40D single AF point performance

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Archive 2007 · 40D single AF point performance

Daan B
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p.1 #1 · 40D single AF point performance

For shooting portraits I use a 5D. I don't use the focus recompose technique since I shoot a lot at f/2.8 and wider. Instead I use the single AF point technique. In portrait mode (vertical shooting) I must use the most right AF points to get the focus on the eyes. But since these are not cross type sensors, I do find them unreliable from time to time (depending on the situation). I shoot a lot with available light and reflectors only.

I noticed that all of the 9 AF points of the 40D are cross types. So I was wondering when using the most right single AF points, does the 40D have a "better" AF performance than the 5D? "Better" as in more reliable, not necessarily faster...

Another thing... I really like the minimal effect of the 5D's AA filter. When using lenses like my 85L II and 135L, most of the time I don't have to USM (I shoot RAW). How would the 40D compare to this?

Any other things that I have to be aware of when using a 40D next to a 5D for shooting portraits?

Thanks!

Dec 06, 2007 at 06:25 PM

John Ferguson
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p.1 #2 · 40D single AF point performance

The 40D focus system is excellent, better than the 5D, but the files are noticably softer than the 5D. The 5D II will most certainly have the improved 40D focus system (or better).

Dec 06, 2007 at 06:46 PM

Il Medico
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p.1 #3 · 40D single AF point performance

Had the same issue with my 30D. The outer focus points were unreliable at fast apertures.

I have no such problem with my 40D. Accuracy of all the individual focus points is excellent IME.

As for softness or sharpness, I can't say. If needed I sharpen in post so I don't see it as an issue.

The RAW files seem to be very nice.

Gene

Dec 06, 2007 at 07:04 PM

Sam Bennett
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p.1 #4 · 40D single AF point performance

Absolutely. The focus accuracy/consistency is better on the off-center points even without f/2.8 lenses, just even better with them.

Dec 06, 2007 at 07:11 PM

abqnmusa
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p.1 #5 · 40D single AF point performance

configure the 6 extra AF points for center 5D using the custom function. Then the 5D focus & AI servo will equal or out-perform the 40D center focus, especially with AI servo. Or at least that is what I see with my 5D & 40D. Both camera have good focus ability.

I also pfefer to switch autofocus points, rather then focus/re-compose

Dec 06, 2007 at 07:31 PM

Alan321
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p.1 #6 · 40D single AF point performance

Daan B wrote:
I noticed that all of the 9 AF points of the 40D are cross types. So I was wondering when using the most right single AF points, does the 40D have a "better" AF performance than the 5D? "Better" as in more reliable, not necessarily faster...

The trouble here is that focus speed is an important component of focus reliability. There's no point being more accurate if it always takes longer to achieve than you are willing and able to give it. The result will be poorly focused shots. Focus reliabilty is a useful balance of accuracy, speed and consistency or repeatability.

In my experience the 40D AF is unreliable or at least inconsistent. Too often it grabs the wrong subject even when a single AF sensor is specified and is on target and the target is adequate in terms of contrast. I suspect an AF algorithm defect in which the extra long sensor elements for detecting a highly-defocused condition are used when they should not be. If it isn't that then there must be a technical fault, and yet Canon reckon it is performing within specs. Those specs must be pretty loose.

I don't have personal experience of the 5D needed to address your other questions.

- Alan

Dec 08, 2007 at 06:51 PM

k nakamatsu
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p.1 #7 · 40D single AF point performance

Alan321 wrote:
Daan B wrote:
I noticed that all of the 9 AF points of the 40D are cross types. So I was wondering when using the most right single AF points, does the 40D have a "better" AF performance than the 5D? "Better" as in more reliable, not necessarily faster...

The trouble here is that focus speed is an important component of focus reliability. There's no point being more accurate if it always takes longer to achieve than you are willing and able to give it. The result will be poorly focused shots. Focus reliabilty is a useful balance of accuracy, speed and consistency or repeatability.

In my experience the 40D AF is unreliable or at least inconsistent. Too often it grabs the wrong subject even when a single AF sensor is specified and is on target and the target is adequate in terms of contrast. I suspect an AF algorithm defect in which the extra long sensor elements for detecting a highly-defocused condition are used when they should not be. If it isn't that then there must be a technical fault, and yet Canon reckon it is performing within specs. Those specs must be pretty loose.

I don't have personal experience of the 5D needed to address your other questions.

