Birds in Flight and AF Sensors

[Ian McHenry]

It is my understanding that the Canon 40D is the best value for money for catching BIF due to it's CMOS sensor and more recently the Olympus E3 with MOS sensor even faster @ AF.
I would like to know from more experienced bird photographers to what degree does the type of sensor determine their choice in a digital SLR.
With Thanks : Ian McHenry

[Robert O'Toole]

Nikon is the only manufacturer that offers professional level AF on prosumer (40D,D300) and pro (D3,MKIII) bodies.

The AF features and performance is one of the main reasons if not the chief reason many people including myself have chose to buy Nikon in 2007-2008.

The 40D AF is not in the same class as Nikon pro AF.
Nikon pro AF offers focus point confirmation in dynamic focus (for Canon users this means the AF point in use lights up in 45 point and Ai-servo)
N AF features 51 point AF all instantly selectable. N AF also uses RGB sensor input to lock focus.

The list goes on but I don't want to bore readers and sound like a Nikon Rep. :-)

I feel AF system performance is the most important reason to choose a DSLR body.

Sensor type doesnt have much to do with AF design or performance since they are different systems. I have owed 2 origional Canon EOS-1D cameras that used a CCD sensor and had great AF performance.

Robert

[James Shadle]

Ian,
Technique is much more important than the camera's sensor.
I have BIF images that I like and sell from a Nikon D100 / 80-400VR combo (the old stuff!)

Prefocus, prefocus, prefocus and don't for get the limiter switch!

[Peter Hawrylyshyn]

Robert -
I can't comment on Nikon, as i haven't switched - have stuck with Canon. I can however point out that AF performance is far more complex than just the number of AF points/sensors. It also involves the type of sensor ( + , vertical or horizontal), their layout, their resolution/accuracy, the lens speed ( f stop), camera software , speed of processor, ....

Although the Nikon pro AF has 51 sensors, only 15 are + type, while the 1D Mk3 has 19 + sensors and on the 40D, all 9 sensors are + sensors. More confusing with Canon is at which f stop , the + sensors will work. On the 5D, there were 3 + sensors active on lenses faster than f 2.8, yet on the 40D , the 9 + sensors are supposed to be active on all lens combinations faster than f5.6 (probably why it is so good at BIF with f4 lenses). Couldn't find any comparable info for Nikon.

The focus point confirmation for either system is only as good as the actual selected focus point. As described in the following thread discussing Canon AF performance, standard AF ( vertical or horizontal sensors) equates to anywhere within 1 DOF for the lens being used, while high precision + sensor should be within 1/3 DOF. For a 50mm f1.8 lens wide open, this can still randomly be anywhere within 4-6" . Again , no idea what tolerance there is with Nikon system. The thread also points out that the actual AF sensor zone can extend 2-3 x what you see in view finder, which can impact performance.
http://www.fredmiranda.com/forum/topic2/241524

Throw in operator experience/technique in handling large telephoto lenses during BIF .... was it the camera or the operator responsible for the blurred image?

From what i have read about Canon, 40D probably had best AF system for BIF using f4 - f5.6 lenses. WIth f2.8 lenses the 1D MK 3 series should be better as more + sensors will be active (19 versus 9) . Suspect the 50D will be better and faster than the 40D.

But as Artie said in a previous thread - proper technique will alwaysbe more important than the best/fanciest camera.

[Roger Clark]

To add a different method, here is what I do:

AI servo and track the subject. If, for example, the bird is far away, I'll track it all the way in to landing. I'll use the focus point the places the subject on the bird's eye and maintains the composition I want. Thus I rarely use the center AF point. I'm usually using a 1D Mark II and 500 f/4 on a tripod (with Wimberly), or sometimes hand held 300 mm f/4 or f/2.8. The 1D has the custom function set to high speed servo.

Roger
bird photos at: http://www.clarkvision.com/galleries/gallery.bird

[Maxis Gamez]

I've been recommended to use the center focusing point, too, and I've been doing that myself. One thing I've been wondering though is, when I use that center point, should I be using continuous-servo AF single point or continuous servo AF dynamic area mode. I'm using a D300 and if I use continuous-servo AF single point, I believe I am really using just one single focusing point (other D300 users could correct me if I'm wrong). But when I am using the center focusing point with dynamic area mode, then, although I still use the center point to focus, the camera actually could be using 9 or more points depending on my settings.

