40D single AF point performance

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Archive 2007 · 40D single AF point performance

Lance Lee
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p.3 #1 · 40D single AF point performance

BarnDog wrote:

Actually shot #2 was taken @ 125/sec w/ a Canon 85mm prime f1.8.

Well, there you go. 85mm * 1.6 = 136, so you shouldn't use any shutter speed under 1/136 second to expect handholdability. 1/125 is pushing it, and in this case pushed it too far.

Dec 23, 2007 at 12:18 AM

Paul Yi
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p.3 #2 · 40D single AF point performance

Lance,
What is that formulas that you used?

Dec 23, 2007 at 01:25 AM

Peter Szuhai
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p.3 #3 · 40D single AF point performance

Thats the rule of thumb for handholdability. Your shutterspeed should be 1/focal lenght as a minimum for handholding the camera. You have to take in account the crop of the camera as well (1.6x).

Dec 23, 2007 at 03:08 AM

python2000
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p.3 #4 · 40D single AF point performance

I like the rule of thumb, but depending on how you take pictures it can vary significantly. With the proper technique of breathing and body positioning you can use slower speeds. If you are moving while shooting, you will need much faster shutter speeds. I wouldn't think that the difference between 1/125 and 1/140 would be a big enough difference to account for blur. But that shot is suspicious because it doesn't look like anything is in focus.

Dec 23, 2007 at 03:17 AM

John Ferguson
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p.3 #5 · 40D single AF point performance

1/125 is sufficient as a "reasonable expection of sharpness" for hand held only if your subject is perfectly still. I think the girl in the second shot might be moving enough to cause motion blur. I also think the 40D is softer than the 30D (mine was). My opinion after owning a 1DMKIII and 40D is that Canon DSLRs with the built in dust shaker take softer shots on occasion than those without the dust shaker ... possibly due to the sensor not being mounted as "solid" as those without the dust shaker. Doesn't always result in soft shots, but happened often enough to me without other explanation (mirror shake?) that I sold both and am getting sharper shots and am much happier after going back to a 5D. The 40D does a a better focus system tho ...

Dec 23, 2007 at 03:51 AM

Navyblue
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p.3 #6 · 40D single AF point performance

keithreeder wrote:
I have to say that initially the difference in how the 40D performed compared to my 30D had me wondering if I was going to be one of those poorly-focusing 40D owners that covered the forums in the first month or two after its release but - funny thing! - as I've used it more and more, it seems to have got better and better..!

I remembered the time when 10D is launched it was being touted as having superior AF to the D60.

When the 20D is out, the old 10D becomes "slow focusing".

I think it's little soon to dis the 40D, the 50D isn't out yet.

Dec 22, 2007 at 09:56 AM

thw2
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p.3 #7 · 40D single AF point performance

I remembered the time when 10D is launched it was being touted as having superior AF to the D60.
When the 20D is out, the old 10D becomes "slow focusing".
I think it's little soon to dis the 40D, the 50D isn't out yet.

That's rather cute. Astute observation.

I don't think the 20D/30D/40D/400D are that different in AF speed and accuracy.

Dec 22, 2007 at 10:07 AM

thw2
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p.3 #8 · 40D single AF point performance

Venus wrote:
Why not try Canon Singapore if you are in Perth ...

Precisely. Canon Australia, just like Pentax Australia, is staffed with ineffective technicians. I have only heard bad things about bad services there. In Australia, Nikon is the only sensible choice with a decent service center.

Dec 22, 2007 at 11:37 PM

BarnDog
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p.3 #9 · 40D single AF point performance

trenchmonkey wrote:
Nothing's in focus in the 2nd shot. Looks like an IS lens was used that didn't have time
to spool up or some serious camera shake going on.

Actually shot #2 was taken @ 125/sec w/ a Canon 85mm prime f1.8. This is not camera shake it is simply OOF. This is exactly what I have been troubled with. I have the camera set to give the audible signal focus when locked, used the center focus point and took the shot.

I also was under the assumption that if given a good contrast area the focus point would lock on the closer object. Shot #1 is an example of this. Shot # 3 is an example where this doe not hold true.

I know this could be a problem with only my camera and I am not trying to add to this post with a "sky is falling" reaction. I am simply showing that I found similar occurences to the OP.

I look through my pics and am disturbed when I have missed a shot due to missed focus. I do this enough without gear anomalies adding to it.

Since posting here, I shot a kids Christmas music ensemble with my 30D under much the same conditions as the shots I posted. I did not notice a single "anomaly"

Dec 22, 2007 at 11:13 PM

treebeard
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p.3 #10 · 40D single AF point performance

Are you guys actually saying that there is nothing wrong with the second shot? From what I can tell the image is absolutely out of focus for no reason other than the camera had no idea what to focus on. While I admit my "technique" needs work, especially now that I am using Canon gear, I think the OP has valid points that I completely agree with.

Dec 22, 2007 at 01:25 PM

Alan321
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p.3 #11 · 40D single AF point performance

Mike Lucas wrote:
With the last one at least, it's clear what went wrong - as has been noted many times, the focus sensors are bigger than the red boxes. Here the camera focused on teacher's leg (or perhaps the floorboard?) instead of the boy's sweatshirt. Higher contrast - the focus jumps. As expected.

I don't have a convenient explanation for the second shot however - that one baffles me.