- Alan

That's funny - I've had no problems at all using the center point and outer points. The focusing has been consistent (even in low light for concerts and dance events) and is a noticeable improvement over my 20d. Kind of jumping the gun to say that there's a defect based solely on your own experience don't you think? Have you had the camera checked by Canon? And have you had any other 40ds?

I would say that the 40d's focusing is faster than my 5d too. I haven't performed any kind of tests or anything - this is just based on real world experience shooting events.

Dec 08, 2007 at 07:56 PM

Conner999
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p.1 #8 · 40D single AF point performance

My experience with the 40D during a test was that the AA filter on the 40 is thicker than the 5D's and will require more USM with comparable lenses on the 5D.

Dec 08, 2007 at 08:02 PM

Alan321
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p.1 #9 · 40D single AF point performance

k nakamatsu wrote:
Kind of jumping the gun to say that there's a defect based solely on your own experience don't you think? Have you had the camera checked by Canon? And have you had any other 40ds?

No, not jumping the gun. My experience is valid. That of course does not mean that all 40Ds are bad but it certainly means that mine is. I had it serviced by Canon and they disagree. Therefore I can only conclude that their 40D specs are somewhat looser than I would like to see or, as with the 1D3, they don't yet acknowledge a real problem.

My 20D was slower but more consistent in its AF thna is my 40D - both in One Shot and AI Servo modes. My 1D2 and 1Ds2 are naturally better. No I do not say that a 40D should perform as well as a 1D2 or 1Ds2, just that it should perform consistently and also better than my 20D.

I do harp on about the 40D AF problem but Canon had their chance to fix it. I had it for 4 days and then they had it for 5 weeks and now I have it back with no changes made. Focus tracking in AI Servo with the centre sensor and One Shot focus with the central sensor are too inconsistent. Fair enough that if AF drifts off target it should be back on target within two frames. Mine can take five or six frames (almost one second) to get back and then drift off again very quickly or just overshoot.

My 40D is not useless (far from it) but nor is it as good as it should be even for a non-professional camera. I think it is fair to let people know that 40Ds may be less than perfect in either their QC or design. I don't know which and probably never will. By and large the 40D user base is not domnated by professionals who demand very accurate AF with large aperture lenses, and so even if the 40D had a general AF problem Canon will never be flooded with complaints as much as they were for the 1D3. Note that the 1D3 problems were all said to be the fault of the photographers (by Canon and many users) right up until several months later when suddenly it wasn't.

A summary of my 40D AF performance:

AI Servo mode on stationary subjects leads to a very low keeper rate. Mis-focused images are too frequent within a burst and focus takes way too long to recover. It should be right far more than it is wrong. It should not stay misfocused one side of the target (in front or behind) for one second at a time if the system is supposedly able to track subjects accurately at 6.5 frames per second.

AI Servo mode and One Shot mode with just the central sensor active can all too easily focus on the wrong thing as if the AF sensor is way bigger than it ought to be. Not just a little bigger than the AF sensor indicator (as for most cameras) but reaching half of the way to the next sensor. That is why I suspect those long vertical massive-defocus AF sensor elements that seem to link the upper, middle and botton AF sensors. [note: a sensor should not reach half way to the next sensor on a 9-point system, because that would imply a very low focus selectivity and an inability to handle small subjects]

The camera does not like focusing on relatively small targets. Again it is as if the central AF sensor is too big. No such problem observed on my 20D.

My AF problems are not specific to any one or two lenses and I have used some decent lenses that work very nicely with other cameras.

- Alan

Dec 09, 2007 at 02:39 AM

BogongBreeze
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p.1 #10 · 40D single AF point performance

The 40D I have is incredibly fast and accurate with all AF points and in all modes (AI Servo, one shot and AI Focus). It's very good in low light as well.

I believe the AA filter is a tad stronger on the 40D, but having said that, many of my shots are as sharp as can be with only a small sharpening in the default setting in LR (most of my lenses are extremely sharp). Talking raw files of course, because the sharpening for jpeg is adjustable in camera.

Alan321 wrote:
AI Servo mode on stationary subjects leads to a very low keeper rate.

Alan, you've posted this *at length* a number of times. As the manual and others here have said, AI Servo is for moving subjects not stationery subjects.

I suggest you try it with one shot or even AI focus.

Dec 09, 2007 at 03:43 AM

Dawei Ye
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p.1 #11 · 40D single AF point performance

Alan I seem to have had a similar experience to you regarding focus difficulties with the 40D, I'm heading into Canon Melbourne tomorrow to see what they say about it.

