AF query? (1 Viewer)

Jaff · Feb 5, 2008

Hello all,

I've been noticing lately that on my 40D the AF doesn't get it right alarmingly once too often. The other day I was out at the woods and a Long-tailed Tit popped onto a Gorse bush right in front of me. The center AF point was aiming straight at it and the spot was confirming the AF had locked on but the pictures when reviewed were clearly out of focus (sorry I've deleted them). I only got off a couple of frames so that doesn't help but it's not comforting to know that something like this could happen when it really matters. I've had similar problems on other occasions too, a static subject that the camera says the AF is locked on to but then the image is out of focus in playback. Is this common?

I should point out that it doesn't happen all the time, more often than not it does work but the times it doesn't seem to be are more than I feel comfortable with. Oh and I'm talking without TC here so it's not that.

Cheers all. :t:
Jaff

Ian Latham · Feb 5, 2008

It seems a common fault within certain batches of the 40D (1.03.). The problem was addressed by a newer model (1.04.) but other reported glitches were found to affect file mis-numbering. A firmware was issued (1.05.) and this is supposedly the fix for both reported problems.

What batch number is it Jaff?

I think this problem is a lot more widespread than is being let on (for obvious reasons).

Jaff · Feb 5, 2008

Mine's the latest firmware. Hope it ain't faulty. I'll try and do some tests and post the pics.

Tannin · Feb 6, 2008

You might also consider other factors. There are several things that often lead to the autofocus system not working as expected.

Obviously, there are times when the AF system locks onto something you didn't want it to lock onto.
Poor light, especially diffused light such as you get on overcast days, reduces AF performance
Some birds have plumage that is particularly difficult for AF systems to manage, it seems. Here in Australia, examples include both species of pigmy-goose, some woodswallows (especially Dusky), Grey Fantails from certain angles, Wood Ducks from some angles, even Australasian and Hoary-headed Grebes under some circumstances. There are several others. The common factor seems to be fairly but not completely plain plumage, with a certain texture to it: there isn't much contrast to start with, and the combination of texture and pattern seems to confuse AF systems a lot. I've seen this many times over the years, with P&S cameras and with SLRs, with Nikon and with Canons from 20D and 400D right up to 1D III. There are possibly two causes: very plain, textureless, soft plumage (think Dusky Woodswallow) is featureless and gives the AF nothing to "grip" on; certain small, fine-grained repeating patterns (notably amongst some of the ducks) seem to trick the camera into trying to line up bits that don't actually belong together. I also wonder if plumage patterns (or lack of patterns) in the non-visible parts of the spectrum play a part. Anyway, with some birds, you really should just go straight to manual focus if your first few shots don't seem right.
Time. All cameras, even a 1D III or a D3, need a certain amount of time to lock up an accurate focus. (The IS or VR system also needs a little time to get started.) If you try to fire off shots before the camera has had time to lock in an accurate focus, you get bad shots.
Steadiness. If you are not holding the camera steady on the bird, the AF system never gets a chance to do its job properly. Especially with really long glass, this is yet another reason to use a quality tripod: even if your shutter speed is so high that camera movement isn't a factor, the AF system needs stability too.

There are probably some other factors as well, but it pays to consider the ones above before you panic and think that there is something wrong with your camera.

Tim Taylor · Feb 6, 2008

Tannin, that's a lot of very sound advice there so let's hope Adam has nothing to worry about. Your point about certain plumage types and the length of lens rings very true for me. I was trying to photograph teal and wigeon yesterday in what I thought was reasonable light (at least compared with what we've had recently) and I could focus fine at 500mm but it all went silly at 700mm with the TC in. What I interpreted as a good 'pattern' to focus on on the flank of the bird could easily have hit a ciritcal spacing to throw out AF at 700mm.

Jaff · Feb 7, 2008

Thanks guys.
I reckon poor light was the contributing factor (I think my technique is competent at the very least), I guess I was over-estimating it's capabilities and thinking of it as invincible. Tannin, your suggestions have shed some light on the situation (no pun intended, well maybe a little one!) and I think now I have a better understanding of knowing when I expect it to perform and when it might get confused, after all it is technology and we all know how reliable that is! Happy to report that yday with the sunshine it worked fine and even in some difficult situations. It did have a hiccup with a Little Grebe but I see now this was down to the browness of the bird in difficult surroundings and reflected vegetation on the water, however, I've found Liveview to be a blessing for MF in these situations (especially with its magnify feature) and will use it whenever opportunity permits.

Anyway, once again cheers fellas.
Adam

Tannin · Feb 8, 2008

I am clearly going to have to investigate live view! You are maybe the 3rd or 4th person to say how useful it is for manual focus on these fora in the last week or two. I have never used it for anything, indeed, I'll have to dig the manual out even to figure out how to switch it on. Mind you, back in digiscoping days I never used to use the screen for focusing, on the grounds that you can always get a better focus by removing the camera and focusing through the scope direct, then replacing the camera, but with so many positive comments about using magnified live view here, I clearly should try it. So, Jaff, with any luck, we are both learning something useful in this thread.

Jaff · Feb 8, 2008

Glad I'm being useful.

Oh and I should point out that using it with an IS lens helps tremendously as you can still half depress the shutter and have the benefit of IS to make it easier to focus.

Ian Latham · Feb 8, 2008

Nice one Jaff!! Really glad you've ironed out your camera's idiosyncrasies.:t:

Maybe now you can go back to having some fun with it! Happy days!!:bounce:

Jaff · Mar 24, 2008

Just to give you an update. My suspicions about the camera appeeared to have been justified. I decided to send it off to a repair facility last week and got it back saturday.