So when you say you use center focusing point only, does it mean you are using only one focusing point to track/focus the bird in continuous servo mode or, you are shooting in continuous servo.

you select the center focusing point to focus/track the bird, but the camera is using more than one point even though in your viewfinder, it is showing only one point is being used (I am guessing here cuz I'm not a Canon shooter)?

I hope I'm not confusing you...:o

Thanks !

I use the center focusing point for almost everything and for birds in flight I set my camera to AI Servo.

You are welcome!

[Robert O'Toole]

Hi Peter,

Long time no talk.

I can't comment on Nikon, as i haven't switched - have stuck with Canon. I can however point out that AF performance is far more complex than just the number of AF points/sensors. It also involves the type of sensor ( + , vertical or horizontal), their layout, their resolution/accuracy, the lens speed ( f stop), camera software , speed of processor, ....

Well I think you missed this line in my post: "The list goes on but I don't want to bore readers and sound like a Nikon Rep. :-)"
I didnt want to write a 6000 word essay comparing Nikon & Canon AF so I wanted to just point out some major differences.

Although the Nikon pro AF has 51 sensors, only 15 are + type, while the 1D Mk3 has 19 + sensors and on the 40D, all 9 sensors are + sensors. More confusing with Canon is at which f stop , the + sensors will work. On the 5D, there were 3 + sensors active on lenses faster than f 2.8, yet on the 40D , the 9 + sensors are supposed to be active on all lens combinations faster than f5.6 (probably why it is so good at BIF with f4 lenses). Couldn't find any comparable info for Nikon.

FYI Nikon cross sensors will work from F5.6 or better.

Honestly if you haven't used the new Nikon bodies you dont know what you are missing. :)
Nikon and Canon AF systems do not compare, even when you compare a Nikon prosumer and a pro Canon body.

The focus point confirmation for either system is only as good as the actual selected focus point.

My point was that Canon AF will not give you focus point confirmation in AFPS / Ai servo modes and Nikon does in prosumer and pro bodies.
This is a huge advantage in AF.

Throw in operator experience/technique in handling large telephoto lenses during BIF .... was it the camera or the operator responsible for the blurred image?

In my experience an OOF image is usually operator error :) I used to AF on BIF with my EF600/4 with a 1.4X + 2X often in good light.

From what i have read about Canon, 40D probably had best AF system for BIF using f4 - f5.6 lenses. WIth f2.8 lenses the 1D MK 3 series should be better as more + sensors will be active (19 versus 9) . Suspect the 50D will be better and faster than the 40D.

40D AF works fine, so does the MKIII, No complaints from me, but the both these cameras are in serious need of a redesign. I cannot believe Canon did not update the AF system with the 50D!!

The comparison could go on and on.

But as Artie said in a previous thread - proper technique will alwaysbe more important than the best/fanciest camera.

Of course this goes without saying, I have met folks in workshops with a brand new MKIII body that cannot even turn the camera on :eek:
I have also met people that use a Digital Rebel+tamron 1.4X+400F5.6 that can kill BIF and probably 90% of MKIII owners :D

Robert

[Robert O'Toole]

Desmond,

With Nikon AF I normally use Dynamic 3D and if the light level is too low or the subject too low in contrast then I go to single point and at that almost never center. I did this with Canon AF for 5-6 yrs with excellent results.

I've been recommended to use the center focusing point, too, and I've been doing that myself. One thing I've been wondering though is, when I use that center point, should I be using continuous-servo AF single point or continuous servo AF dynamic area mode. I'm using a D300 and if I use continuous-servo AF single point, I believe I am really using just one single focusing point (other D300 users could correct me if I'm wrong). But when I am using the center focusing point with dynamic area mode, then, although I still use the center point to focus, the camera actually could be using 9 or more points depending on my settings.

In single area continuous you re using just a single point in dynamic area you use the chosen point, center is default, then the AF will track the subject anywhere in the frame.

So when you say you use center focusing point only, does it mean you are using only one focusing point to track/focus the bird in continuous servo mode

yes.

or, you are shooting in continuous servo, you select the center focusing point to focus/track the bird, but the camera is using more than one point even though in your viewfinder, it is showing only one point is being used (I am guessing here cuz I'm not a Canon shooter)?

No this is called AFPS and Canon does not show you the AF point being used.

Hope this helps.

