AF phenomenon on the 70D: Can anyone explain?

It seems I have the same problem. I live in the Netherlands where shops sometimes sell camera's imported from Germany because they are cheaper there. I will call the shop to ask.

I did some testing some weeks ago, only a few shots, and though it to be a front-focus issue that I corrected with the camera adjustments. Just to find that the next time a lot of images where out of focus, this time back focus. So I have to test it more seriously with a lot of repeated images this weekend.

The issue seems to be not only with fast lenses as I was first alerted by some pictures from the EF-S 10-22mm lens. Later I used the 50mm 1.8 in low light, to find unexplained blurry pictures too.

By the way, the 4th and 5th digit in the serial number is 02 as well.

Jacq

I'm seriously considering upgrading from my almost 4 year old 550 (T2i with about 25-30,000 shots) to the 70D.

I wonder if when I ordered it and asked them not to send a camera with "02" in those positions (I think they were positions 4-5) if they would do it or would I just have to return it unopened if they did?

Myer said:

I'm seriously considering upgrading from my almost 4 year old 550 (T2i with about 25-30,000 shots) to the 70D.

I wonder if when I ordered it and asked them not to send a camera with "02" in those positions (I think they were positions 4-5) if they would do it or would I just have to return it unopened if they did?

Click to expand...

Your profile says you live in FL, why would you order your camera from Germany?

Maybe I wasn't clear.

I won't order it from Germany.

It might be possible that cameras with those flawed serial numbers could be anywhere.

In other forums they claimed that the first two digits are about the production month (in my case 05), and digits 4 and 5 are the hardware revision. If this is true, ALL serial numbers I heard of (they collected them in one forum for comparison) had 02 there, the faulty ones and the good ones. So, there's probably no chance in getting anything else at the moment.

At last in Germany, our warranty laws help us deal with these things - if the product does not meet your expectations, you can give it back within two weeks.

Best regards,

Christian

the 50mm f1.8 is infamous for inconsistent focusing. I clicked on 8-10 replies and didn't see it mentioned, so thought I'd bring it up, but maybe its been mentioned in one of the replies I didn't read. Do a web search on it and you'll find many discussions on exactly what you're describing with the nifty-fifty.

I have two different Canon bodies that do exactly what you're describing, so I don't think the issue is specific to the 70D.

Thanks, it has been mentioned.

However, even before my testing, I was well aware of the downsides of this lens. But that is not the problem here: The 50mm is perfectly usable with any AF field but the middle one, so it can't be the lens. Others experience the same with other fast lenses (85/1.8 and 50/1.4 in particular): a very high amount of OOF images with the center AF field, no OOF images with any other field - just 20 images later under the very same conditions.

This can simply not be explained with an unreliable lens, can it?

Best regards,

Christian

Just to add to the phenomenon, there has been some new development.

Again, I chose a different object (parked car down on the street, especially its high contrast tires), and the problem occured again: many OOF images with the center AF field, none with the others.

Then I switched from One Shot AF mode to AI Servo, and the problem disappeared! I tested it with different objects again, even without a tripod - AI Servo delivers 20 in focus images in a row with the center AF field. Switched back to One Shot, got the old problem again.

Don't know what to think of this crap any longer... Well, gone shooting REAL images over the holidays and report back afterwards...

Best regards, thanks for the very civilised discussion, and have a peaceful and merry Christmas!

Christian

I have 70D and also the 50mm f/1.8 II, but I couldn't reproduce the "bug" related to central AF sensor. I microadjusted focus for the lens to +4. Still, the viewfinder focus with 70D and the "plastic fantastic" lens is consistently worse than with the live view.

I noticed that this lens has a lot of "play" (the mechanical engineering more precise word is "backlash") in the focus ring - low quality plastic gears, hence the nickname "plastic fantastic". That's why I made the following experiment: camera was tethered to the PC then EOS Utility was used to see the Live View image. Set M mode, with f=1.8 and I focused (Quick Focus) then I moved the focus ring a fraction of millimeter, which is possible because the "play" (backlash) mentioned before. Even with that fraction of millimeter the image was grossly out of focus. I also tried to play with the focus ring in AF Servo mode, but the camera quickly moved it back. So it's clear that when you focus in Servo Mode, the camera keeps this backlash under control.

