I just had a play with the same camera/lens combo that was giving problems for me, and today it seems to be working perfectly. Fast and accurate AF every time. I have only tried One Shot, using the Centre Point (same settings that gave problems the other day) so not sure about the other modes yet.
It does hunt around a little when there are two or more different high-contrast areas very close together, but at different distances. It doesn't, however, appear to favour one of those points over another, it just can't decide which one to grab.
Light levels are fairly similar to when I had problems, only subject matter has changed (I was doing portraits when I had problems, now I'm just finding random things to focus on around the room). I can't figure out why it's started working well again, but at least it works. Sometimes these are the worst problems though, the ones that come and go without warning. They can't be solved because when you try to show someone it works fine, then you go out in the field and there it is again.
I hope someone finds a solution for this. For now, I'm gonna hope my camera keeps working (not too happy with a 5 week turnaround from Canon Australia!), and switch to MF if it gets in a tizzy again. Please let me know if there's any help I can give in diagnosing the problem.
Dave0r,
If the focus is OK close up but way off far out, it can indeed be a calibration issue. Try your focus test at varying distances and separate the objects so that there is no possibility of anything but your target-subject being in the center AF zone. As you back off the distance, I would bet that your subject (centered) will eventually be out of focus the farther you are away from it. This was an issue I had with a 1DmkIIN; close up all was great but as soon as the subject was beyond 50ft It would be way off. I'll repeat: it is a calibration issue where it's off as a percentage of the subject distance, not a design defect of the 40D. That's why it works fine up close.
My 40D out of the box needed to go to Canon for a consistent backfocus. Very consistent. Very annoying. Only 7 days without it, but still...
Now that it's fixed, I'm no more impressed by the 40D's AF capabilities as compared to the 30D, and I'm perhaps a bit underwhelmed by what should have been at least slightly better AF (if one is to believe Canon's marketing rhetoric).
Alan321 wrote:
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.
Ok, I get it now!
Alan321 wrote:
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.
Maybe there is a simple bug in firmware logic that occasionally ends up picking the wrong focusing point?
I had this same problem and sent in the 40D to Canon. It came back better but still not right; going back to Canon again next week. The paper which came back with it was missing half the diagnosis but indicated an electrical problem?
It's the same with my 400D.
I'm not able to take a good focused shot with distant objects.
My 70/200/4 and 400/5.6 look horrible on it (while they are beautiful on my 1D).
I have been reading and following the bodies for some time now as I need to purchase a new dSLR. I have sold my 350D (XT), and hoping to move on to a better more capable camera when it comes to AF and IQ.
The 40D since it came, stories swirled around about some makes having AF issues... not good... sure Canon released a nicer looking camera than 20D or 30D, but its AF, which is a very, very important aspect, if not the most important aspect of this, was an issue from what I have been reading all over. I am not happy with that, and certainly will NOT be purchasing a 40D. I do not want to end up with a body that has issues and then be told by Canon "it is within their specs" - slackers!
Sorry, I am going to wait and see what will be coming soon within the next two months - if Canon does not release the "3D" or an upgrade to the 5D, or a "45D" with better focus, I do not know... I may just sell my Canon lenses and move on to a Nikon D300 or D200... for the money you cannot beat its AF and functionality!
For a $1000 camera you would not expect AF to be an issue... if not happy, go get a P&S for $200 or $300 that will take nice pictures outdoors with properly working AF!
There are plenty of sports images being taken with a 40D by people who shoot for a living...check out the sportsshooter site. While it's no 1D series, the 40D has been able to perform very well with everything that I've thrown at it (soccer, football, gymnastics, swimming) in all variations of lighting while I wait for a new set of 1-series bodies. Having also shot hundreds of thoudsands of images with 1-series bodies over the past few years I'll repeat again: the problems reported with the 40D are simple calibration problems and not an inherent AF design defect.
Here's a long distance shot with the poor-focusing-poor-quality (if you believe all that is stated on photo forums) EF 100-400 on an uncalibrated 40D body taken handheld - http://www.bwbrock.com/gallery/2065622_Kwdo8/1/196995179_xtvdD/Large
(NOTE: this 40D did get sent in for calibration as it was off on close subjects)
Early morning, hazy, upper-level soccer kids, relatively marginal shutter speed and the 40D AF tracked as well as the mkII and mkIII. By what I'm reading here, the 40D should have been completely UNABLE to capture shots like this yet I have thousands.
