I had huge problems with mine. I had it checked by Canon and was assured that it was within spec, and so I sold it. It was a useful learning exercise but the camera AF was inferior to my pro cameras (as most would expect) and even my 20D (which ought to be a surprise). It was eratic/unpredictable in all modes of operation and I think the Canon tech that tested it was blind but several Canon Australia reps also said it was as good as can be expected for a camera of that class. Heap of junk as far as I was concerned. Unable to track walking people. Unable to stay locked on a subject. Way too long (6 frames) to regain focus. etc.
Interesting this has been mentioned. I had some trouble with mine yesterday and ended up switching to Manual Focus for most of my shots. It was fairly low window light, but I was using my 85mm f1.8, which let's plenty of light in, and usually focusses very well in almost any light level. I also used only the center AF point, which should be the most accurate and sensitive of them all. The AF seemed to just accept anything that was "close enough" to sharp, even though it was clearly not on focus.
Does anyone know where in Melbourne (Australia) I should go to have it checked by Canon?
They just took a month to fix my 18-55IS under warranty - decided to replace my lens - then sent me an 18-55 Non IS by accident (to brisbane). So that had to go back to sydney and another lens come to Brisbane. They are absolutely hopeless and useless on the phone
I raised the similar AF question about my 400D. Guys here answered that it's because the AF sensor being large.
I have the same problem with focusing on subjects if their surroundings are brighter and more contrasty than the part of the image you're focusing on. In your case it's the black cat with the dark fence. I think I would get the same result. But before this thread I heard no one complaining on this. As an addition, I cannot focus on a distant subject, if it's not much bigger than the AF point square or not brighter than the surroundings, it simply hits the background. Again, I'm using a 400D.
Would be glad to see what solution we'll find (except buying a mark III of course)) )
LSerge wrote:
I have the same problem with focusing on subjects if their surroundings are brighter and more contrasty than the part of the image you're focusing on. In your case it's the black cat with the dark fence.
If the 40D cant see decent contrast between the bottom fence post and the shadow and grass below it then that is pretty poor.
I don't think 20/30D users seem to have these problems as often - their cameras will be slow/fail to lock focus, whereas our 40D's just lock focus on anything - usually the wrong thing.
I've used a 40D since 9/2007 and haven't had any AF problems whatsoever. Amazingly nimble and accurate. On the other hand, both my 10D and 20D were very unreliable in low light. However I rarely practice lock-AF-recompose. I use the joystick to select individual AF points. Wish I had ECF. Was a lot faster.
Scroll to page 10 to see how large the AF sensors actually are - they are mostly touching each others. On the other hand, the diagram on page 11 is somewhat confusing and would lead you to believe that the sensors are much smaller than the actual circuit diagrams shown on page 10.
However, if what is shown on page 10 is true, it is no wonder that it is hard to get the AF spot on, in an area where there are more contrasty areas around, even relatively far away.
When I look at my 30D in the sensor clean mode, at the bottom of the mirror box, I see there holes corresponding to the AF sensors. They are mostly distinct except for the NE sensor having a long hole common with the SE sensor, and likewise for SW and NW sensors.
If the 40D diagram is accurate, the central sensor should not have a separate hole in the mask (in the bottom of the mirror box) but rather there should be large hole in the center, catering for the central and top and bottom sensors. Likewise for the rightmost three sensors, there should be one large hole, and same for the leftmost three sensors.
Can anyone with a 40D check this and report back?
If this all is true, 40D has worse sensitivity for small detail in AF than 10D/20D/30D/etc. And that is bad news, to me at least. So far it has prevented me from upgrading my 30D to a 40D, even though there are quite many features that I would love to have.
So it focuses like a mkIII? Just kidding. Your 40D body needs a basic calibration that was probably missed during production; it happens. If you got it new, you have a warranty so send it to Canon with the sample problem shots on a CD and written description of the problem (i.e. it's back-focusing, and does it in single AF or Servo or both?).
This should be a quick turn around...figure one week out of service or less than a week if you're a CPS member. I have two 40D bodies and they are spot on and AF is *almost* as robust as the 1DmkII. The problem you are having is NOT an inherent deficiency with the 40D AF system.
