Continuous focus tracking

Janice

Janice

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Janice
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How can a Canon, with only 9 autofocus points, autotrack a bird in flight for instance, by automatically going from one focus point to the next as the bird passes over them when there are so few focus points?

I can see how it works on a Nikon with 57 points, but I cant fathom the canon way.

Also, dont you think they should have caught up and had a few more by now? :shrug:
 
It predicts the speed of the bird and focuses accordingly.
 
Janice said:
Also, dont you think they should have caught up and had a few more by now? :shrug:
Click to expand...

Perhaps it's time to jump ship janice :D
 
Janice said:
Also, dont you think they should have caught up and had a few more by now? :shrug:
Click to expand...

A long time ago...the 1D2's have 45 focus points.

The other point to remember is that the AF region around the focus point is much larger than the small red symbol projected on to the focussing screen.

Bob
 
Janice said:
I can see how it works on a Nikon with 57 points, but I cant fathom the canon way.

Also, dont you think they should have caught up and had a few more by now? :shrug:
Click to expand...
You're comparing apples with oranges.

The Canon 1D-series has 45 AF points and probably does the same sort of job as the Nikon D3, which has 51 (not 57).

The Nikons which are most similar to your Canon 40D - the D80 and D90 - have 11 AF points.
 
Janice said:
How can a Canon, with only 9 autofocus points, autotrack a bird in flight for instance, by automatically going from one focus point to the next as the bird passes over them when there are so few focus points?

I can see how it works on a Nikon with 57 points, but I cant fathom the canon way.

Also, dont you think they should have caught up and had a few more by now? :shrug:
Click to expand...

It doesn't basically :lol: Thats one of the really annoying things about canon. They intentionally cripple their cheaper cameras with substandard AF.
Theres only one option for reliable AF with canon and thats their 1-Series.
Where as nikon seems to be quite generous with the AF in their cameras.
 
Canon Bob said:
The other point to remember is that the AF region around the focus point is much larger than the small red symbol projected on to the focussing screen.

Bob
Click to expand...


In conjunction to that fact ... As I only have five points on my D70, I use the AF lock buttons on the end of my 70-200 if i'm tracking a bird in flight ...it works for me like this:

Get initial focus... As the bird rushes from the view finder or my focus point, I instantly hold down the lock, allowing me to quickly find it again, then I'll let go of the lock, the AF quickly re-focuses ...etc etc.

In real use, it actually means I can quickly snap back to focus without the AF rushing around trying to find a subject, and maintain a good clear view in and around the distance that the bird was in...if you see what I mean.

You have those buttons on your 200mm I'm assuming btw.
 
Werecow said:
Thats one of the really annoying things about canon. They intentionally cripple their cheaper cameras with substandard AF.
Theres only one option for reliable AF with canon and thats their 1-Series.
Where as nikon seems to be quite generous with the AF in their cameras.
Click to expand...
???

I wasn't sure what you meant by this so I did some research.

Canon ... 1D/1Ds = 45 AF points, other bodies = 9 AF points
Nikon ... D3/D700/D300 = 51 AF points, other bodies = 11 AF points
Sony ... 11 AF points max, even on the A900
Pentax ... 11 AF points max
Olympus ... 11 AF points max

I was on the verge of proposing that there were probably engineering reasons for crop-sensor bodies only having 9 or 11 AF points as opposed to 40+ for full-frame bodies. After all, there's a lot less space to play with on the AF sensor. But then I discovered that the Nikon D300 has the same 51-point system as the D3. So I guess you have to ask, if Nikon can do that in a crop-sensor, why can't/won't Canon?
 
A lot of the time it's just bells & whistles really - I found that often I have to turn down the number of points I use as the amount of available points tend to confuse the camera (D300) whilst when I had my 5D focusing was very fast & accurate - you just have to have a good aim :p

I will say though that the 1Ds focusing system beats the socks off of my D300's every day of the week though! :(
 
I'm not really too up to speed on Nikon's methods but here goes;

Canon use phase detection for AF in their DSLR's (and most Nikon bodies do too). This is probably the safest and quickest method as focus direction can be computed before a move is made.
Many P&S bodies use contrast recognition for AF and this requires an initial move to ascertain which way the focus shift is. I believe that the D300 use contrast recognition for its additional points (unlike the D3)
If this is factually correct then the D300 (when using the additional points) has sacrificed speed inorder to get more points available.

I'm not knocking the system, just taking a shot at why it might be a feature.

Bob
 
Canon Bob said:
I'm not really too up to speed on Nikon's methods but here goes;

Canon use phase detection for AF in their DSLR's (and most Nikon bodies do too). This is probably the safest and quickest method as focus direction can be computed before a move is made.
Many P&S bodies use contrast recognition for AF and this requires an initial move to ascertain which way the focus shift is. I believe that the D300 use contrast recognition for its additional points (unlike the D3)
If this is factually correct then the D300 (when using the additional points) has sacrificed speed inorder to get more points available.

I'm not knocking the system, just taking a shot at why it might be a feature.

Bob
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looking at the manual the D300 uses Phase detection under normal use but switches to contrast detect autofocus in live view tripod mode.:shrug:
 
Yeh its infuriating. Also the fact that the centre point only performance of canon's lower models in Servo AF is massively inferior compared to the 1 series as well.
Its definitely a choice they've made to get you to spend more money on a 1-series :(

StewartR said:
???

I wasn't sure what you meant by this so I did some research.

Canon ... 1D/1Ds = 45 AF points, other bodies = 9 AF points
Nikon ... D3/D700/D300 = 51 AF points, other bodies = 11 AF points
Sony ... 11 AF points max, even on the A900
Pentax ... 11 AF points max
Olympus ... 11 AF points max

I was on the verge of proposing that there were probably engineering reasons for crop-sensor bodies only having 9 or 11 AF points as opposed to 40+ for full-frame bodies. After all, there's a lot less space to play with on the AF sensor. But then I discovered that the Nikon D300 has the same 51-point system as the D3. So I guess you have to ask, if Nikon can do that in a crop-sensor, why can't/won't Canon?
Click to expand...
 
Dogfish_magnet said:
looking at the manual the D300 uses Phase detection under normal use but switches to contrast detect autofocus in live view tripod mode.:shrug:
Click to expand...
I'm going to take a guess that the external points are always contrast detecting...it would be difficult to cram so many phase detection prisms onto a crop sensor.

Bob
 
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