The 40D has really disappointed me so far, my 400D has always been flawless in it's operations, no lockups, not a single err99, tack sharp images, good high ISO performance, accurate autofocus, yet it has often been maligned as a novice camera, and the 40D praised to no end.

Dec 09, 2007 at 03:50 AM

Daan B
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p.1 #12 · 40D single AF point performance

Wow, replies about the 40D AF seem to be on either side of the extreme (very good versus not so good). That doesn't sound all that reliable to me.

I have experimented a bit with the focus recompose technique on my 5D, and I think I'll be using that in favor of the one AF point technique for a while. It seems more reliable. Even with wider apertures it works sufficiently. In some situations it is also faster to recompose than to search for the right AF point manually. I've missed some shots while turning the wheel.

It seems for real AF improvement I have to look at the 1D series. Well, maybe next year...

Dec 09, 2007 at 08:15 AM

Ola H.
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p.1 #13 · 40D single AF point performance

BogongBreeze wrote:
As the manual and others here have said, AI Servo is for moving subjects not stationery subjects.

But even for portraits, the subject is not always FULLY stationary. When I shoot kids for exemple there is no way One Shoot will do, at least not when using shallow DOF. The only way of nailing AF in these situation is the compose the pic and choose the "right" AF point and they use servo.

My 1DII this nails this practically EVERY time as long as you do your part as a photographer. I have no experience with the 40D and I don't think you can hope for as good an AF system as the pro models have, but I'm still with Alan here. A new camera like the 40D should be able to handle off center servo AF shooting in those "semi static" situations described above.

Dec 09, 2007 at 09:07 AM

Daan B
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p.1 #14 · 40D single AF point performance

Ola H. wrote:
But even for portraits, the subject is not always FULLY stationary. When I shoot kids for exemple there is no way One Shoot will do, at least not when using shallow DOF. The only way of nailing AF in these situation is the compose the pic and choose the "right" AF point and they use servo.

That was my assumption as well... But I found that, especially with moving subjects like kids and teenagers, composing and choosing the matching AF point took too long (on a 5D). I am having great difficulty using the joy stick for selecting an AF point - it seems to have a mind of his own. So I've used the wheel. But then you have to run through all the AF points before you can select the right one. Takes too much time... A solution could be to use a smaller aperture in these cases and still do the focus recompose technique (and hoping and praying that focus will turn out right).

BTW With my 5D I have no difficulty using AI servo (or AI focus) on semi stationary objects. But obviously in these cases focus recompose will not work. And I can't trust the outer AF points enough. So what to do?

Dec 09, 2007 at 09:23 AM

Alan321
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p.1 #15 · 40D single AF point performance

BogongBreeze wrote:
Alan, you've posted this *at length* a number of times. As the manual and others here have said, AI Servo is for moving subjects not stationery subjects.

I suggest you try it with one shot or even AI focus.

You're right. I'd hate for everyone to forget or miss my displeasure with a defective Canon product that they reckon is OK. There are plenty of other people who report great success with their 40D (rightly so) but some do it as if all 40Ds are perfect and that anyone who disagrees obviously can't use a camera.

I have used AI Servo and One Shot for stationary and moving subjects. All combinations have been problematic. AI Focus can be even more problematic because of the delay in change-over to focus tracking and the lack of control in timing of the change-over.

There is absolutely no technical justification in principle for AI Servo to mess up focus of a stationary subject for an extended time unless I am walking while I shoot. A small motion on my part may reasonably be interpreted as a subject motion but if I am trying to stand still then the motion should balance out and the camera should never take six frames to get back into focus, wouldn't you agree ? Not even two frames in a row should be off focus for a fast camera such as a 40D.

My point is NOT that all 40Ds are crappy. Just that mine is and that therefore some others may be. If it never gets mentioned and known about in the 40D community then you can be sure that it will never be fixed.

Shops here is Australia do not offer satisfaction money back guarantees. They will only repair faulty goods and replace faulty goods that cannot be repaired. If Canon says it is ok then there can be no refund. Our resale market is crappy too - I expect to lose 20% immediately and 30-50% soon afterwards. US shoppers are spoiled in comparison. If I buy mail order from the USA then I do not get local warranty support and I have to pay expensive freight both ways for purchase, service or return. So all things considered I think it is fair and reasonable to expect that the much improved AF system on my new 40D actually worked when I bought it.

