quick mk IV question

[John Chardine]

I was trying different C.Fn settings yesterday for autofocus and played with C.Fn III-8 AF expansion with selected point. I tried option 2 which expands the selected AF point to surrounding points if the manually selected point cannot focus.

My question is this- as the focus point shifts to surrounding points from the selected AF point, is the red oblong denoting the new focus point supposed to light up, i.e., the red oblong moves around the viewfinder? Mine didn't, i.e., the selected centre point continued to be lit. I'm pretty sure I wasn't tracking that well! And as far as I can see in DPP, the centre point was the only one ever used in any of the shots.

Any thoughts?

[Ed Cordes]

John, I have experienced the same thing. I have recently started using the expansion points around the center point. I have not seen the expansion points light up. My wife's 7D does light up the expansion points.

Will be interesting to see what others say.

[Charles Glatzer]

John,

I believe the illuminated AF point will only actively shift in the viewfinder when you use C.Fn III-8 #3 (45 points)

Chas

[LouBuonomo]

What Chas said... I experimented with it and only moves with 45 point... DPP will also show you which point with 45 but not with the other expansion points. At least not that I saw.

[Peter Hawrylyshyn]

John -
Another way to think of it is:
C.Fn III-8 AF expansion ( Option 2 - Surrounding AF point) enables the 6 AF points immediately around the AF point you selected to help in tracking the object . The selected AF point never changes, hence no change in illumination of AF point
C.Fn III-8 AF expansion ( Option 3 - 45 point area) enables the 18 AF points immediately above, below and beside the AF point you selected to help in tracking the object . If your selected AF point losses the object, the camera will switch to a new AF point and continue to do so (potential using all 45 points) to track the object and hence it shows you which AF point it is using

With both of these options you would also have had to set C.Fn III-4 AF Tracking Method to Option 1 : continuous AF track priority and also decided on your preferred AI Servo Tracking Sensitivity C.Fn III-2

I still haven't tracked enough BIF to decide which of these strategies is better - - would be curious what others have found

[John Chardine]

Many thanks to all so far. This has been very useful. I'm at a bit of a disadvantage in that the mk IV is my first pro body so I have all "that" to get used to plus the IV itself. Nice to know there are many BPNers who know a lot more about it than me!

[Malcolm Benn]

John, I know exactly where you're coming from .. my other camera is a 50D and the change is anything but subtle. I think Canon could have done a better job with the manual on this topic.

Peter, thanks for the explanation and it all makes sense except the necessity of setting C.Fn III-4 AF Tracking Method to Option 1 : continuous AF track priority.

[Axel Hildebrandt]

With both of these options you would also have had to set C.Fn III-4 AF Tracking Method to Option 1 : continuous AF track priority and also decided on your preferred AI Servo Tracking Sensitivity C.Fn III-2

I still haven't tracked enough BIF to decide which of these strategies is better - - would be curious what others have found

On the Mark III, I had C.Fn III-4 at 1, with the Mark IV it seems to work better at 0, at least for birds in flight.

[Peter Hawrylyshyn]

As i said, not enough BIF up here now to really fully evaluate C.Fn III-4

According to the Canon Mark 4 AutoFocus Guide - - with C.Fn III-4 set to 0 : Main Focus Point Priority the camera will switch subjects if a secondary subject other than the primary subject moves into the area of the manually selected AF point. When set to 1 , the camera is supposed to try and track your original primary subject and ignore the secondary subject (which to me would the priority for BIF). What is unclear in the guide is whether this just refers to subjects entering in the foreground, or would also apply if the selected AF point accidently drifted onto the background.

Axel - your BIF pic's with the Mk 4 have been very impressive. Is your suggestion referring to BIF primarily against the sky / water where you might momentarily loose AF , or also where the bird goes behind objects or against a very busy background?

Thanks
Peter

[Axel Hildebrandt]

As i said, not enough BIF up here now to really fully evaluate C.Fn III-4

According to the Canon Mark 4 AutoFocus Guide - - with C.Fn III-4 set to 0 : Main Focus Point Priority the camera will switch subjects if a secondary subject other than the primary subject moves into the area of the manually selected AF point. When set to 1 , the camera is supposed to try and track your original primary subject and ignore the secondary subject (which to me would the priority for BIF). What is unclear in the guide is whether this just refers to subjects entering in the foreground, or would also apply if the selected AF point accidently drifted onto the background.

Axel - your BIF pic's with the Mk 4 have been very impressive. Is your suggestion referring to BIF primarily against the sky / water where you might momentarily loose AF , or also where the bird goes behind objects or against a very busy background?

Thanks
Peter

So far my impression is that the AF performance is more reliable with III 4-0 regardless of background and objects/birds between camera and subject. I have the tracking sensitivity at 'intermediate slow' for now.

[Peter Hawrylyshyn]

Axel
That's very helpful and something i hope to test out at Sandy Hook in a couple of weeks

I think you said in an earlier thread you use C.Fn III-8 AF expansion ( Option 2). Is that because you've found it works better than (Option 3 - 45 points )?
Thanks
Peter

[Axel Hildebrandt]

Axel
That's very helpful and something i hope to test out at Sandy Hook in a couple of weeks

I think you said in an earlier thread you use C.Fn III-8 AF expansion ( Option 2). Is that because you've found it works better than (Option 3 - 45 points )?
Thanks
Peter

Yes, the camera is more likely to pick something contrasty in the background with 45 points. This was even more likely with the Mark III. With the Mark IV when you use central plus surrounding sensors it tracks really well even with a varying BG and the AF acquisition is quite fast.

[Mark Theriot]

A simliar question - when you have expansion set, should you see the expanding points in black (like you do on a 7D) or do they just not show up at all?

I notice nothing different in the viewfinder when I have III-8 set to "expansion".

Mark

[Axel Hildebrandt]

A simliar question - when you have expansion set, should you see the expanding points in black (like you do on a 7D) or do they just not show up at all?

I notice nothing different in the viewfinder when I have III-8 set to "expansion".

Mark

On my Mark IV, I have the setting that only shows the AF point once focus lock has been acquired. I don't think the surrounding points light up in this case.

[Ken Watkins]

No input from me as I have not had the oppurtunity to use mine yet, but I am most interested to see others recommendations.

[LouBuonomo]

Actually is you are in AI Servo they don't show movement.. In one shot they do.