Mirko Taylor said:

I noticed that this lens has a lot of "play" (the mechanical engineering more precise word is "backlash") in the focus ring - low quality plastic gears, hence the nickname "plastic fantastic". That's why I made the following experiment: camera was tethered to the PC then EOS Utility was used to see the Live View image. Set M mode, with f=1.8 and I focused (Quick Focus) then I moved the focus ring a fraction of millimeter, which is possible because the "play" (backlash) mentioned before. Even with that fraction of millimeter the image was grossly out of focus. I also tried to play with the focus ring in AF Servo mode, but the camera quickly moved it back. So it's clear that when you focus in Servo Mode, the camera keeps this backlash under control.

Click to expand...

As it does in One-Shot since they're both closed-loop control systems. Apart from One-Shot halting when the AF sensor sees an in-focus subject, and AI Servo predicting where a moving subject will be, there's nothing to suggest that they're not a single process with those mode-specific aspects.

chbaum said:

Then I switched from One Shot AF mode to AI Servo, and the problem disappeared! I tested it with different objects again, even without a tripod - AI Servo delivers 20 in focus images in a row with the center AF field.

Click to expand...

That may certainly explain the differences in our test results. I use AI Servo for everything (coupled with Back Button AF).

Maybe they made this camera just for me! ;-)

Seriously though, I hope you find your solution soon.

R2

So do I... You as a pro (I guess) - would you leave it at that if you had found a solution *for yourself*? Let's say, I'm able to create the images I want by using AI Servo instead of One Shot - would you stop thinking about a possible fault or bug? Or would it bug you in the back of your head until you contact Canon anyway?

I probably will, because I'm one of those people who get easily bugged (maybe a German thing)... I want to spend 1000 bucks on a product that REALLY works down to its bone (like my TV set for instance). Knowing that some element behaves strangely and can only be tamed by a workaround keeps ringing with me all the time.

But at least, I'll be able to use the camera to its full extent over the holidays.

Best regards,

Christian

Seems like Canon can solve this with a firmware upgrade, hope they release it soon. It would be the smart thing to do since stuff like this can hurt the 70D sales.

chbaum said:

So do I... You as a pro (I guess) - would you leave it at that if you had found a solution *for yourself*? Let's say, I'm able to create the images I want by using AI Servo instead of One Shot - would you stop thinking about a possible fault or bug? Or would it bug you in the back of your head until you contact Canon anyway?

I probably will, because I'm one of those people who get easily bugged (maybe a German thing)... I want to spend 1000 bucks on a product that REALLY works down to its bone (like my TV set for instance). Knowing that some element behaves strangely and can only be tamed by a workaround keeps ringing with me all the time.

But at least, I'll be able to use the camera to its full extent over the holidays.

Best regards,

Christian

Click to expand...

Is the situation focusing on a far away static object using a very large aperture in one shot mode something you would normally do with the camera? Or is it just a made up situation that happens to show a combination of circumstances that you normally wouldn't encounter can produce less than desirable results?

When using a large aperture shooting far away subjects they are normally moving so you would be using AIServo anyway.

If the subject is far away and not moving, wouldn't you normally want to use a smaller aperture to increase the depth of field and overall sharpness of the photo?

Maybe you can think of situation where you want a tiny static subject 100 meters away sharp and the rest of the photo blurry, but, I can't see it occurring very often.

An example of this is that in high speed, high g force transitions, many sports cars will spill oil from the head of the engine into the PCV system and cause a puff of smoke, and an infinitesimal loss of power. Autocrossers and racers who normally encounter those situations install oil catch cans in the system. Does it mean that every BMW that exhibits this behavior is some how defective? Not in my opinion because those are not situations encountered in normal street driving.

Same goes with your camera, is it really a situation that will occur under normal usage?

WilbaW said:

Mirko Taylor said:

I noticed that this lens has a lot of "play" (the mechanical engineering more precise word is "backlash") in the focus ring - low quality plastic gears, hence the nickname "plastic fantastic". That's why I made the following experiment: camera was tethered to the PC then EOS Utility was used to see the Live View image. Set M mode, with f=1.8 and I focused (Quick Focus) then I moved the focus ring a fraction of millimeter, which is possible because the "play" (backlash) mentioned before. Even with that fraction of millimeter the image was grossly out of focus. I also tried to play with the focus ring in AF Servo mode, but the camera quickly moved it back. So it's clear that when you focus in Servo Mode, the camera keeps this backlash under control.

Click to expand...

As it does in One-Shot since they're both closed-loop control systems. Apart from One-Shot halting when the AF sensor sees an in-focus subject, and AI Servo predicting where a moving subject will be, there's nothing to suggest that they're not a single process with those mode-specific aspects.

Click to expand...