Gochugogi wrote:
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...
Ditto on all of this. AF of the 40D is also much better than my 5D.
Dave, I have been looking into picking up a 40D for quite a while and so just out of curiosity I posted a poll based on this very topic: https://www.fredmiranda.com/forum/topic/631570
I am hoping the results come back with limited AF inaccuracy findings, hopefully these are just isolated cases We'll see.
Bmeister,
I looked at the pictures at your link, all of the subjects are pretty huge compared to the AF boxes and often fill half the frame. Can you show some pictures with subjects being less size than that and with less background blur? I noticed in my 400D that the less background is blurred by the lens (distant object with not very long lens), the more chances I have to focus on background instead of the main object. I just want to see how the AF takes small distant subjects, is that possible?
akovacsi wrote:
AF... was an issue from what I have been reading all over
And for every single post like that, there will have been many more saying that the 40D's AF is very good or better - just like the current threads on the subject here.
I am not happy with that, and certainly will NOT be purchasing a 40D.
Suit yourself - it's your loss...
I may just sell my Canon lenses and move on to a Nikon D300 or D200... for the money you cannot beat its AF and functionality!
Now here's where you're really off the mark: spend some time on Nikonians and Nikon Cafe and you will see loads of stuff about D300 AF problems!
And - as an ex-owner of the D200 myself (it was the D200 that made me decide to become a Canon user!) I can tell you with absolute, unequivocal first-hand-experience confidence that the Canon 30D's AF is better than the D200's: and the 40D is better than the 30D.
Do the sums...
Still, believe what you want - you've obviously already decided to take the Noink route - so perhaps the sooner you do the better.
keithreeder, And - as an ex-owner of the D200 myself (it was the D200 that made me decide to become a Canon user!) I can tell you with absolute, unequivocal first-hand-experience confidence that the Canon 30D's AF is better than the D200's: and the 40D is better than the 30D.
I'm still not sure that I have a calibration issue guys. I'm at work so can't post an example, but I can take a photo of my street sign about 20m away at 55mm F5.6 and it is in acceptable focus.
What frustrates me more than anything is that I don't have any warning when the AF will perform badly and therefore have no confidence in it.
Although it had a huge depth of field advantage my Powershot A95 with its AF point which covers 10% of the image is much more reliable
This really does seem to me like a software issue where it is allowing the use of incorrect focussing points.
I'll take more more long distance shots to see if I can replicate the issue again.
LSerge wrote:
Bmeister,
I looked at the pictures at your link, all of the subjects are pretty huge compared to the AF boxes and often fill half the frame. Can you show some pictures with subjects being less size than that and with less background blur? I noticed in my 400D that the less background is blurred by the lens (distant object with not very long lens), the more chances I have to focus on background instead of the main object. I just want to see how the AF takes small distant subjects, is that possible?
I don't shoot loosely very often and don't do many "tests" with my gear to see what fouls its abilities, but here's the loosest non-cropped 40D shot with a 100-400 I could find (that previous link I posted was mistakenly a 300/f2.8, sorry) and using the upper AF point in Servo mode no less .http://www.bwbrock.com/gallery/2065622_Kwdo8/2/273061840_JA5Kq/Large
Something to keep in mind is that expecting a DSLR, even a 1-series, to grab focus on an object close to the size of the AF-point box in the viewfinder with a cluttered background and foreground is asking a lot of any camera. Having said that, either the 40D focus problems are calibration/adjustment issues or it's simply an error behind the viewfinder. Too many of us get excellent AF performance -- and I especially cite the success I'm having with the 40D for indoor gymnastics (proper lens required) which is a real stress test even for a 1DmkIII.
I've not even used Servo on my 40D yet...I would like to see it nail one-shot focus on still life before I venture to moving subjects. I might email my vendor, but being 4 months old i'm not sure they will be able to help if canon say 'in spec' like they did for Alan.
We'll see.