rscheffler wrote:
Please keep in mind that later Stan reported that the IV he was using (it wasn't his) was set to 7 fps. At 10 fps you'll likely not get 40+ before hitting the buffer. From what others have reported you'll probably get 2-3 extra frames. But the buffer will clear very quickly.
Thanks for that update Ron. You saved me from buying an expensive new card and being disappointed. I've corrected by post.
I've been reading a canon document about the 1D4 AF tracking options and have reached a conclusion that needs to be tested. Perhaps one of you who does a whole lot more shooting than me can confirm this for me.
It seems to me that:
1. The AI Servo Tracking Sensitivity (C.Fn III-2) controls how quickly focus will shift to a background object. Does this mean not a foreground object ?
2. The AI Servo AF Tracking Method (C.Fn III-4) controls how quickly focus will shift to a foreground object. Continuous AF Track Priority sticks with the background object whereas Main Focus Point Priority will more readily switch to a foreground object. Does it really mean this or should it refer to the tracked object and another object ?
3. Therefore, I conclude that if you have set C.Fn III-4 to Main Focus Point Priority and if you have set C.Fn III-2 to one of the slow settings then there is a greater chance that the camera will lock onto a temporary foreground obstruction and stay there too long, causing lost shots. Anyone experienced this ?
I can see that getting these wrong could really mess with tracking a bird in flight or an individual sports person in a group.
It is written but not emphasized in the documentation that III-4 deals with foreground objects and III-2 deals with background objects. Therefore they can be complimentary or in conflict depending on how you set them. Or, it could be that each function actually deals with background and foreground objects vs the object being tracked, in which case the document is simply misleading.
The document I was reading is the "Canon EOS-1D Mark IV AI Servo AF Custom Function & ISO Speed Settings Guide". I got it from a link that was referenced somewhere here on FM but for the life of me I cannot find it now.
I'd welcome any feedback and/or a link to that file.
That's an interesting insight Alan, I'll have to study that. I had certainly never focused (so to speak) on the background/foreground distinction. If that's correct, then I can see how the CFIII-4 default might actually be better for my sloppy camera handling skills shooting sports. I often have more trouble getting the dot on the subject in the first place than I do keeping it there.
Nill Toulme wrote:
That's an interesting insight Alan, I'll have to study that. I had certainly never focused (so to speak) on the background/foreground distinction. If that's correct, then I can see how the CFIII-4 default might actually be better for my sloppy camera handling skills shooting sports. I often have more trouble getting the dot on the subject in the first place than I do keeping it there.
I could be wrong, but my interpretation is that, when Canon talks about "foreground" with regard to CF III 4, they literally mean foreground and are referring to objects closer to the camera than the intended subject. On the other hand, my interpretation is that, when they are using the term "background", they are not literally talking only about objects further away than the intended subject. Instead, I think that they are using "background" to mean anything other than the intended subject.
I am concluding as I am both from reading and from what I see when I use the camera. CF III 4 is designed for specific situations where an object other than the intended subject might get between the camera and the intended subject, and setting it at the "1" setting is supposed to keep focus on the intended subject and not switch to focusing on the intruding object. What I've found is that, except in that specific situation where something is likely to come between the camera and the intended subject, the AF system works noticeably better in most situations at the default "0" setting. With regard to tracking sensitivity and CF III 2, however, and the use of the term "background", I'm reasonably certain that they are talking about anything other than the intended subject, whether closer to or further away from the camera than the intended subject, and that is consistent with what I've seen from experimenting with CF III 2 settings with both the 1D Mark III and 1D Mark IV.
The following lenses have this feature:
EF 200mm f/2L IS USM
EF 300mm f/2.8L IS USM
EF 400mm f/2.8L IS USM
EF 400mm f/4 DO IS USM
EF 500mm f/4L IS USM
EF 600mm f/4L IS USM
EF 800mm f/5.6L IS USM
Some examples of situations in which Spot AF will be effective include staying focused on the eye of a helmeted driver in an open-cockpit racing car, capturing an athlete on a distant victory stand without using a telephoto lens ...
Maybe they too were thinking about a firmware upgrade for that feature? ;-)
Nill Toulme wrote:
Huh... it also appears that CFIII-4 has no effect one way or the other when AF expansion is not enabled? See page 26 of the AF guide.
