Fast action sports and aperture

Discussion in 'Sports Photography' started by greyhound rick, Sep 28, 2008.

  1. Hello everyone!

    Since Ive switched from my 50mm f/1.8 lens to my 85mm f/1.4 lens for nightime shooting at Phoenix Greyhound Park Ive noticed a couple of things.
    (I was shooting at f/2.0 to f/2.2 with my 50mm vs. f/1.6 now with my 85mm):


    1. I am getting less shots in focus
    2. The shots I get in focus are much better with the 85mm

    My question is......for this type of shooting (low light, up close, fast moving action) is the difference between shooting at 2.0-2.2 vs. 1.6 great enough to take my in focus percentage down from around 70% to 50% or do you think the focal length may have something to do with it also? (Maybe its operator error too, but I think my technique is actually better now than it was a few months back when I was using my 50mm).

    I really appreciate your time and expertise!

    thanks for listening,

    Rick
     
  2. hallkc

    hallkc

    303
    Apr 1, 2008
    French Camp, CA
    Rick,

    Based on the info you have provided, I am gonna guess that you are getting fewer photos in focus simply because you are using a larger aperture. The difference between f2.2 an f1.6 is pretty sizable when it comes to depth of field. Trying to catch the focus of fast moving objects at f 2.2 is hard enough... f 1.6 would be maddening. (Although as you said, the ones that are in focus would look better)
     
  3. The real question is whether you are not nailing the focus or whether the depth of field is so narrow at those extreme apertures that your photos seem out of focus.

    Two entirely different problems.

    Perhaps you might post up an "unsharp" images so we can see what your problem really is. You are shooting with relatively short glass at extreme apertures. I suspect that your problem is merely a depth of field issue (the greyhound or more importantly the eyes of the greyhound may be out of focus, but perhaps the ears or the nose or the tail are in focus?).

    Is anything in your problem image focused??

    If you want to test my theory, shoot with the lenses at about F8 or so and crank up the ISO very high to compensate for the low light. If you get a sharp image (but a super grainy one), your lens is fine and your problem is DOF.
     
  4. Great input, as usual!!, thanks to you both!

    Rick, I actually notice both.....some of my shots are just flat OOF, but many times, however, I do notice the greyhound behind in focus or a "part" of the racer in focus and part out....i.e., muzzle OOF but body in focus, so your obsevations are right on.

    I will post some of each type when I can and really look forward to your comments. (My 85mm is going to the camera shop tomorrow for a focus check).

    thanks!!:smile:

    Rick
     
  5. You might be able to save yourself some money. Before you take the lens into the shop, why not photograph a scene that has little depth to it and see if your lens is focusing.

    Take shots at various apertures from a tripod and observe the results. If you were to shoot a brick wall for example and it was in focus, you can assume your problem was DOF. If you shoot the brick wall (or a magazine cover taped to a wall) and the image is soft, it is the lens.
     
  6. I agree about Rick saving some time and money.

    He has already showed me some focus test charts that he has taken with the 85 1.4. According to the charts, his lens is unquestionably Front focusing. It looks rather severe.

    He must decide as to whether or not a)he trusts his own evaluation of the lens tests. b)confirm his tests, as you suggest perhaps by shooting another target c)If an acceptable in-camera AF Fine Tune can be applied that will adjust the problem.

    mike
     
  7. Rick, it's not only the f-stop which makes a difference in DOF, but it's the combination of f/2.2 at 50mm vs. f/1.6 at 85mm. A quick check of DOF calculator for a DX camera, shows that 50mm @ f/2.2 yields 4.4 feet of sharp focus depth, while 85mm @ f/1.6 yields a field of 1.06 feet at a subject distance of 20 feet. That's a 3.38 foot difference in depth of focus, or perhaps almost the length of a dog.

    Add to that, that neither lens is particularly fast focusing/tracking with the older AF-D design. We haven't seen the shots, but if they are like your others where the dogs are running toward you then neither lens is probably able to exactly track that movement, and the 3+ feet difference in sharp focus zone is probably more noticeable with the 85mm.