Although I haven't tried it yet the notice that came back with it indicated that the focus system had been checked and 'adjusted'. Will let you know how I get on with it when I next go out although the weather here has been rather unpredictable lately (snowy spells mixed with sunny spells!) so hard to say when that might be.

Regards.
Jaff

Jaff · Apr 17, 2008

Just thought I'd bring everyone up to speed regarding my situation.

Since I've had my 100-400mm the AF gremlins seem to be banished (touch wood) and I assure you I have not done anything differently from before. Very odd.

With crossed fingers (makes typing a lot harder though...LOL!)
Adam

gmax · Apr 17, 2008

Jaff said:
Just thought I'd bring everyone up to speed regarding my situation.

Since I've had my 100-400mm the AF gremlins seem to be banished (touch wood) and I assure you I have not done anything differently from before. Very odd.

With crossed fingers (makes typing a lot harder though...LOL!)
Adam

Touch wood, and wish you some sunny spells

goodallian · Apr 19, 2008

Hi Jaff, my first post so please bear with me. Glad to see that you have had your problem sorted.
My 40D (6 weeks old) has had similar problems with the addition of front focussing on many of my shots. I was reluctant to blame the camera at first but having read your Thread I have done several field tests on birds of varying sizes and distances and more recently using static objects where the centre point AF square confirmed focus every time but images were poor and unacceptable.
I used a Canon 300mmf2.8 IS + 1.4x on a gimbal mounted tripod alternating with my older 30D and using identical settings in camera. I have not done any post processing save coverting from Raw. The differences were striking (see attached example).
Warehouse Ex were informed and have agreed to collect the 40D on Monday but whether replacement or repair they wouldn't commit.
My thanks to the Forum and all its contributors for the informative and interesting debates.
Ian Goodall.

carpy1 · Apr 19, 2008

hi all just to add my pennies worth on this topic i purchased a 40d 4 weeks ago after a few years using a 35od combined with the bigma lens the very next day i was out with it taking shots of raptors using the centre spot focus point and was finding the images on the screen out of focus i tried multiple settings and the lighting conditions were perfect but the images were all out of focus .The next day i arranged to return to the store i purchased the camera and after explaining my concerns was met by a canon rep who proceeded to test the camera trying different settings himself and agreed that the images were not as one would expect the camera was exchanged and i am more than happy with the results i am capturing with the replacement . It would appear that there has been some autofocus problems with some cameras .

postcardcv · Apr 20, 2008

goodallian said:
I used a Canon 300mmf2.8 IS + 1.4x on a gimbal mounted tripod alternating with my older 30D and using identical settings in camera. I have not done any post processing save coverting from Raw. The differences were striking (see attached example).
Warehouse Ex were informed and have agreed to collect the 40D on Monday but whether replacement or repair they wouldn't commit.

Those photos show very clearly that there is a problem with your 40D, I would guess that it is front focusing and doing so quite dramatically. Hopefully WHE will get this sorted quickly for you.

Jaff · Apr 21, 2008

Sounds like the problem I was encountering Ian.

It's a sunny day and I'll be off to Martin Mere shortly and as there'll probs be little in front of the hides I'll wander through the captive wildfowl area and see if my problem has truly been resolved. Will let you know how I get on.

Jaff · Apr 22, 2008

The performance of mine has definitely improved IMO. I'm actually finding it works best using AI Servo all the time but even in One Shot it seems to be better. I supose with hindsight I should've kept the oof ones to put on here rather than delete them, d'oh!

I wonder if people will still have problems with new cameras later in the year. Should be a different batch then.

Anyway, I'm happy as Larry now so thanks to the input on this thread.
Adam

goodallian · May 1, 2008

A quick update on my 40D:

1. Had to send the camera back to WExpress myself 'cos their Courier firm (having said they called), never collected. (now £20 owing me from WE)

2.Phoned WE today (having not heard anything for a week) and was told it had been sent away for repair to Canon as it was 12 days outside their 30 day limit and it could be up to 6 weeks before return!!

3. The phrase "please keep me informed of your decision" in my accompanying letter with photos was clearly overlooked.

Moral: extensively test all new gear A.S.A.P if you expect a replacement!

goodallian · May 10, 2008

Final (I hope) update:
1. £20 postage refunded by Warehouse Ex.

2. The 40D arrived unexpectedly on Thursday 8th, some 15 days after WEx originally received it, having been dispatched to them from Canon and I am happy to report that after extensive testing yesterday "in the field" including swapping camera bodies with a colleague on the 300f2.8+1.4x and his 500f4, I believe the AF problem has been sorted. The repair information docket simply had the "mechanical repair" and "service clean and check" boxes ticked but not the "adjustment" box. Printed photos and PC images appear now as they should with such expensive glass, but I will definitely be keeping the 30D!

Thanks for all the interest shown.
Ian

Cashie · May 21, 2008

After reading all this I thought I would just tell you about my experience with these two cameras.

The 30D is an excellent alrounder with all my lenses but my 40D only seems at it's best in very good light, where my 30D is more fogiving.

Using the 40D with the 400 5.6, 100-400, & 500 f4 is very good but not as good as with the 30D from which I always get more keepers.

So in my experience of using these two bodies, I prefer the 30D.
Any thoughts ?

AF query? (1 Viewer)

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