7D focusing issues

[neverhood311]

I bought a Canon 7D about 3 weeks ago and it's paired up nicely with my 17-85mm lens but, for some reason, I'm having focusing problems with my 50mm f/1.4.

When I have the AF set to One Shot and use the full automatic focusing, sometimes it will confirm autofocus but actually be way off. It looks fine in the viewfinder and on the screen but it's pretty bad in the full-size image. Same thing happens when I use the Zone AF mode. However, when I set it to manually select an AF point, it works just fine.

I already know that it's not a camera shake issue since the shutter speeds I'm testing at are 1/125th to 1/320th and I'm not moving the camera forward or backward after it focuses. Also, this lens works just fine with my Rebel XTi. The images are razor-sharp with any AF mode.

So, this is what I do to get it to NOT focus correctly:
*50mm lens set to a large aperture (f/1.4~f/2.0)
*Not a super-bright location, but not really that dark; indoor lighting
*Set AF mode to full automatic or Zone AF
*use my 7D, not my Rebel XTi

Also, in the viewfinder, a point is selected and the camera beeps, but the AF point doesn't flash red. If it DOES flash red, the focus is correct.

Has anyone ever run into this issue before?

[Snarkbyte]

If you haven't already, the first thing I would try is cleaning the contacts on both the camera and the lens. I haven't experienced the exact problem you describe, but you can get erratic behavior from dirty contacts, and cleaning them certainly can't hurt anything or cause issues with the warranty of camera or lens.

[herbert]

Hi Justin,

I've been using the 7D for about 1 year now and am still learning how to get the best out of the autofocus. I stopped using the full 19 point mode early on and rarely use the zone AF. I prefer to use the spot focus or the expanded focus point.

There are several things to be aware of here:

• The auto focus system is optimised to find something with high contrast that it can focus on
• When given the choice the focus system prefers closer subjects
• The focus system uses information from a much larger strip of the image that the little square focus point you can see in the viewfinder
• All your focus points are cross-type which means they spread much further than the focus square in the vertical and horizontal direction

In my experience when using all 19 focus points the camera often finds a subject closer that your intended target. With a narrow aperture the depth of field is so large that this does not usually matter. However with your 50mm prime and a wide aperture the depth of field may be only a few centimeters (check the DOF calculater here: https://www.cambridgeincolour.com/tu...h-of-field.htm). If you check your images that appear out-of-focus see if there is anything else closer than your subject that is in focus.

A classic example where this can catch you out is at a football game. If you try to take a shot of a player note that you have a large field with stripes on it throughout the depth of the image. With all the focus points active the camera can often focus on a line or some of the grass closer to you than your target.

You can test this out by finding a flat area and target object about 10 away. Using manual focussing at your widest aperture, point at the target and take shots as you gradually move the focus from near to infinity. When you review the shots you will see the plane of good focus sweep across the image from front to back.

The reason this may not happen on your Rebel is that only the centre focus point is a cross-type sensor, the others are horizontal only. Therefore the outer focus points will not be able to scan down your horizontal image and find foreground objects since the points can only scan horizontally for focus. It may be interesting to use the Rebel in a vertical orientation and see how it performs since all the points will then be able to scan down the image.

I now prefer to use a single focus point because it means that I am in charge. I think this is as important a step in photography as moving away from the auto-modes towards Aperture-mode, Time-mode and Manual mode and the control of the exposure compensation. Remember that your camera cannot read your mind, it just takes a best guess based on averages. In the long run you will find it more rewarding to take full control and get the shot that you wanted.

Now the only time I use the zone focus mode is when my target entirely fills the zone area and is relatively flat. An example would be the body of a figure at about 5-10m away.

Note that it is not so bad using a single spot to focus given that you can set up the joystick controller to move the point around (You can find this in the custom functions configuration screen.). This means you can look through the viewfinder and move the focal point with your thumb. Or for a quick solution you can just focus and then recompose.

One other tip I have is to shoot about 5 times as many shots as you think you need. With my film SLR every shot used to cost me 20p. On digital, making mistakes is free and the feedback cycle is instant.

Have fun experimenting.

Alex

[koolkat]

I'm also shooting the 7D now, still learning as I've had it about a month & have shot about 500 pictures. Also see the post under "About to pull the trigger.." for additional information. I think Alex has got so great suggestions. Cleaning the camera & lens contacts with a eraser on a pencil is a good idea. My shooting have only use spot, single points or AF point expansion. Mainly AI Servo but may try single shot to see if any real differance in moving subjects. I plan on renting some "L" lens to see how the quality will, may, improve over my Tamron 18x270. Let us know if you continue to have problems, there is an answer out there.

[DoesNotFollow]

I'm surprised that no one has yet suggested using the AF micro-adjust feature of the 7D. Cameras and lenses are made to within certain tolerances with regards to focusing. Your body/lens combination may simply be at opposite ends of their manufacturing tolerance levels. I suspect this is the issue especially because the lens appears to work well with your XTi. Adjusting the micro-adjust for focusing will improve AF speed and accuracy.

