.

Strange John. When I get a sudden change in IQ like this I invariably end up putting it down to unstable air which causes shimmer and your AI Servo with hunt like made trying to find focus. If you have an image with a catchlight, it will have a tell-tale look if you have shimmer.

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Could you post a shot with the 1.4x on a tripod?

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Doug, thanks for the response. There's no need for me to post an image: I've taken literally thousands of exposures with this combination of lens and extender in the last six months -- both hand-held and tripod-mounted -- and the images have been consistently very good to excellent in sharpness until recently. As an example, previously if I shot 10 exposures of a duck swimming slowly past me -- not a challenging situation for the AF system, by any means -- at least 8 would be critically sharp (most of the time all of them were sharp). In the last three outings, with that same scenario, 8/10 have been hopelessly soft!

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It's possible that you may need to microadjust your 500/1.4x combo

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With regard to microadjusting the AF, I did do that when I first acquired the 500mm f/4. The bare lens didn't need any adjusting, but the lens with the extender required an adjustment of -6, and that's what I have been using since. Is it possible that over time -- or suddenly -- the required amount of microadjustment can change?

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When I get a sudden change in IQ like this I invariably end up putting it down to unstable air which causes shimmer and your AI Servo with hunt like made trying to find focus.

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John, can you expand on what you mean by "unstable air"? It has been fairly windy here in Southern California lately, but the humidty has been relatively low, and I don't think there is anything unusual in the atmosphere that might interfere with the image. But AI Servo is definitely "hunting like mad" when I use the extender. In fact, in a few instances the lens with the extender attached actually seemed to stutter when trying to achieve focus. I didn't notice anything like this when using the bare lens.

Thanks for these suggestions, guys. I'm going to go out again early tomorrow morning to try and shoot the baby Avocets at the SJWS and I will see whether the problem repeats itself.

John

Hi John, have you checked that all the location screws tight on the extender, so there is no play in the housing of the extender?

Does it also happen with IS on and off? Do you have another lens you can try it on? Another body? I know you said you removed the extender and it works correctly...the body or 500 could be having trouble reading the extender or functioning with the extra loss of light.

John,

A quick test to see if it is a microadjustment issue: place the camera+tc+lens on a tripod and aim at a static flat subject, say 50 feet away, that has lots of fine detail. A brick wall or newspaper taped to a wall works well, but even a bird sitting on a stick works.

Next, use a cable release and half press the shutter to engage focus. Take you finger off the focus and start live view. Zoom in to the maximum with live view on an area with fine detail. Now half press the shutter to engage focus. Does the image get sharper? If so, you need microadjustment. If not, is the image sharp?

Regarding posting a sample, and your response to John C.'s question, I agree atmospheric turbulence can certainly be a factor especially if one images subjects further away. So posting 100% crops of before you had the problem and after is a good idea.

Roger

Thanks, everyone, for these additional suggestions. I will try all of them in the next several days to see if I can sort out the issue. I went out early this morning hoping to evaluate the situation further, but the sky clouded up the minute I arrived at the SJWS (typical California spring weather...).

John

Cloud is good John!

Is there any way to borrow another 1.4x TC ans try the combo to rule out a faulty tele-converter?

I also had the exact same problem with the Canon 1.4 II extender. I tried several camera bodies and camera lens combinations, on tripod, off tripod, many different days and even different countries. I sent the 1.4 back to Canon for cleaning. It just never again worked properly and I finally gave up on it and purchased the new 1.4 extender. The new one works just fine (thank goodness). I still do not understand what happened with my original extender but I could no longer tolerate the lack of reliability and was running out of hair to pull out :S3:. Good luck to you.

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Cloud is good

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John, there are clouds and then there are clouds. When the Pacific Ocean marine layer moves in, I pack up my gear and go home!

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Is there any way to borrow another 1.4x TC

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Michael, I was thinking of renting an extender. I may try LensRentals, as the local camera stores don't seem to maintain their rental equipment in very good shape.

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I also had the exact same problem with the Canon 1.4 II extender.

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Nancy, the experience you describe is my greatest concern: that the extender has failed in some unfixable way and that I will be chasing my tail trying to figure out what has gone wrong. Did you purchase your Canon 1.4X II new? If so, how long did it work before it began malfunctioning?

John