Are all Canon 70D units affected by the focusing issue or just the first ones?

IntrepidB · Aug 12, 2014

I purchased the Canon 70D as soon as it came out last year, and after months of use, research, testing with different parameters and lenses, I came to the conclusion that the autofocus is defective when I shoot using the viewfinder. I get too many shots out of focus when shooting at large apertures (2.8 and less, and sometimes even at 3.5) no matter how good the shooting conditions are (lots of light, high contrast, steady subject).

I saw countless reports of people with the same issue, and in almost every case of attempted service, Canon denies the problem and returns the camera with the same issue. It is not a matter of micro AF adjustment because the focus may miss randomly, it's not a constant thing as a +2 back focusing.

Shooting with the live view mode gets the focus perfectly, but shooting with the viewfinder does not. The 2 images below I got from recent shots, taken in good lighting and setting the focus point on the eye.
Here is what I get almost every time when using live view mode:

Here is what I get quite often when using the viewfinder:

This video here shows exactly my problem, skip to the 5:00 mark if you are in a hurry: . There are countless reports of this problem on 70D bodies, just google 70D autofocus issue.

I am determined to go to the shop and use this 70D as part of payment for a new camera body. However, apart from this issue I absolutely love the 70D, besides the autofocus issue everything is perfect and I would really like to get another 70D body. I don't mind losing some money in the process if it's going to get me a 70D that focuses properly.

What I didn't find on these countless topics about the issue is if ALL the 70D bodies are affected by this issue, or only the first batches. I want to know if Canon secretly solved this issue in a later revision (they wouldn't inform us because too many people with early models would complain).

If you have a 70D and have some lens with large aperture (kit lens will not count), could you test your camera body? Try shooting someone in good lighting conditions and focusing using the middle AF square in the eye, you can use external flash with infrared for focusing if you want, the autofocus will miss plenty shots. Most of the time you will not notice that the focus is off just by quickly looking on the camera screen, you have to put in the computer to take a good look.

TCampbell · Aug 12, 2014

They don't "all" have the problem but I know several people have mentioned it.

With that said... there's a lengthy thread on Canon's own forum on the topic in which it was discovered that while some cameras have a problem, there are a lot of people "claiming" to have a problem who are simply just using really bad technique and blaming the gear. But it seems that there are also some bodies where the AF calibration is really off.

You can use the AF micro-adjust feature to correct for some of this but you shouldn't have to be too extreme.

With that aside, I've also asked some 70D owners how their viewfinder AF is working for them and they claim they love it. So certainly there are plenty of bodies which are working fine.

I do recommend (very strongly) that you use a focus test chart and good testing methods to measure the extent of the issue (this should also help to get it corrected if you send it in.)

I use a commercially made focus test target, but here's a chart you can download and print on your own printer... along with instructions on how to test: Jeffrey Friedl's Blog » Jeffrey?s Autofocus Test Chart

SCraig · Aug 12, 2014

Do Canon viewfinders have a diopter adjustment?

tecboy · Aug 12, 2014

I use f/1.8 50mm prime lens, and I don't have an issue with my 70D.

snerd · Aug 12, 2014

SCraig said:
Do Canon viewfinders have a diopter adjustment?

Mine do.

SCraig · Aug 13, 2014

snerd said:
SCraig said:

Do Canon viewfinders have a diopter adjustment?

Click to expand...

Mine do.

Sounds to me like a simple diopter adjustment might fix the problem then.

IntrepidB · Aug 13, 2014

SCraig said:
snerd said:

SCraig said:

Do Canon viewfinders have a diopter adjustment?

Click to expand...

Mine do.

Click to expand...

Sounds to me like a simple diopter adjustment might fix the problem then.

Really? I thought that was just to make things sharper for you on the viewfinder in case you had some eyesight problem. As far as I know it has nothing to do with the photo taken by the camera.

SCraig · Aug 13, 2014

IntrepidB said:
Really? I thought that was just to make things sharper for you on the viewfinder in case you had some eyesight problem. As far as I know it has nothing to do with the photo taken by the camera.

