10-03-2018 11:43 PM
The current October issue of Outdoor Photographer magazine has an excellent article on "Photographing Birds In Flight." That article contains two important recommendations, the first one of which I asked this Community about as a separate topic a month or so ago, and the second one which seems to be different than what Canon has documented in their literature relative to tracking a subject in AI Servo.
The first suggestion has to do with turning IS off (on the lens) when photographing birds, because, the article states, "it can slow down focus acquisition of the subject." As I recall the discussion on this point by this Community, that seemed not to be of concern and not necessary. Just wondering if anyone has any second thoughts on this point.
The second recommendation is to set the focus tracking sensitivity (think AF Cases, AF Configuration Tool) to the "slow setting" (which I believe Canon materials would present as a minus 2 setting for this parameter), because, as the article states, "(once you acquire focus, this keeps the camera from refocusing if the focus point slips off)." My question: the words "if the focus point slips off." Is this the same as failing to keep the subject covered by the AF pattern in use (e.g., 5-point Expansion in AI Servo)? This is an interesting, and potentially important concept. As I understand what the article's author has written, if Focus Tracking Sensitivity is set to its least active position (slowest responding position, akin to "locked in"), the AF system will not attempt to re-focus even if the subject has escaped the confines of (is no longer covered by) the AF pattern (or even the zone?) in use. This raises the question of the relationship between Focus Tracking Sensitivity control and AF pattern maintenance -- which overrides which, and how can they be made to "play nicely" together. Comments welcome, with thanks.
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10-04-2018 03:14 PM - edited 10-04-2018 03:14 PM
My experience is more with shooting soccer and "American rules" football but in my experience having IS active appears to slightly slow focus aquisition in lower light settings; this is shooting with a 1DX2 and a 300MM F2.8. I am using 1/1000 and 1/1250 shutter speeds with the lens wide open with the camera set to auto ISO with most low light shots either at 20K or 25.6K ISO to give you an idea of the light level. It may vary somewhat by lens and IS may not extract a penalty (or at least a noticeable penalty) in better lighting but this is my experience.
As to focus tracking sensitivity and AF point auto switching, although the standard settings for Case 4 are recommended for the sports I primarily shoot I prefer the operation with tracking sensitivity reduced one level to reduce OoF shots due to extreme erratic motion either by me or the subject. At its basic setting in Case 4 there is a more of a chance of losing desired focus either to something else (like an official) entering the frame or brief loss of subject in the active part of the array causing focus lock on something else. AF point auto switching sensitivity biases the system to more robustly track a rapidly moving subject that doesn't stay centered in the array (assuming you start with the center focus point being activated) while tracking sensitivity reduces the AF tendency to rapidly search for something else once the original subject has moved out of the selected AF point array. Even within a given photo situation no single setting is perfect for everything so you are playing the odds in choosing the setup that is best most of the time while still providing good performance in those non-optimal situations and fine tuning the system too much to a single environment (i.e. all sliders at extreme settings) will likely result in a setup that is sub-optimal much of the time.
The Canon AF supplement guide I used for the 1DX2 is very useful but once you understand the basics you will need to spend time shooting and making changes to optimize the system for the environment in which you take images. One of the more valuable uses of time for me was to spend some time at a couple of practice scrimmages (both soccer and U.S. football) to fine tune the settings AND my technique to get the best out of the system without having to worry about missing critical action. In the birding world I guess the equivalent would be find a flock of common gulls or crows depending upon where you live and try various settings to see what provides the best performance.
Sometimes technology makes life easier and sometimes it.adds more choices making life more complex. The Canon AF system is both and in its basic form it does a fine job but to use it to its full potential you need to do a deep dive into the system AND spend time trying different settings to see what works best for your photography.
