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Old Jan 31, 2005, 8:47 PM   #11
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:?You would think that a 1600 dollar camera would have a little more information abailable on how it operates. I would guess that trying to catch flying birds represents the outside edge of what AI is supposed to actually do.

Looking at the manual the cam 1 usese the center point to auto focus and when it senses movement switches to AI Servo. I would assume that if we could keep the target on the center spot it would work well. The prob may be that we start at center tnen cover another point, move past that and hit another. Cam probably cant react that quickly. We are literally shotgunning the bird. My cam hunts less with only center spoit turned on.

Are you guys using evaluative metering or spot meterin? I am attempting to try spot to see what the net results are. I am hoping the spot metering will either allow or not allow the shot relative to camera focus. As it is now, my shots generally end up soft on incoming or outgoing shots and do better when I am following the bird fromthe side.

Looking at the manuel [booklet] it apoears we need to keep the bird within the center point or on a constant path in one direction through the focus points with not backtracking.

This doesn't really addresss erics point about changes in color density. I just read a magazine [digital camera or something like that] which indicated the problem just as eric stated it.If the camera sensess a change from light to dark, it will focuson the daker subject. [Unless, Iassume, the target is within the center focus point.]

Hopeyou guys will pick up on this and make adjustments, corrections or thoughts. I would love to get betterin flight shotson purpose, rather than just by chance.
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Old Feb 1, 2005, 3:29 PM   #12
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Ok... I know you guys were just waiting for me to throw my 2 cents in here! :P

I've have not been impressed with the results I get using AI Servo. I just assumed it was me... but now you got me thinking. I mean it's to the point were I'm starting to entertain the idea of moving up to a 1D MKII. Of course this would be followed by an extended stay in the Dog House since my wife points out that the 20D is just a month old.

My problem is I NEVER have a nice open sky for a background... I shoot indoor sports! I mean as bad of an idea as AI_Focus is I get better results using it than AI_Servo. It's sad I know... I'm going to start paying closer attention and track my results...
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Old Feb 1, 2005, 3:49 PM   #13
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If you check naturescapes.net, you will see that after using 20D for a while, most of the users are not happy with the AI servo performace. I know, you can't expect AI servo like on 1DMK2 but it seems 20D AI servo doesn't match 10D's. I have no first hand experice, just typing what I have been reading on other forums.
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Old Feb 1, 2005, 11:02 PM   #14
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I read that nature scapes thread awhile back. As I recall (hey, its late... my could be remembering wrong) the problem talked about there wasn't exactly as I described it. I seem to remember it was about it not tracking at all. In my case it does track... but then very confidently tracks the background.

I certainly don't expect it to be like any 1-series camera. But I really do believe it's worse than the 10D.

Golfer, what you describe with the animal going away/towards vs. side to side is exactly as I would expect. When it's flying towards or away from you it is quickly leaving the DOF and that must be detected (very quickly) and adjusted for. I wouldn't expect the 10D or 20D to do that well. Even the 1-series cameras don't do that well (it's the hardest situation.)

But side-to-side flight of something not going blazingly fast should be fine. It should be able to do that, and it does... when the contast with the background doesn't throw it for a loop.

Eric
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Old Feb 2, 2005, 1:54 PM   #15
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I'm just curious about the problem you guys are having, and check up the manuals on the 20D and 10D. This is very strange because both sections on the predictive AF are similar:

1. The cameras will look at the center AF point first and then use the others to do predictive focus when no AF point is selected (ie automatic mode)
2. With a manually selected AF point, the selected AF point will focus track the subject.

IMO this is not normal. The AF points are laid out differently, but they should work the same! :?
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Old Feb 2, 2005, 7:53 PM   #16
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NHL, wildman, eric, timmy: it appears what we may be dealing with is just a weakness of the 20d. I can't say if it is better or worse than the 10d or anything else. This is a wonderfully useful thread in as much as my goal and I assume yours is to know the strengths and weaknesses of our tools.

I really like my 20d, it is far and away better than the camera [s] I have had in the past and I don't think for a moment that I bought a 1D. Any thoughts or suggestions we can come up with to overcome the weaknesses is just profit to us. As for me, I am going to take some more shots as we have described and see what I can come up with. Obviously I want to share with my new found friends here. Thanks you eric for starting this thresd.


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Old Feb 2, 2005, 8:10 PM   #17
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From what I've read, the best way, if you can master it, is to shoot in one shot mode. This is sad, as it shouldn't be.. flight photographer is what AI Servo is made for. But I found that one shot didn't do wonky things with what it focused on.

The problem is that a moving subject moves out of DOF the instant the lock is achieved. So you have to get very good at two things.
Taking that picture when the focus is achieved.
Guessing when something interesting is going to happen and start the camera focusing by 1/2 pressing the shutter.

Personally, I don't think I can do it. At least I can't now. With what I shoot, it's next to impossible to guess when the bird is going to turn into the sun angle so you can start it focusing at the right time.

But I know some people who swear by shooting that way.

NHL,
When you say "...when no AF point is selected (ie automatic mode)" do you mean when all points are selected? Just being clear here....

Eric
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Old Feb 2, 2005, 8:15 PM   #18
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eric; thanks for your replay, I intend to try just as you have indicated to see what my cam does when it does from blue sky to landscape. I assume you don't have the 10d for a comparason. Thanks for reinforcing that fast incoming shots may end up short of focus.

NHL; not sure I understand your post on #2, I assume the manual [incomplete as it is] is saying that when I select a focus point, the cam will begin focus from that point and adjust as the target pases the next point. Is that what you are getting? If that is correct, would you share with me what you believe is not right with that? Thanks

eric; please not my previous post which where I read in "Digital Camera mag" that the 20d seems to have a problem with focus almost exactly as you described. This may be a problem we will have to live with in the 20d.:?
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Old Feb 2, 2005, 9:12 PM   #19
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Golfer wrote:
Quote:
... This may be a problem we will have to live with in the 20d.:? ...
I see there is some new firmware for the 1D mk2 and 1Ds mk2 that's supposed to improve AI Servo... perhaps someday there will an 20D firmware update to improve AI Servo in our 20D's... :idea:
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Old Feb 3, 2005, 8:15 AM   #20
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eric s wrote:
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NHL,
When you say "...when no AF point is selected (ie automatic mode)" do you mean when all points are selected? Just being clear here...
Yes - The camera is freed to use any AF points although the manual says it starts with the central one initially before moving to the others as the camera tracks the subject.

When one selects a specific AF point only that one is used to track the subject in AI-servo mode. On the 10D the AF elements are actually larger than the rectangles engraved in the viewfinder so if a subject of low-contrast is tracked against a high-contrast background and the subject do not cover the whole AF area (ie for example a bird which only overlaps the area inside the engraved rectangle) the area outside of the rectangle (ie the background) will be in focus instead - It's only electronic signal and the camera can't determine the differences between background and subject (it just thinks that the moving subject is bigger than it really is). I did not upgrade to the 20D yet, so I can't test this...

You can try with with your 28-135 IS USM (since it can get close-up): AI-servo on a foreground 'plain' flower petal and move the camera around, with the shutter 1/2 pressed, and see if it pick up the details in the background to determine the size of the AF sensor or if other AF points are used (which does not sound right at all!)
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