You could be right. My thinking was that, per your statement that focus was correct in Live View yet not through the viewfinder, that if the diopter was off and you were focusing so that things looked right in the viewfinder then the focus that was actually being "Seen" by the sensor would be different, or effectively out of focus. I'm not sure now, you could be right.

pdq5oh · Aug 13, 2014

I recently got a 70D (within the last 2 mo). Firmware version 1.1.1. I have the 18-135 and 55-250 STM lenses. I have no issues with either. I also have a 70-200 f4 IS. I have had some issues with that lens. A few times it's claimed focus and the subject was a complete blob. It's also had issues hunting. This seems to be worst at higher magnification, on close subjects. I'm going to return that lens for a Sigma 70-200 f2.8. I rented one of those lenses and had no issues. I also rented a Canon 70-200 f2.8 IS II with no issues. I have a Tamron 17-50 f2.8 non-VC that works fine. Not sure if the 70-200 f4 is the problem or it's the camera but, I'm not "wowed" by the IQ of this lens. I am, however, surprised by the IQ of the STM lenses.
BTW, the diopter does nothing more than adjust the view finder image to your eyesight. It has no effect on actual focus of the image.

TCampbell · Aug 13, 2014

The diopter adjustment is just for your eye... not the camera's focus sensor. This allows those who would ordinarily need to wear glasses with an ability to adjust the viewfinder to their needs. Basically you point the camera at a white wall or the the plain blue sky (something with minimal contrast). I personally find it's actually better to intentionally de-focus the camera for this. Then... while looking at the focus points, turn the diopter adjustment dial until the focus points look sharp (ignore whatever the camera lens is pointed at ... that won't matter).

Basically the camera is supposed to be calibrated so that the focus on the internal focus points (on the floor of the camera), the sensor (at the back of the camera), and the focus screen (on the top of the camera) all agree. If one is focused, they're all focused. So assuming this is true (and it may not be true if the camera is not calibrated correctly at the factory) then "in theory" a focused camera is projecting a sharp image onto the focus screen. The diopter focuses the your view onto that focus screen so that you can accurately determine when the camera is focused.

The 70D does have auto-focus micro-adjustment (in the menu system).

To use this, you'd place the camera on a tripod and place the focus target at the prescribed distance (depends on the lens focal length -- read instructions with the chart). The focus chart will indicate it's target focus point ... typically a high-contrast area at the center of the chart. The chart is typically angled so that part of the chart is closer and part of the chart is farther. Using that prescribed focus point, make the camera focus on that point and expose the image.

Upon reviewing the image, you're looking at the parts of the chart both nearer and farther from the target point and evaluating focus to determine if the chosen focus point has the best focus... or if the best focus lies somewhere else on the chart. If the camera misses focus, you can adjust the AF micro-adjust to correct.

BUT... each lens can be different. On my camera body, the camera is able to recognize 50 unique lenses and can set an independent AF micro-adjust for each one.

There's a menu option to tell the camera to use the same micro-adjust for all lenses... or allow you to set each lens independently.

I know the 70D has AF micro-adjust, but as I've never used it, I don't know if it will be identical to the system on my 5D II and 5D III (I suspect it is the same.)

JacaRanda · Aug 13, 2014

pdq5oh said:
I recently got a 70D (within the last 2 mo). Firmware version 1.1.1. I have the 18-135 and 55-250 STM lenses. I have no issues with either. I also have a 70-200 f4 IS. I have had some issues with that lens. A few times it's claimed focus and the subject was a complete blob. It's also had issues hunting. This seems to be worst at higher magnification, on close subjects. I'm going to return that lens for a Sigma 70-200 f2.8. I rented one of those lenses and had no issues. I also rented a Canon 70-200 f2.8 IS II with no issues. I have a Tamron 17-50 f2.8 non-VC that works fine. Not sure if the 70-200 f4 is the problem or it's the camera but, I'm not "wowed" by the IQ of this lens. I am, however, surprised by the IQ of the STM lenses.
BTW, the diopter does nothing more than adjust the view finder image to your eyesight. It has no effect on actual focus of the image.

FYI - It's probably an individual issue you are having with either or. No problem here with the 70-200 f4 IS II with the 70D.

JacaRanda · Aug 13, 2014

Here you go

IntrepidB · Aug 14, 2014

People, thanks for trying to help, but the 70D issue has nothing to do with micro AF adjustment.

It simply doesn't work because the focus is not always missed in the same way (could be front, back or actually perfect focus) and not by the same amount. Sometimes it is just a little bit of front focus, sometimes it's totally back focusing. It's a random thing and there is no micro AF correction value that will fix this issue.

The way I found around this issue for now is to use the shutter button just for metering and shooting, and I put the autofocus function on that AF-On button on the back. So when taking an important shot I change the camera to the live view mode, use the AF-On button to focus properly, then move back to the viewfinder mode and keep shooting with the previously set focus position as long as the subject doesn't move. Not very practical but at least allows me to reliably get photos in perfect focus.