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5 versus 8 fps, and the relationship to AF

Discussion in 'General Technical Discussion' started by Retief, Nov 28, 2005.

  1. I read a post by a Canon sports shooter the other day where he commented that when he set his camera down to 5fps from 8.5 he found that he had a significantly higher percentage of in-focus shots in sequence. One of his theories was that this may be, at least in part, due to the amount of processing that has to take place keeping the subject in focus and that at 8.5fps it wasn't always keeping up, especially in poor light conditions. He also commented that he did not find that he was missing peak action any more often at 5fps than at 8fps. I have not yet tested this on my D2H, although I may give this a try Friday morning.

    This is of interest to me in general, and specifically as I will be acquiring a D200 shortly which will replace my D70 and I will be evaluating whether a second one will replace my D2H.

    Thoughts? Opinions? General comments and/or BS?
  2. fks


    Apr 30, 2005
    sf bay area
    hi bill-

    is canon's AF that bad :wink: ?

    it sounds probable. AF will only work if the mirror is down and the AF sensors are receiving light. if the shutter is up, then the AF is off. the higher your frame rate, the less time spent with the AF sensors receiving light, so the camera has to rely on the predictive capability of the AF system. if the subject's movement is erratic or not at a constant speed, then you'll end up with more OOF shots.

    i'd be interested in the results of your test as i've never really tried to track moving subjects with my D2H (other than panning shots).

  3. marc

    marc Guest

    there are really 2 issues

    1. is your subject moving erratically, and in what direction?
    2. is your subject moving but within a limited space, easier to track?

    if your subject is moving quickly from left to right or vice versa, are you able to keep up.

    if your subject is moving top to bottom, at what speed and are you able to keep up.

    do you use af-on, do you use lock on etc.

    many variables

    2. in shooting tennis, where subject has limited room to roam, or volleyball.
    you probably get more keepers, subject is easier to track
    3. football, soccer etc open field subject is harder to track

    the frame rate, may have something to do with keepers, but i think the shooters ability to keep the target in the viewfinder is more important.

    the camera is built to open and close shutter at the chosen speed, what slows it down is the ability of the shooter to keep up.

    one more point if in continuous high speed, if you are in shutter priority, the camera will give you whatever is there, focus or not, when you shoot.

    try using option 2, shutter+fps, slows down camera a little, but allows you to get framed and focused.

    i have shot high speed a number of times, all of the bad shots are usaually do to my inability to keep up.
  4. cwilt


    Apr 24, 2005
    Denver, CO
    I believe that viewfinder blackout time could be an indicator. The less time the viewfinder is black the more time the AF sensors are getting information. I have seen those numbers posted somewhere, but I can't remember where.
  5. marc

    marc Guest

    there is definitely some blackout time, on a d2h at 8fps is it noticeable , but very quick.

    if you are going to use the high speed fps option at full 8fps, you need to practice, you must know what you are trying to accomplish and you need to anticipate, and never take your eye off the viewfinder, always must track your subject,

    it requires some, practice.

    i did high speed waterskiing, and some extreme diving from dizzying height.

    following the skier was pretty easy, just pan in there direction.

    but try folowing a diver where they are moving from top to bottom

    much harder

    it is fun.
  6. I'll let you know, I am quite interested as well. Most of what I shoot, movement wise, is quite erratic. Holding a little-bitty-birdy in the focus point from 100 feet away can be a real pain, no matter what FPS you use. I am going to try this along with Close Focus to see how they both work, hope I don't end up with nothing but mush. With my luck this will completely kill that "one perfect shot" that would make me rich. At least that will be my NEW excuse.......
  7. Good points, Marc, and I can certainly tell you that the highest percentage of "bad shots" are absolutely, 100% operator error. The fun ones are when you have a player in perfect focus who is 10 yards behind the runner. I guess I could blame back-focus....:wink:

    Often times, especially with fast-moving birds, it is very hard to keep up. I have tried the mode that will only fire when in focus and have found my keeper rate much better without it. This may be as much frustration on my part, not hearing the shutter go when I tell it to, as to anything else. I have my focus set to the AF-On button on the back and not the shutter release as well which I find really helps when tracking moving objects.
  8. These are usually posted with the camera spec, and for the D2H/X it is a very short time. This posters thoughts was that it had as much to do with information processing as with physical aspects, I think they both may have something to do with it.
  9. petert053


    Nov 19, 2005
    Austin, TX
    Which Canon Camera?