10-04-2018 10:32 PM
Thanks very much, John. You actually gave me help in several areas at one time! I apppreciate being clued in to Dr. Hazeghi's materials and website -- I had never heard of him. He answered a couple of questions for me relative to what to expect in the way of AF speed based on camera body in use, including when using lens extenders -- even very practically providing information as to what works and does not work with certain classes of birds. In his excellent review of shooting with the Canon 400mm DO lens, he validated my field experience with my 7D2 when coupled with my Canon 300mm f/4 l IS lens and Canon 1.4 extender. He also supported my preference for handholding this combination. He provided his persepective, with reasons, for 2d image focusing priorities. He even includes a matrix of which AF Case he recommends for BIF situations, and how he tweaks each of the three parameters in each of the Cases. And, of course, provided his recommendation on use of IS for Birds In Flight (BIF). So, a goldmine and new source, which I really appreciate. If interested, please see my response to wq9NSC's comments on my inquiry -that gentleman had some really interesting things to offer, as well.
10-04-2018 11:04 PM
Thanks, Rodger. You offer much help and practical advice, which I appreciate. Just as an opener, I am blown away by your use of Auto ISO at ranges of 20K and 25.6K! Interesting information on several fronts (such as one photog's practical use of Auto ISO, and shooting at high shutter speeds in low light situations, for example).
Relative to Tracking Sensitivity (TS) and AF Point Switching (AFPS), if I understand you rightly, you and I are in agreement about what may be a potential (or at least theoretical) tug-of-war between these two parameters. It seems that when TS is set to a minus 2 (-2) and AFPS is set to a plus 2 (+2) in the same AF case, if their subject "disappears from the radar" (meaning is no longer covered by the AF pattern's points), TS will try its best to keep the subject in focus whille, at the same time, AFPS will be frantically looking at other AF points to try to lock on to what it thinks may be the wayward subject. This would seem to be an unwinnable head-butting exercise to be managed in realtime by the camera's AF firmware.
Your final advice seems highly apropos: "...you need to do a deep dive into the system AND spend time trying different settings to see what works best for your photography."
Canon's instruction manual for my 7D2 makes this fairly obvious when comparing pages 113 (TS) and 115 (AFPS).
It would be nice if Canon could provide their "school solution" to a question such as "what combinations of these three parameters, when used in a single Case, could be problematic and might lead to unpredictable and/or undesirable results" just as a heads-up for users of their gear. But, then, maybe that's where the deep dive comes in. I have written my own AF guide for personal use, but find I need to continue with its modification and updating as issues such as the ones in this email arise!
10-05-2018 06:22 AM - edited 10-05-2018 06:24 AM
Do you have this resource?
10-05-2018 08:12 AM
I absolutely agree with you that it would be nice if Canon offered a "school solution" that directly addresses questions like these. The AF supplemenatal manuals are useful but for situations like the one that you posed they don't provide a clear and concise directive.
There was a parallel situation with GM's current generation of Corvette which features a variety of driver modes (like Canon's AF cases) that are designed to maximize specific performance aspects under different conditions and like the Canon cases some of those sub-parameters are customizable under a performance traction management sub-menu. In addition other vehicle systems including stability control and the electronically controlled limited slip differential also interact as part of the overall system. The net result is very much like the AF system of a current DSLR where it is somewhat difficult for owners to get all of the possible performance out of the system. Fortunately for Corvette owners, the GM engineer in charge of developing and integrating these systems posted a thorough explanation of the intents and operations of the system along with a very detailed explanation of how the systems interact and a practical approach to customizing them for different track conditions. It would be great to have the same sort of information that shows up in the "Ask Tadge" forum (Tadge is the chief engineer for the Corvette platform) here in Canon land.