Nill
There is no reason why CF III 4 should be dependent on how many focus points are active because with CF III 4 set to "1, it means, not only that the camera will delay in switching to a different focus point (if multiple focus points are active via CF III 8), but it could also mean delaying in changing the distance at which a single focus point is focusing and, thereby, ignoring an object that intrudes between the camera and the intended subject.
"The three important AF related Custom Functions introduced up to now, C.Fn III-2 Tracking Sensitivity, C.Fn III-4 Tracking Method, and C.Fn III-8 AF Point Expansion are associated such that each of their settings exert an influence on the workings of the other functions. For example, if AF point expansion is turned off, the AI Servo AF tracking method will not function."
See also the "Two types of AF tracking methods during area expansion" table on that same page.
While we're (sort of) on the topic — is there any difference between ROF and CFIII-8-3 other than that the former always starts with the center point, but with the latter you can start from a selected point other than the center? [EDIT: An answer to this question is found towards the end of the What's New in the EOS-1D Mark IV: Advanced Autofocus System document that Susi linked to above, under the heading "AF point expansion."]
Nill Toulme wrote:
It could, but apparently it does not:
"The three important AF related Custom Functions introduced up to now, C.Fn III-2 Tracking Sensitivity, C.Fn III-4 Tracking Method, and C.Fn III-8 AF Point Expansion are associated such that each of their settings exert an influence on the workings of the other functions. For example, if AF point expansion is turned off, the AI Servo AF tracking method will not function."
See also the "Two types of AF tracking methods during area expansion" table on that same page.
While we're (sort of) on the topic — is there any difference between ROF and CFIII-8-3 other than that the former always starts with the center point, but with the latter you can start from a selected point other than the center?
I'm not sure that the language in the first paragraph of what you quoted is quite accurate. I believe that, if expansion is turned off (via CF III 8), the method of tracking (CF III 4) is altered (in the way that I explained above), but I don't think it is disabled/not functioning.
Practically speaking, I think that the difference between using all 45 points and using area focus via CF III 8 is that you can start with a manually selected point with area focus, but you must start with the center point with auto selection. However, theoretically, with area focus, at any given instant there is a cluster of only 18 focus points available for use, but, from one moment to the next, that cluster can shift to a different group of 18 available points. So, theoretically, if the subject shifted, say, from a far left focus point to a far right focus point in an instant, that far right focus point might not be active. Practically speaking, I'm not sure how often that is likely to happen and that the actual operation is such that all 45 points are similarly available in either mode. In any case, I've never been a fan of auto selection of focus points, and I don't see myself using either auto selection or area focus very often. On the other hand, I've been very positively impressed with how well expansion to surrounding points works and how reluctant the camera is to be fooled by even a busy background with expansion to surrounding points.
Nill Toulme wrote:
I need to experiment some with these settings. See also the reference/link I added above.
Nill
I'm not sure that the engineers who design the systems or the technical writers who write the technical documents are always expert in knowing how those designs translate into real world usage. My theory is that it is up to the user to gain experience in knowing what settings will and will not work in various situations, and what works and what doesn't is also dependent on the style/technique of the shooter.
In any case, unless I'm missing something, the reference that you linked is, I think, consistent with what I said about the relationship between CF III 4 and CF III 8. When it says "C.Fn III-8-1, III-8-2, or III-8-3 must be on for C.Fn III-4 [AI Servo AF tracking method] to become fully effective", I think that means that, with expansion enabled, CF III 4-1 will delay both in switching focus points and also will delay in switching distance with a single point. If, however, expansion is disabled, only the second of those two things will occur.
Your reference also seems to confirm that the only real difference between auto selection and area focus is the ability, with area focus, to start with a point other than the center point. Again, though, I'd guess that, if the subject leaves the cluster, there might be a delay while the camera decides to use all 45 points to search for the subject. In practical terms, however, I'd be surprised if the difference between having all 45 points available and, at any moment, having the cluster of 18 available is anything but negligible.
Sure thing Dan, I have a question, when I set my camera to Peter Millers specs, my camera stopped focusing in auto.
I had to reset to default to get this to work again, anyone know why? Thanks ! ( I wouldn't think he would disable this option)
susi wrote:
Sure thing Dan, I have a question, when I set my camera to Peter Millers specs, my camera stopped focusing in auto.
I had to reset to default to get this to work again, anyone know why? Thanks ! ( I wouldn't think he would disable this option)
I'll bet he focuses with his thumb, and as with the mk3 & the mk4 that could be one of 2 of the back buttons.
