70-200 f/2.8L blurry at 200mm + low aperture

[izzi]

I have been using this lens with my 6D for years (admittedly not regularly - only when I travel), but have recently noticed that things get blurry (moreso toward the outer edges of the image) at 200mm with lower apertures. I can already see the blur through the viewfinder. At higher apertures, photos actually come out less blurry than what I see through the viewfinder. Here are some test images (200m, one-shot AF on the text - I've also tried MF with same results).

f/2.8:

f/8.0 - not as bad:

I'm assuming there's some sort of lens damage - perhaps moisture? Any tips to try out in the field? I won't have access to camera repair for a few months. Thanks in advance!

[izzi]

@FMTrindade I appreciate your validating that there was clearly something wrong with the lens beyond user error, without getting too technical about the test 😂 I also appreciate everyone else's time and suggestions. Should have emphasized that my main question was not whether there was something wrong at all, but whether anyone had tips for (temporary) fixes in the field.

In case it's helpful to anyone with a similar issue - a heated dry box helped reduce the blur a little, but not for long. I eventually brought the lens in for repair. It did indeed have a busted element, probably from an unlucky knock, which required the whole group to be replaced.

[FMTrindade]

Hi.

If a Heated dry box helped a bit, most likely you had humidity and/or fungus.

Glad you could make it work.

There is always a way to make a quick test:

The front element is usually the focus fine tuner. And if it is tilted or disaligned, then the image will never get ok.

So, first thing, besides checking the lens for extreme dust and fog at the elements at the sensor/camera side is to test the last element on the outer side of the lens (the side pointing towards the motif).

Usually there is a way to get to this element without disassembling the whole lens.

Then, you will find 3 or 5 screws. Two to fix the lens, three to act as guides in an heliconcentric set of rails. 

With the camera on, and connected to a big screen via hdmi, test and align the correct placement of the last element until it gets as sharp as possible. Check for the boqueh in out of focus areas. It must be circular, not skewed or oval. 

Align the best you can. If at the best it is still bad, then the disalignment is on the zoom/focus block and it will need a professional fix (or from some curious **bleep** like me) to solve it, or a replacement of the part.

Usually dust and scratches on the far side lenses do not affect IQ much (to a point, of course). Only those on the sensor side will.

Usually the problems on the far side do affect alignment and  focus.

Cheers.

Live long and prosper!

[Waddizzle]

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@izzi wrote:

I have been using this lens with my 6D for years (admittedly not regularly - only when I travel), but have recently noticed that things get blurry (moreso toward the outer edges of the image) at 200mm with lower apertures. I can already see the blur through the viewfinder. At higher apertures, photos actually come out less blurry than what I see through the viewfinder. Here are some test images (200m, one-shot AF on the text - I've also tried MF with same results).

f/2.8:

f/8.0 - not as bad:

I'm assuming there's some sort of lens damage - perhaps moisture? Any tips to try out in the field? I won't have access to camera repair for a few months. Thanks in advance!

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Welcome back to the Canon Forums!

You have not provided sufficient information to fully diagnose your issue.  You have not provided exposure settings, specifically shutter speeds.  You were asked indirectly when it was requested that you post an original image for evaluation.  I assume your posted images have had the EXIF data scrubbed away.  Please post your exposure settings, or include the EXIF data.

 Did you have IS enabled?  Are you using any lens filters?  What were the switch setting on the lens?  Did you take your Live View test shot using a tripod?

Testing your gear is just as much a test of the photographers as it is the gear, if not more so.

 Thanks, ahead of time.

[Waddizzle]

“ In case it's helpful to anyone with a similar issue - a heated dry box helped reduce the blur a little, but not for long. I eventually brought the lens in for repair. It did indeed have a busted element, probably from an unlucky knock, which required the whole group to be replaced. “

I just noticed this post.  Thanks, for the follow up.  I’m pleased that you found a solution.