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DPChallenge Forums >> Hardware and Software >> Canon 70-200 f4 L glass - backfocusing nightmares!
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08/28/2006 03:58:18 PM · #1
On the 16th August we bought a new camera body and a new lens (we needed the new body in order to have one each as we sold the Nikon D70 at the beginning of the year - we'd deliberately been waiting until shortly before the next overseas trip to buy the Canon replacement). We went for a Canon 350D (for me as I have smaller hands than Pete who can hardly hold it) and a 70-200 f4 L glass lens.

Can I just say "L glass" again please? GRIN!

So we finally made time to test them both this Saturday by visiting our nearest RSPB reserve in Rye Mead. (I joined the RSPB when we went to Wales in June - I'd been intending to for ages as I really want to contribute to the conservation work they do particularly in terms of buying land to ensure that vital habitats are preserved).

I was using the new camera and the new lens and I didn't get a single sharp shot from the session! This lens is known for it's sharpness (as are all L glass lenses) so I assumed I must be the weak link. Often the subjects were moving and I'm awful at panning so that might account for some of the bad shots but a few shots were of some swans grooming in the shallows RIGHT in front of the bird hide we were in! The camera speeds were high enough that camera shake could not be a factor - not to mention that the lens was braced on the hide window ledge.

Sheesh!

So what do do? Further testing, we decided!

On Sunday we took a trip to Kew Gardens and decided to split the new body and lens up. I used the new body with our 100mm macro lens (which I'd used for the very first time on our previous trip to Kew a few months back) and Pete stuck with our existing body, the 20D and the new lens.

Oh and we bought annual joint membership to Kew too! Very Happy

So... my shots were just fine meaning the 350D body was OK - which is what we had already figured.

Pete's shots using the new lens weren't so hot. And we had taken some shots that were taken especially to test the issue too - the camera was perched solidly on a concrete step and Pete used the timer delay to ensure no camera shake was introduced in pressing the shutter or in camera movements. I sat a few metres away. I held my arm infront of me with my watch face aimed in his direction. He used the autofocus to focus on my watch. When we looked at the shots back at home the watch was out of focus but the sharpness of my (clothed) bosom and hair several centimetres further back was incredible!

So there was the pin sharpness we had hoped for but not where it should have been! We had a lens with backfocusing problems! AAACK!

We Googled and quickly discovered that many of Canon's L glass lenses suffer from backfocusing until they have been recalibrated by Canon and this lens in particular seems to be prone to it. The solution seems to be either to return it and keep swapping until you get one that's OK or to send it to Canon for recalibrating.

Since we were still within the 30 day no questions returns policy we went in to see our extremely helpful Jessops store manager about it.

He'd not heard of backfocusing either but I explained to him how we'd tested it and what we'd found online about it too.

I said my preference would be to swap it for a new one as soon as possible so that we could test the next on within the 30 day period too and proceed from there. OR to return it if necessary and buy another one if swapping was not possible.

He said he knew there was one in stock in the two nearest branches and we could either go and collect/ swap today or he could collect one on Thursday when he was working in one of those stores and bring it back to our local store then. When I expressed worry about that eating into the 30 day returns period he immediately said not to worry about that and that he'd extend it if necessary.

He rocks!

In the end we decided to whizz down to the Finchley Road branch and do a swap straight away which we did - no problems, very straightforward.

Pete tested the lens as soon as we got home by taking pictures of a ruler. He could then focus on a specific number along the rule and easily see whether the focus fell where it should or further forward or behind. He did a comparison test using our macro lens too.

Well... good news is the macro lens focuses just where it ought to.

Bad news is that the second L glass doesn't.

Phoned the Jessops man back to update him and he was brilliant again - he said he'll get hold of the lens that the third local store had in stock tomorrow and call us and we could go in and swap again. I suggested we do the testing right there in store - we'll take our camera, CF card, laptop and ruler and can both test it immediately and also SHOW him the problem so he can truly see it, not that he's doubted us in anyway. He was keen on that idea - I think in order that he could learn about this issue that he hasn't come across before either.

So that's where we're at!

We'll keep you updated!
08/28/2006 04:00:42 PM · #2
Wow, what a PITA.