While there are many expensive set-ups to configure the micro-adjust, all I did for my 7D was to lean a ruler up against a cardboard box so that I could focus on the side of the box and "read" focus information from the ruler. It's certainly not an ideal setup, and I doubt I achieved a perfect calibration, but it still worked wonders on my kit lens. I would recommend trying this way first to see if it helps, then perhaps invest in something more precise because a lens with f/1.4 has a tiny depth of field and any mis-alignment can be quite obvious. Just be sure to create a separate adjustment for each lens rather than a global adjustment.

If you're interested, there's a pretty in-depth discussion on the topic here: http://www.canonrumors.com/tech-arti...d-other-myths/.

[neverhood311]

I'm surprised that no one has yet suggested using the AF micro-adjust feature of the 7D.

At some point I did a quick micro-adjust for the 50mm but it seemed to be different when I focused on things at different distances. Looking back at it, it was a really hasty test.

Would a lens front or back focus by a different amount based on the distance to the subject?

[Colin Southern]

Would a lens front or back focus by a different amount based on the distance to the subject?

It certainly can. Personally, I gave up on microadjustment a long time ago.

[herbert]

I have also tried micro-focus adjustment and found that my 70-200mm zoom needed different settings for the perfect focus at 100, 135 and 200mm and at different subject distances (i.e. as good as I could get manually at 100% zoom on live view). After playing around with live view and tethered focussing on my tripod for hours I came to the conclusion that the average MFA to get the best results was zero. I suppose that is the compromise that the Canon factory has to make. I found that a misalignment of millimetres with my target was enough to shift the focus more than any MFA setting I wanted to use. Without a test bench setup that I could use to adjust pitch, roll and yaw of both camera and target for perfect alignment I though I would give up and go and take some more photos.

You'll also find that with today's high resolution sensors it is easy to see an apparent misfocus within the accepted depth-of-field for your focal length and subject distance. If you stop pixel peeping and view your image in a realistic scenario (e.g. 6x4 inches at 30cm) then it will look fine. I think Canon auto-focus specification is to hit the focus point on average within 1/3 of the accepted depth of field. This does mean that even a perfect camera will take slightly out-of-focus shots sometimes. Within this tolerance you may not see the fine lines on an angled ruler at the exact focal plane of your target but I don't take photos of rulers anyway. When my people shots are out-of-focus then 99% of the time it is because I did something wrong. I'll work on that problem first.

If you often shoot a subject at a set distance then give MFA a go. Otherwise be very sure you know what you are doing before you override Canon's expertise. If your lens really is that bad then it may be better to send it back to Canon to get recalibrated to factory spec. This should be done within warranty if the problem is genuine and all you should have to pay is postage. Otherwise it should not be more than $100 to reset a lens and camera. It will be more for a collection. Note that contrary to what many believe, a factory calibration will not calibrate your lens to your camera. Otherwise your lens may not work on any other camera or your camera may not work with any other lens. They are reset to what Canon intended from the start so that either will work with any other EF system Canon component within specification (i.e. focussing on average within 1/3 of accepted depth-of-field).

If you have never taken an in focus shot then I suggest this is a problem. If it stops you from sleeping at night then this is also a problem. Other than that then use MFA with caution and make sure you can live with what settings you prefer. I should end this post in a neutral way by saying that some people love MFA and would never buy a camera without it. It's up to you to decide what to do.

Alex

[neverhood311]

You'll also find that with today's high resolution sensors it is easy to see an apparent misfocus within the accepted depth-of-field for your focal length and subject distance. If you stop pixel peeping and view your image in a realistic scenario (e.g. 6x4 inches at 30cm) then it will look fine.

Here's an example of false focus confirmation. I had it set to manual AF point selection, put his face in the center of my AF point, focused, then the camera beeped to tell me it'd focused. I took the picture a split second after it beeped. This is actually a 50% crop. You can imagine that the 100% crop looks worse.

If it were one of my landscape or experimental photographs, I'd just say 'oh well' and get on with it, but when I'm doing engagement photos like this, it's kind of important that the image be in focus. This isn't just a soft image. I'm not that picky. This is completely out of focus and wouldn't even be acceptable for a 4x6 print, let alone larger ones.

It wasn't like this for every shot. I was able to sort through the 200+ photos and find a dozen really good ones that also happened to be in focus. However, this issue came back throughout the shoot.


Also, I mentioned in my first post that in the viewfinder, the AF point had a mind of its own when it came to flashing red or not. Well, I was right. The camera only blinks the AF point red if it's a low light situation where I might not otherwise see the little black rectangle. I also found the custom setting to turn it on regardless of the light.

[herbert]

Hi Justin,

You are right, that is a problem. I would be annoyed if I were you too.