Robert

[Desmond Chan]

Robert,

Desmond,

With Nikon AF I normally use Dynamic 3D

That's the 3D 51-point 3D tracking? I experimented with it before by targeting a seagull flying across with a blue sky and some clouds in the background. I saw that focus point jumping around trying to keep track on the bird, so I wasn't sure if it was working right. I pressed the shutter button anyhow. And the photo showed it wasn't working right :D But probably my technique ( or the lack of it ) had something to do with the result, too.

I also read that the Dynamic 3D Tracking only works well when the target moves horizontally across the field and not going up and down, moving all over the place erratically. Would that match your experiences, too?

No this is called AFPS and Canon does not show you the AF point being used.

By "AFPS", are you referring to "AF point selection", as in selecting between 51 and 11 points in the case of the newer Nikons?

Thanks !


Desmond

[Maurice Allen]

Robert,

I agree that Canon should have addressed the AF issue with the update of the 50D. I really love my Canon 40D and don't plan on a switch to Nikon even though I was a Nikon film shooter back to the FM. A better move on their part should have been to leave the mega pixels alone or up it to 12 and work on the AF and get closer to the D300 specs.

[Doug Brown]

I don't think it's clear that AF hasn't been improved with the 50D. According to Brutus Ostling, the 50D has the best AF of any Canon digital body he's ever used. I've got one on order, and when I get it I'll file a full report on AF here.

[Robert O'Toole]

Robert,

That's the 3D 51-point 3D tracking?

I was referring to Dynamic AF.

Dynamic AF has 4 AF point options, 9 point, 21 point, 51 point and 51 point 3D.

I experimented with it before by targeting a seagull flying across with a blue sky and some clouds in the background. I saw that focus point jumping around trying to keep track on the bird, so I wasn't sure if it was working right. I pressed the shutter button anyhow. And the photo showed it wasn't working right :D But probably my technique ( or the lack of it ) had something to do with the result, too.

Usually in this situation you describe 3D should work well. I think in different conditions and with a little more practice and experience your results will improve.

I also read that the Dynamic 3D Tracking only works well when the target moves horizontally across the field and not going up and down, moving all over the place erratically. Would that match your experiences, too?

Not really, I have found 51 point+3D to work well even with birds flying towards the camera. But just like any AF system the results depend on the user, light level, contrast, and many other variables.
When 3D is having difficulty with low contrast subjects or low light I switch to single area AF.

By "AFPS", are you referring to "AF point selection", as in selecting between 51 and 11 points in the case of the newer Nikons?

Yes Canon AFPS is similar to Dynamic AF on Nikon. With either system you can choose the number of active points.

Robert

[Robert O'Toole]

Hi Doug,

I don't think it's clear that AF hasn't been improved with the 50D. According to Brutus Ostling, the 50D has the best AF of any Canon digital body he's ever used. I've got one on order, and when I get it I'll file a full report on AF here.

You are right no one is saying the 50D AF performance is not improved over the 40D.

Maurice and I were referring to comparing specs. Since the AF specs, 9-point TTL CMOS sensor, All points cross-type for lenses of F5.6 or faster, Center point additionally sensitive with lenses of F2.8 or faster, AF working range: -0.5 - 18 EV (at 23°C, ISO 100)
are identical between the 40D an 50D I think its safe to say that AF system specs on both Canon cameras are outclassed by newer cameras, especially my the new Nikon bodies.
Most Canon users I know and have spoken with are disappointed that the AF specs and features were not upgraded on the 50D although the 50D may AF maybe slightly better than the 40D.

Robert

[Roger Clark]

I put this article together to describe how I track action.

http://www.clarkvision.com/photoinfo...with.autofocus

Comments welcome.

Roger

[Marc Mol]

With Nikon AF I normally use Dynamic 3D and if the light level is too low or the subject too low in contrast then I go to single point and at that almost never center.

Hi Robert

When I use single point AF my point is always center. Why is it not for you?
Is there something wrong in doing this, can you please explain?

Cheers
Marc

[Robert O'Toole]

Hi Robert

When I use single point AF my point is always center. Why is it not for you?
Is there something wrong in doing this, can you please explain?

Cheers
Marc

Hi Marc,

Single point AF will work with any of the 51 points with D3,D700,D300 AF.

To give it a try just make sure the multi selector is on (not locked) and use your thumb to choose any AF point you would like.

Robert

[Marc Mol]

Thanks Robert

Makes perfect sense of course. I mostly use the selector in locked mode.

Cheers
Marc