I believe my reporting is unbiased but I do apologise to those who are sick of hearing it. One day when I am not so angry abut getting a third defective Canon DSLR in a row I will get sick of telling it

The trouble is that not everyone who may benefit from my tale has heard it and nor will they if I let it rest completely. As an indication that I am balanced about reporting these things I also repeat that my 1D2 and my 1Ds2 were really crappy at AF when I got them and that they now work very well after Canon recognised the defects successfully fixed them. I don't just tell the bad points.

- Alan

Dec 09, 2007 at 08:43 PM

Alan321
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p.1 #16 · 40D single AF point performance

Dawei Ye wrote:
Alan I seem to have had a similar experience to you regarding focus difficulties with the 40D, I'm heading into Canon Melbourne tomorrow to see what they say about it.

The 40D has really disappointed me so far, my 400D has always been flawless in it's operations, no lockups, not a single err99, tack sharp images, good high ISO performance, accurate autofocus, yet it has often been maligned as a novice camera, and the 40D praised to no end.

Dawei, that's bad news for you but please let me know what Canon say about it and what they do about it. If they fix it then ask for details of what was wrong. I was not allowed to talk with a technician when mine was sent to Sydney, and there are none here in Perth. I'm 2,500 miles from the nearest Canon technician and there's a receptionist between us

cheers,

- Alan

Dec 09, 2007 at 08:48 PM

Ola H.
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p.1 #17 · 40D single AF point performance

Daan B wrote:
That was my assumption as well... But I found that, especially with moving subjects like kids and teenagers, composing and choosing the matching AF point took too long (on a 5D).

Usually, I kind of make a preliminary composition in my mind - like where do I want the eye in this shot. Then I choose the focus point and then take a series of pics. When the situation changes I may have to change focus points, but I gather that goes rather fast and I do it without taking the camera from away my eye (but thats on an 1DII, maybe its faster to maneuver).

Dec 09, 2007 at 09:27 PM

therock
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p.1 #18 · 40D single AF point performance

Center AF sensor too big?

I just started testing today because I have experienced jumping to a different object than intended when using the center AF only.
So after reading the above I went to another AF point and it's looking better. Picking a smaller item in a scene is much better. But, I have to shoot for a week or so, then reverse to really see. I am a noob so it could be I just need to be more familiar with the world of AF.
Maybe some others will join.
I will say if this is the case, unless Canon agrees and offers a fix, or improvement, I'm keeping the camera. I'll just learn to recompose or how to use the body to it's best. No way would I revert to the 20D.

Dec 10, 2007 at 12:16 AM

Alan321
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p.1 #19 · 40D single AF point performance

therock, be aware that focus-recompose can cause back-focus problems See this article:
;http://visual-vacations.com/Photography/focus-recompose_sucks.htm

I appreciate why you'd want to keep the 40D. Me too, unless a 5D2 comes along. If it was my only camera then I would replace it for a more reliable model but as oe of several cameras it remains keepable

I have not yet done sufficient testing with the outer AF sensors but it's on my to-do list. We use the centre one because it is supposed to be the best. If the centre sensor is too big then it will almost certainly be because of the defocus sensors and that may be readily fixed with a firmware change. By Canon, not by users.

- Alan

Dec 10, 2007 at 06:01 PM

Gochugogi
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p.1 #20 · 40D single AF point performance

I have both a 5D (18 months) and 40D (2.5 months) and mainly shoot landscapes, macro and small products. First, the AF systems of both cameras are excellent and blow the doors off my old 10D and 20D--night and day difference.

In most shooting I can't tell a diff between the 5D and 40D AF. Both are peppy and reliable under most conditions. However the 40D does begin to show it's cross sensor advantage when you manually select AF points in low light/low contrast. Oddly the 5D seems slightly faster under the same conditions, but misses more often. Not a huge diff but having all crosses is a real advantage. Using AF from a Speedlite is an easy solution if it's too dark to use outer points (with flash disabled). Otherwise you may have to resort to a slight tilt of the camera or locking on a point of contrast.

I've always preferred manually selecting AF points because lock AF-recompose often misses due to shallow DOF at close distances and/or large apertures. What I'd really like is the choice of selecting AF points with ECF. Loved it on my Elan 7NE and EOS 3. The joystick thingie is chunky and slow.

Dec 10, 2007 at 07:06 PM

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