I have to say, my 70-200 f4L works just fine with my 10D.
08/28/2006 04:02:29 PM · #3
Come on, Glen... gotta repeat the comment you put on my blog? Pretty please? :D
08/28/2006 04:04:31 PM · #4
why.. so I can have Canon people jumping down my throat for a month?

:)

Still.. that *IS* what you get for going Canon
08/28/2006 04:07:53 PM · #5
my 70-200/4 L needed to go back to Canon for backfocussing. I got it back 3-ish weeks later, but I never really liked it. They fixed it, but the lens did seems to have a hard time locking on from time to time. I figured it was due to the not-as-good focussing system of the 300D. I sold it (for that reason as well as others). Good news is I got more for it used than i payed for it new (got it on sale).

:)

Message edited by author 2006-08-28 16:09:10.
08/28/2006 04:17:07 PM · #6
Originally posted by Artyste:

why.. so I can have Canon people jumping down my throat for a month?

:)

Still.. that *IS* what you get for going Canon


Hugs! You're so adorable!
08/28/2006 04:19:00 PM · #7
FWIW, I've noticed that my 70-200f4 is not nearly as good at focusing on Andrea's 300D as it is on my 10D. The first time I used it on that camera, I ended up manually focusing for a good part of the time. On my 10D, the 70-200 fairly rocks.
08/28/2006 04:21:31 PM · #8
I read a lot of backfocus horror stories about this lense before I bought it. Then I bought it and took a bunch of shots of sailboats on a lake. All the waves behind the boats were tack sharp, none of the boats. Thought I had suffered the fate I had read about.

I hadn't. I suffered the fate of two Iced Venti Americanos, the subsequent shaky hands and the ill effects when hand holding a telephoto dialed up to full zoom. Autfocus with a little shake in your hands trying to nail a small subject was the culprit.

That's just my experience with it. Since that first day I've not had any problems because I'm aware of how sensitive a piece of equipment it is. I make sure I am steady else I use a tripod.
08/28/2006 04:32:13 PM · #9
We've checked it on both 350D and 20D and we've done comparison checks with other lenses. We're fairly confident it's not the camera bodies in this case.

We did ensure that camera shake was not the culprit by taking some shots on tripod/ very solid base and using the time delay shutter release to eliminate nudging.

Shutter speeds were also kept high.


08/28/2006 04:34:40 PM · #10
The frustrating thing is that the pictures from the 70-200 really are fantastically sharp - just in the wrong place!

To show the problem I took a few test shots - first with our 100mm f2.8 macro (which works like a dream):

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And then with the 70-200L - gloriously sharp, but bear in mind that in both pictures I was focusing on the 15 inch mark on the ruler.

' . substr('//static.flickr.com/72/227494722_23d0dc9ce1_t.jpg', strrpos('//static.flickr.com/72/227494722_23d0dc9ce1_t.jpg', '/') + 1) . '
08/28/2006 08:42:36 PM · #11
Ok, I don't think we needed to write a whole saga on the backfocusing issues and blame it on a type of lens.

Random lenses will come from the manufacturer with backfocusing issues. Those lenses need to be sent back. As we have seen from thousands of test shots, there is nothing wrong with 70-200 F4 L lenses.
08/28/2006 08:45:02 PM · #12
Originally posted by ganders:

The frustrating thing is that the pictures from the 70-200 really are fantastically sharp - just in the wrong place!

To show the problem I took a few test shots - first with our 100mm f2.8 macro (which works like a dream):

' . substr('//static.flickr.com/93/227494721_629e77904d_t.jpg', strrpos('//static.flickr.com/93/227494721_629e77904d_t.jpg', '/') + 1) . '

And then with the 70-200L - gloriously sharp, but bear in mind that in both pictures I was focusing on the 15 inch mark on the ruler.

' . substr('//static.flickr.com/72/227494722_23d0dc9ce1_t.jpg', strrpos('//static.flickr.com/72/227494722_23d0dc9ce1_t.jpg', '/') + 1) . '


Have you checked the AF point you are using? Perhaps you are focusing with the center and the camera is focusing with the top center? I'd check the AF points that are being used by the camera.
08/28/2006 09:12:48 PM · #13
Just in case it helps any...