I would love to be able to shoot football at low ISO but the field lighting for high school football rarely allows that luxury so bumping up the ISO is a necessary evil. It allows you to keep the shutter speed at a reasonable level and to get shots that were virtually impossible back in the film days but it is still difficult for me to live with the high ISO shots compared to those few opportunities where natural light shooting is available. The first shot below is at ISO 16,000 and captures a critical stop to prevent a first down but the detail is clearly reduced as ISO is bumped up and the field lighting was a mix of mercury vapor and high pressure sodium which creates a challenging color cast. The second shot was taken under harsh daylight conditions where even the rubber filler for the turf is clearly defined as it is kicked up. AND it was a very fun experience for my 14 year old HS freshman daughter who carried an extra lens for me and also got a media and field pass to watch her high school team play during her first visit to Memorial stadium. The expense of that entertainment is a used 1DX is now on the way for her since that experience was sufficient to get her highly interested in photography and she plans to help shoot the junior varsity soccer team matches this Spring. She wanted to play with the JV soccer squad but the coach informed her that he isn't taking a chance with getting her injured in JV play since she will begin her HS soccer career as the primary varsity striker so at least she will get to photograph her JV level teammates.
For capturing birds in flight, having to go to a higher ISO with its associated loss of detail would be much less desirable than it is for sports action shots where much of the detail is already obscured by protective headgear.
10-05-2018 08:49 PM
Thanks once again, John. Yes, I've had this publication since it was originally issued in 2014 (and not updated in the last 4 years). It is a valuable resource, particularly if read along with the 7D2 owner's manual (which has been updated since its original issue). I have not found anything in the current issue of the owner's manual that conflicts with the 2014 AF-Setting Guidebook, or vice versa. Both documents are good, neither gives voice to the potential problems which may ensue when mixing possibly-conflicting values of the three AF Config Tool changeable parameters for each AF case, as documented in my response to Rodger (wq9nsc) yesterday. Your directing me to the AF-Setting Guidebook (Canon) and the website of Dr. Hazeghi have proven valuable.
10-05-2018 09:20 PM
Thanks for providing the continuing perspective, using the Corvette as an example. I hope that gives some readers an added impetus to seriously consider a 'vette! Your comments are relevant. I share your call for Canon to provide what GM does for its Corvette owners -- a pipeline directly to Canon engineers for answers to questions such as the ones currently under discussion. Camera owners who are interested in getting the best performance from their gear should be able to get accurate, reliable, understandable and complete responses to their questions from camera manufacturers. For many owners, the inability to get those kind of answers results in their having to do things such as developing their own documentation, some of which ends up being based on speculation, inferences, and possible misunderstandings. Providing semi-technical documentation for relatively-sophisticated camera gear must surely be a challenging, daunting task. Users should not have to be placed in a position of doing so on their own, based on incomplete available information. Enough said!
Nice football shots! Good luck to your daughter in her photography pursuit . She is fortunate in having a qualified
10-06-2018 08:56 AM - edited 10-06-2018 08:57 AM
Relative to Tracking Sensitivity (TS) and AF Point Switching (AFPS), if I understand you rightly, you and I are in agreement about what may be a potential (or at least theoretical) tug-of-war between these two parameters. It seems that when TS is set to a minus 2 (-2) and AFPS is set to a plus 2 (+2) in the same AF case, if their subject "disappears from the radar" (meaning is no longer covered by the AF pattern's points), TS will try its best to keep the subject in focus whille, at the same time, AFPS will be frantically looking at other AF points to try to lock on to what it thinks may be the wayward subject.
This would seem to be an unwinnable head-butting exercise to be managed in realtime by the camera's AF firmware.
I do not see it as a tug of war. I think you are giving the camera credit for too much smarts. It does [not] know one subject from another. IT is up to YOU to pick out a subject for it from all of the targets in the viewfinder. If you lose your subject, and then reacquire i a second latert, the camera does not know it is the same subject. It might, but I seriously doubt it.
So what happens when your subject drops off the radar with those settings. With TS set low, then the camera will be slower to refocus itself. Instead of immediately searching for a new target, it holds its’ current focus for a beat. With AFPS set high, then the camera should be ready to reacquire a target at your selected AF. Point. I think this behavior is similar to what would happen if you programmed a rear button for [AF-OFF] and pressed it for a moment, so that you can lock onto your subject again.