    ...did he mention which Canon camera he was shooting with?
  10. fks


    Apr 30, 2005
    sf bay area
    hi peter-

    probably the 1DmkII because of the frame rate (8.5fps).


  11. eng45ine


    May 11, 2005
    Chicago, IL
    Some interesting thoughts here, I wish the high school football season was still going because I would like to switch to 5 fps from 8 fps and give it a try. I don't think that you would miss too much peak action by lower the fps in football and it would be worthwhile to see if there is a higher numbers of keepers with reduced blur. I'll be watching for your results Bill.
  12. Peter, as I recall I think ricky is correct, the 1DMkII.

    Frank, I agree, wish I had seen this a couple of months ago. If I can't figure it out via shooting birds, Lacross starts up fairly soon as well. Maybe I could even find some crazy people playing soccer or hockey......

    I'll let you know what I find on Friday, I am going to shoot Swans and will do some at each FPS rate.
  13. Bill I read an article that talked about this, I just can't remember where. They were saying it really depended on the lens that was being used. The faster AFS lenses should be able to keep up with the camera and let in enough light to acquire focus. On some slower lenses this may not be possible. I have found when shooting 8fs, my keeper rate does not change from when I don't shoot that fast. I seldom shoot that many pictures at one time. The Bob Heirman Reserve should be a great place to test with so many flying birds. I am going to test shooting there in manual mode and try your auto ISO as well.
  14. So, I planned on yesterday being my "test day" for 5fps vs. 8fps. One of my goals was to see if I would be "happy" with "only" 5fps regarding the D200 vs. the D2H. The second was to see if I could detect, subjectivly of course, if there was any quantitative and/or qualitative difference between the two frame rates. One concern I had was if I felt I would miss peak action any more oftion at 5fps.

    What I found was, I think, rather intersting. I did find that my in-focus rate was higher at 5fps than at 8fps. The strange part here is that I think at least part of that was auditory, it felt as if I was not following the birds as well at 8fps, which I think exacerbates any actual differences. When I was following well at 8fps, I think I saw a slight difference, but I do think the larger was caused by me. While not that much different, I think that the more sedate sound at 5fps calmed my nerves :smile: .

    You can see the two threads I posted in the Bird forum from last night as evidence of 5fps, I don't think this will be an issue for me. And while I "think" there "may" be a physical difference, I am SURE that there was a mental difference, at least for me.

    I also think, in retrospect, that one reason for more OOF at 8fps, is simply that more shots were taken. I did find, shooting the swans yesterday, that I filled the buffer a number of times at 5fps, something I very rarely if ever did at 8fps. I think this was due to my pushing it for the test.

    So, at the end of it, I think 5fps will suit me fine and I did not find anything that I can definitively point to that supports a camera-oriented difference in AF aquisition in the camera itself. Then again, this was anything but a scientifically controlled test, just my subjective observations.
  15. Bill I will try 5fps today, if we find the owls. Do you remember this summer when we were shooting the little green heron with the fish. Even with both of us using 8 fps, I had the fish in a different position than you. I really do not think it would make that much difference unless some incredible, fast action was taking place. The RR flip is one time the faster rate could matter. I would not go with the D2X over the D200 because of the difference. I think AFS is a bigger issue. Just my 2 cents. We will have lots of time to ponder this. I hope your new camera is in when you get back.
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