Here is why I'm a little peeved with the autofocus. These are just two examples of 18-20 shots in the sequence. ALL were OOF. Shutter speed 1/3200 at f5.6 with Canon 500mm F4 IS on tripod. IS off. Have other sequence with ski jumpers - similar shutter speed, IS ON, center focus (yes, on subjects). Both shots below are 50% crops. And there was nothing else in the frame to compete with the autofocus points. Now still with user error, I'd expect to get at least one semi-sharp exposure. Not so. Arghhhh. Maybe time for a 1 series...
Bmeister, on top of the 1D3 mess my 40D experience put a huge caution on any future Canon DSLR purchase. I'll not buy anything with three months of actual release, in order to hear about any flaws before I buy them. With my 40D I showed Canon a CD of images and carefully explained the problem but they tested it and said it was within spec. So much for their specs. In my experience with three cameras and a lens your suggested turn-around time is certainly not applicable in Australia. I allow 5 to 12 weeks, with the average being 8 weeks !
astrolucida, the AF sensor circuits are relatively close to each other but when you allow for the way the AF lens system spilts the image up and separates it into different phases they are in fact not so close. Compare the top leg of one sensor with the top leg of the one above, rather than to the bottom leg of the one above, to get a better idea of what I mean. The outer sensors are relatively closer than they used to be on the 20D/30D because the diamond pattern has bulged a bit, but that just makes tracking with the centre sensor even harder. Either that or the centre sensor is less selective than it used to be. Neither is good.
The sensors do cover an area (or rather a cross) that is larger than the indicated boxes in the viewfinder but they are quite separate from each other, or at least from the centre sensor. However, the centre sensor has extended parts that are meant to work only for low light and there is also a separate diagonal cross sensor. Some of the stuff my camera focused on was closer to the next sensor than to the one I had selected and yet I had selected a single sensor. It seemed as if the camera had a mind of its own as to which sensors to use and when.
The result was that a subject had to be quite large in the frame before it could be focused reliably no matter how good a contrast edge it offered to the focus system. Most people do not have this problem, which makes me think it was an intermittent fault or construction inconsistency between samples, much like the response they got with the 1D3. Maybe they shared too much of the same technology. Whatever the reason, the AF was far worse than my other cameras even after being serviced. People here suggested I should not expect the 40D to be as good as my 1D2 or 1Ds2 but they could not justify why it should be worse than my 20D.
rosscova, if Canon have an office in Melbourne then take your camera there and they will ship it to the techs at Sydney. From Sydney it will be shipped back to you but I've never had a turn-around time less than 5 weeks. And guys in the US or UK get a camera and heap of lenses done in a couple of days. Amazing ! Maybe it's different for CPS members.
Bmeister wrote:
So it focuses like a mkIII? Just kidding. Your 40D body needs a basic calibration that was probably missed during production; it happens. If you got it new, you have a warranty so send it to Canon with the sample problem shots on a CD and written description of the problem (i.e. it's back-focusing, and does it in single AF or Servo or both?).
I think if i sent it to canon they would say there is no problem - look at these test shots for fine focus (back and front) - center point is on the herron bottle
It seems though in real world shots where the subject is not so large in the frame and there are closer contrasty objects the camera uses a focus point other than the one selected, even though it confirms focus on the center point.
Bmeister wrote:
This should be a quick turn around...figure one week out of service or less than a week if you're a CPS member. I have two 40D bodies and they are spot on and AF is *almost* as robust as the 1DmkII. The problem you are having is NOT an inherent deficiency with the 40D AF system.
Canon Australia is really slow for consumer service, it took them a month to replace my kit lens, and then they sent me the wrong lens by accident.
Also, i'm sure its not a dud lens as my original kit lens had this behaviour, my brothers 17-85 has done the same thing (on my camera), and my new 18-55IS is doing it...so it is definately the 40D.
My 40D sometimes behave that way too. In fact the 20D Af although not as fast seems to be more accurate... Question is : Can this be fixed by an update download? And if so will Canon release the fix fast?