Since using AIServo correct the anomaly it would seem to me that Closed Loop/Open Loop debate is far from closed.

With me - definitely not! I'm merely scientifically interested, but I stated in my very first post that in everyday life, this exact setup does not occur with me. At least, I can't imagine a use at the moment - I'm rather into landscapes (higher f-stops), animals (got a 100-400, so no big apertures possible) and nature.

BUT: I wanted to prove the problem to be there when I read about it in the German forums. So I created the setup. The rumors around the bug came from people, however, who actually use big apertures on big distances. One guy for example shoots concerts or indoor children theatre with big apertures in low light. He's quite frakked with his 50 / 1.4 and 85 / 1.8.

Another example that might one day hit me over the head was a guy who shoots distant animals with his 70-200 / 2.8 IS II, a very common usage that I could imagine for myself one day (when I can afford the lens). f2.8 brought up the problem with his 70D, too.

If I went out now, doing my stuff, I promise you, there wouldn't be a problem. But that doesn't mean my brand new camera doesn't have it. So why shouldn't I complain to Canon? The warranty will be gone next November. But according to German law, there's a reversion of proof (or whatever that is in English) after 6 months, so I would have to prove that the problem was there from the beginning. Hence, I'll talk to Canon in January, I guess.

Or wouldn't you?

Best regards,

Christian

I for one can imagine doing landscapes wide open in poor light, and the object doesn't have to be too far away for the phenomenon to be visible either. Together with the overexposing of non Canon lenses when wide open it's a rather serious mess-up for such an expensive camera.

chbaum said:

Just to add to the phenomenon, there has been some new development.

Again, I chose a different object (parked car down on the street, especially its high contrast tires), and the problem occured again: many OOF images with the center AF field, none with the others.

Then I switched from One Shot AF mode to AI Servo, and the problem disappeared! I tested it with different objects again, even without a tripod - AI Servo delivers 20 in focus images in a row with the center AF field. Switched back to One Shot, got the old problem again.

Don't know what to think of this crap any longer... Well, gone shooting REAL images over the holidays and report back afterwards...

Best regards, thanks for the very civilised discussion, and have a peaceful and merry Christmas!

Christian

Click to expand...

Interesting, it is odd that you get consistent (and different) results depending on which focus point you choose. I get random OOF shots with either of my cameras, and changing focus points doesn't seem to have any significant effect. There's no good/bad modes, so that is different than what you're seeing.

At f1.8 its probably not all that practical to use a non-center point, as you'll have a side of the image in focus, and the rest somewhat blurry due to the narrow DOF. Maybe that could be desirable sometimes, but probably not all the time.

I tried using Servo and that did seem to improve the center point performance using about 8 shots as a test, so thanks for the suggestion. As someone said below, perhaps the focus control is too sensitive and the constant adjustments in Servo mode compensate for that.

yellodog said:

I for one can imagine doing landscapes wide open in poor light, and the object doesn't have to be too far away for the phenomenon to be visible either.

Click to expand...

Wouldn't you use a longer exposure to compensate for less light?

A landscape with just a thin stripe in focus?

Ok, please post an example of a photo you've taken like that in the past.

yellodog said:

Together with the overexposing of non Canon lenses when wide open it's a rather serious mess-up for such an expensive camera.

Click to expand...

First the 70D is a mid priced enthusiast camera. Second if you want to use it with other than EOS lenses that is your prerogative, but, Canon wouldn't even guarantee a camera would work with current 3rd party EOS compatible lenses, much less old manual lenses. As you've already been told by Canon the 70D does not support those lenses. If you want to use them you'll have to learn how to compensate for them.

TTMartin said:

yellodog said:

I for one can imagine doing landscapes wide open in poor light, and the object doesn't have to be too far away for the phenomenon to be visible either.

Click to expand...

Wouldn't you use a longer exposure to compensate for less light?

A landscape with just a thin stripe in focus?

Ok, please post an example of a photo you've taken like that in the past.

TTMartin said:

Together with the overexposing of non Canon lenses when wide open it's a rather serious mess-up for such an expensive camera.

Click to expand...

First the 70D is a mid priced enthusiast camera. Second if you want to use it with other than EOS lenses that is your prerogative, but, Canon wouldn't even guarantee a camera would work with current 3rd party EOS compatible lenses, much less old manual lenses. As you've already been told by Canon the 70D does not support those lenses. If you want to use them you'll have to learn how to compensate for them.

Click to expand...

I agree if one is not using a Canon lens they are on their own. Not implying many non Canon lens are not good, or can't get good results.