Focus Testing
08/28/2006 09:48:40 PM · #14
yeah don't test autofocus with a ruler. Use different distanced items with contrasty flat surfaces facing you.
08/29/2006 03:34:53 AM · #15
Kevin, that was the first thing I checked on the first day of shooting and again during the "tests".
08/29/2006 03:42:22 AM · #16
Originally posted by kyebosh:

yeah don't test autofocus with a ruler. Use different distanced items with contrasty flat surfaces facing you.

Umm... I'm not sure what your logic is here. Doesn't autofocus work on a flat, strip of metal with high contrast line markings on it?

In fact, aren't markings on a steel rule "different distanced items with contrasty flat surface"?!

Message edited by author 2006-08-29 03:43:39.
08/29/2006 08:24:29 AM · #17
I bought mine used and it backfocussed like hell. Had to send it in to Canon to have it recalibrated.

The 70-200 f/4 is a great lens, but there is a history of bad calibration with lens. Lots and lots of examples on the web.
08/29/2006 08:46:37 AM · #18
Mine was the same. Bought it used, and backfocus was horrible. I sent it to Canon for calibration, and the lens came back amazing. It became my sharpest lens. I only sold it recently to trade up to the 2.8 IS. It was very hard to part with, but hey...IS rules!

Just send it to Canon and it'll come back tack sharp. It is truely an amazing lens for the size and price.

Good luck!
08/29/2006 08:54:31 AM · #19
I recently (about 3 months ago) got a 70-200 F4 but have not checked it for backfocus. Guess it's time! If it needs to go to Canon for calibration how much does it cost and how long does it usually take?
08/29/2006 09:26:44 AM · #20
Originally posted by kawesttex:

I recently (about 3 months ago) got a 70-200 F4 but have not checked it for backfocus. Guess it's time! If it needs to go to Canon for calibration how much does it cost and how long does it usually take?


Roughly $100. Mine was back within 2 weeks.
08/29/2006 09:28:42 AM · #21
I don't have time to send it to Canon for recalibration - we're travelling in a couple of weeks on holiday - we timed our purchase to give us a month of practice and testing before the trip.

And whilst I'm happy to send products to them for repair or calibration after some use frankly it bugs heck out of me that they seem unable to ensure that all or at least the vast majority of this lens are properly calibrated before being sent out for sale!

I thought one had to legally ensure products were fit for the job they were being sold for?!

Kawesttex, unless you always manually focus you'd have noticed immediately if your lens was backfocusing - every picture we take using autofocus is focused at least one centimetre, often several further back than it should be! It's impossible to miss!

Thanks for the support folks, we'll let you know!


08/29/2006 09:39:55 AM · #22
Originally posted by Kavey:



Kawesttex, unless you always manually focus you'd have noticed immediately if your lens was backfocusing - every picture we take using autofocus is focused at least one centimetre, often several further back than it should be! It's impossible to miss!


Thanks Kavey, apparently mine doesn't have this problem since the majority of the time it's in autofocus.
08/29/2006 09:56:59 AM · #23
Originally posted by Beagleboy:

Originally posted by kawesttex:

I recently (about 3 months ago) got a 70-200 F4 but have not checked it for backfocus. Guess it's time! If it needs to go to Canon for calibration how much does it cost and how long does it usually take?


Roughly $100. Mine was back within 2 weeks.

Although if you only bought it 3 months ago (assuming you got it new) then it should be a warranty repair and thus free, no?

However, it shouldn't be the default answer to buy a lens and then immediately send it to the manufacturer to get it working properly - especially at the 'pro' end of the scale.
08/29/2006 10:04:14 AM · #24
I should have been a little more informative, I got the lense used and yes I agree you shouldn't have to send new items in for calibration or repair on a repeated basis. I am in the electronics calibration business and you'd be amazed at the amount of commercial electronics equipment that doesn't meet full specifications first time through and require warranty alignment or repair.
08/29/2006 10:33:08 AM · #25
Not amazed, just disappointed :-)
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