I remember reading some posts about doing a hard reset on the 7D that can fix focussing problems. I can't find the original forum link but found this instead which covers the same points:

http://www.michaelmiles.com/2010/03/...d-focus-issue/

Basically you remove the battery and back-up clock battery from the camera, press buttons a few times to discharge all residual capacity and then leave the camera for an hour. When you put the batteries back in you will have to reset the time and you lose the photo numbering (i.e. it will restart from 1 which may confuse import using Canon's EOS Utility - just format the card to avoid importing duplicates if you use this software). You do not lose your custom camera set-up though. That may be worth trying.

You may want to try setting the custom function C3-II to use focus priority on AI servo mode. However if you were not using AI servo focussing then this will not change anything.

Just in case it makes a difference, I would upgrade to the latest firmware (1.2.5) if you do not have it on your camera.

If the focussing is only problematic on one lens then I would try and get rid of that lens or avoid using it for critical work until you can solve the problem. However you say the lens works on your Rebel and so this seems more like a camera issue. The next step may be to send the camera to Canon.

Hope that helps.

Alex

[DoesNotFollow]

I agree that this does seem to be quite a problem, and, based on the sample picture, the lens should probably be exchanged for another copy outright.

I do want to clarify one thing though; micro-adjustment does have its quirks and exceptions. A big exception is that different focal lengths on the same lens (zoom lenses) can require different calibrations: making it less useful to use micro-adjust on a zoom. For instance, the 70-200mm lens mentioned by <herbert> could front-focus at its 70 and 200mm, but then back-focus in the middle range. A calibration for this would be difficult, if not impossible.

Oddly enough, this can also be a problem for primes, as some of them have rear-focusing systems. By moving the rear element of the lens to focus in and out, it alters the the focal length of the lens when focusing on subjects at different distances. This can complicate micro-adjustment on a prime because, as with zooms, each focal length can need a different calibration.

Your 50 f/1.4 has a front focusing system. Thus, the front element extends and retracts to focus, which changes the focal length. Although this can affect micro-adjustments, the focal length range is fairly small and it may still be worth a try. It would be interesting to see if it needs a significantly different adjustment based on focal distance. If it does, it definitely needs a replacement.

[neverhood311]

I'm trying a hard reset right now. Hopefully that works. In the week following my first post in this thread I did a wedding photoshoot, engagement photos and I photographed an indoor/outdoor dance performance and noticed that I was occasionally getting the same problem (though slightly less pronounced because of the smaller aperture) with my 17-85mm lens, so I think it's a problem with the camera. Lets hope the hard reset works. I guess only my next photo op will tell me for sure. I'll be sure to post the outcome here when I find out.

Thanks for all the help and suggestions thus far!

[rpcrowe]

Hers's a good tutorial on 7D focusing parameters from which I learned quite a bit.
http://www.garyluhm.net/bio/tips_0310.html

[koolkat]

Hi, just reviewed this info on the 7D and its custom functions & features for AF. Good solid information. Thanks Richard for finding & sharing.

[neverhood311]

The hard reset didn't work Here are two shots I took a few minutes ago. Both were taken from a tripod. She was holding really still. I set the camera to Aperture priority mode, f/1.4, ISO 800 and Manual AF point selection. I didn't use the middle point; I used the one that's two over and one up from the center. These are both 100% crops with no touch-up.

The first one IS in focus. I put the AF point directly over her eye. Apparently it liked her eye lashes.
The second one goes without saying. Horrendous. I put the AF point over the hem of her hat. Looking at the in-focus shot, that part looks like it's got more than enough contrast for the camera to focus on.

In both cases, the camera beeped to confirm autofocus.

I'm gonna call up Canon tomorrow I think. I'll see what they can do for me. Canon products have at least a 1 year warranty, right?

[DoesNotFollow]

Are you using any filters on your lens? Shouldn't cause this kind of problem, but might help.

[neverhood311]

Are you using any filters on your lens? Shouldn't cause this kind of problem, but might help.

I've got a Targus UV filter on my 50mm lens and a Canon UV filter on my 17-85mm lens

[DoesNotFollow]

Give it a try without the UV filter. It might help some.

[neverhood311]

Give it a try without the UV filter. It might help some.

I took the UV filter off my 50mm f/1.4. That didn't fix the problem but it did substantially improve the contrast of images with strong backlight. I guess I had a pretty cheap filter installed. Actually I know I did. It came in a two-pack for $18 at Walmart. Silly me for buying a cheap filter.

Last week I was at home in Seattle and went to talk to a family friend about my focusing issue. He's been a sports photographer and photojournalist for the Seattle Times for longer than I've been alive and also happens to own a 7D. So we went through and changed a whole bunch of my custom settings to be more like his. I now use AF point expansion mode and AI Servo instead of Manual point selection and One Shot and I'm getting MUCH better results. Generally 3 out of 4 shots are razor-sharp. I'm still not sure why the old settings gave me such erratic results, but I'm getting good results now so I'm happy. (and so glad I didn't have to send my camera off to Canon for who knows how long.)

[Wendy Stanford]

Hi Justin, I have a 7D and followed the thread with great interest, I'm glad your problem seems to be resolved