It's not as clear to me. Sure your explanation could be right but the child's shoulder is hardly a low-contrast edge and being closer to the camera the AF system should reasonably have focused on it. I've had such errors happen even after the system had already been focused on the closer subject for a few frames.

Successful AF is about a useful combination of greatest contrast and closest distance. Not just one or the other.

I've also had examples such as that second image and it has happened even though the camera is still being held steady with IS on and after it has already been focused on the subject (by which I'm implying no IS start-up issues).

- Alan

Dec 22, 2007 at 04:08 PM

Alan321
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p.3 #12 · 40D single AF point performance

jkurkjia wrote:
There must be a lot of unit-to-unit variation because my copy (and that of another 40D owner I know) feel very responsive and consistently nail the subject (moving ducks and a variety of stationary objects as well). I'm guessing you have a bad one; it happens but knowing it happens doesn't make anybody feel any better. If it isn't too late for an exchange I'd send the body to Canon.

Regards,

Joe Kurkjian

Joe, it's already been to Canon for a month and it came back unchanged. And as I think I said earlier, here in the Australian market we don't get the benefit of user-satisfaction returns. Unless Canon recognise that it is faulty then we are stuck with our purchase because the shop doesn't want to be stuck with it and probably cannot sell it again as a new camera.

I finally got fed up with my 40D and took the financial loss (about a third) by selling it. I feel better now. I have a clean concience about selling it because Canon confirmed it was ok. Whether I got a bad one or whether my perception of a good camera has simply been spoiled by having 1-series cameras I'm not sure, but I surely was not happy with the 40D in any operating mode. The bad finally outweighed the good as far as I was concerned.

If you have a good 40D then I am pleased for you and just a tad jealous but please accept that I know enough about using SLR cameras to recognise that mine was not as good as canon imply it is, pretty much like BarnDog's one. However, since Canon tested it and reckon it is within specs then I can only assume it is a generic issue with the somewhat loose standard of the 40Ds (or the technician was incompetent, which I doubt) in which some are far better than others.

For those who think I whinge too much about the 40D you may well be right but that will happen far less now that I've sold mine and it is not irritating me every day that I try to use it

I won't go so far as to recommend that nobody buy a 40D but I will recommend that nobody buy any new Canon model until after the early adopters have had it for a few months to give it a clean bill of health. At least then you'll have a chance to weigh up the chances of getting a dud, and it seems to me that whether it be the 1D3 or the 40D the chance is much higher than negligible.

cheers,
- Alan

Dec 22, 2007 at 03:56 PM

Venus
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p.3 #13 · 40D single AF point performance

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

Why not try Canon Singapore if you are in Perth ...

Dec 22, 2007 at 06:39 PM

jkurkjia
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p.3 #14 · 40D single AF point performance

Alan321 wrote:

If you have a good 40D then I am pleased for you and just a tad jealous but please accept that I know enough about using SLR cameras to recognise that mine was not as good as canon imply it is, pretty much like BarnDog's one.

I'm well aware there exist body-to-body variations and have zero doubt you can tell what will and will not work for you.

It bothers me that I'm forced to spend a few days testing new equipment before actually using it. My normal routine includes static AF testing, if okay move on to dynamic AF testing shooting constant velocity cars, if okay move on to field testing on know difficult dynamics targets, and finally, if the field test passes I can FINALLY use the camera.

Fortunately I don't shoot humans and normally shoot under conditions of good illumination and therefore don't test flash/camera performance; this is a real time-saver but I have no idea how many sins are buried in the camera because I haven't taken the time to check out the flash system.

IMO it is a real shame sufficient QC isn't designed into either the camera or factory test process and we customers have to do most of the work. Because of this I never buy gear from anybody without a good return/exchange policy that includes free round trip shipping.

I hope you have better luck on your next equipment purchase.

Regards,

Joe Kurkjian

Dec 22, 2007 at 06:59 PM

Lance Lee
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p.3 #15 · 40D single AF point performance

treebeard wrote:
Are you guys actually saying that there is nothing wrong with the second shot? From what I can tell the image is absolutely out of focus for no reason other than the camera had no idea what to focus on. While I admit my "technique" needs work, especially now that I am using Canon gear, I think the OP has valid points that I completely agree with.

Oh, there is something wrong with shot number 2, but it is probably not the AF. As trenchmonkey said, is it probably too low shutter speed or maybe just plain camera shake. If nothing is in focus, it is probably not simply focusing at the wrong distance.

Dec 22, 2007 at 02:49 PM

trenchmonkey
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p.3 #16 · 40D single AF point performance

Nothing's in focus in the 2nd shot. Looks like an IS lens was used that didn't have time
to spool up or some serious camera shake going on.

Dec 22, 2007 at 01:36 PM

Lance Lee
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p.3 #17 · 40D single AF point performance

Dec 23, 2007 at 12:18 AM

Paul Yi
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p.3 #18 · 40D single AF point performance

Lance,
What is that formulas that you used?

Dec 23, 2007 at 01:25 AM

Peter Szuhai
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p.3 #19 · 40D single AF point performance

Thats the rule of thumb for handholdability. Your shutterspeed should be 1/focal lenght as a minimum for handholding the camera. You have to take in account the crop of the camera as well (1.6x).

Dec 23, 2007 at 03:08 AM

python2000
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p.3 #20 · 40D single AF point performance

Dec 23, 2007 at 03:17 AM

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