    As suggested, check the lens' front/back-focus on a stationary subject to ensure it's not a lens malfunction. But it's likely just the huge difference in depth of field you're seeing.
     
  8. thanks to everyone. Your input is truly respected by me!!

    I just took some test shots and it appears that the 85mm is focusing fine on stationary objects. The perplexing thing is that when I use the test chart (im pretty sure the test was performed properly) it shows severe front focus. Then I take the lens outside and shoot a fence or blades of grass and the DOF focus area seems equal.

    Then.....I take the lens to the greyhound track and I get back focusing on some of my shots!

    I think there are a few things that I need to address here:

    1. I need to get the lens checked by a shop. Im doing that tomorrow. I think they are going to do it for free again because they didnt charge me when they checked my 70-200. I purchased both lenses from them and am a good customer.

    2. Ive been told that sometimes in my shooting environment when the greyhounds are running right at me that the speed of the subject(s) and the camera to subject distance (short) are such that the camera just cant process the shot fast enough (thats why Ive inquired so much about the D3). I can tell you that MANY times when reviewing my images on my monitor I will get a focus point indicated (red rings) and the area that the focus point is directly on is OOF! Now....this happens with ALL of my lenses. So...with that said, I would assume that the professional sports photographer at Tempe Camera that told me the D300 just cant keep up might be right (??).

    Heres what he says is happening......I achieve focus on the subject, press the shutter button and image is recorded. He is saying that between the time the focus is achieved and the image is recorded the subject has moved, thus the camera says (with the focus rings during playback...they dont show up if the camera thinks the image is OOF) the subject is in focus but when you look at the image on the monitor it is OOF. Do you agree that this could be happening here?

    Another aspect to this is that when I use the "focus only" feature and the camera theoretically is not going to fire unless you have achieved focus...there are many times this is NOT true! Ive had a lot of people tell me that if I want to eliminate OOF shots that all I have to do is use the "focus only" feature and the problem is gone. Not true!! So...with that said, maybe it is possible that the lens is fine, the camera is fine and it just cant handle this type of shooting environment. Low light, fast moving race dogs and close to the action is a rough combination. Couple that with a non "S" lens and an aperture of f/1.6 and maybe I should be thankful to get 50%!!!

    thoughts?

    thanks to you all!!

    Rick
     

  9. Why don't you post some random stationary test shots on a tripod so we can look at them. Instead of focusing close up, as you would do with a chart, shoot about 10-20 feet away from the subject. Use Apertures from F1.4 to F2.

    This is the first time that I am hearing that the D300 cannot keep up with focus. Using C-AF, the camera is continually focusing. Are you taking your thumb off of the AF-ON button when firing? Even a non-AF-S lens, once locked and acquired focus, will hold the focus as does an AF-S lens. Not to say that focus acquisiiton could be difficult, and you may need to deploy different techniques, but I cannot fathom that with the D300...not to say that I could be wrong.

    I have, and I am certain that many on this forum have experienced a red focus indicator(on the computer monitor)sitting on an UN focused area. In your case it could be two things. Your lens is back or front focusing. Or, your extremely narrow DOF using too wide open Apertures, the camera is not able to focus properly in such a narrow area.

    The feature of 'Focus only' in C-AF on release of the shutter. If you are Front focusing, the camera is not acquiring focus where the red focus bracket indicator is showing.

    mike

    PS. The test charts you showed me show the 70-200 to be focusing OK. But the 85 1.4 not. Not to say that in real world shooting this is always 100% accurate. But the fact that one looked on the money, and one not, kinda suggests that the 85 could be off. Please show us more images.
     
  10. kiwi

    kiwi

    Jan 1, 2008
    Auckland, NZ
    I think like me, you're really in need of an AF-S 85 1.4, COME ON NIKON !!!

    By the way, not the first time also that I have heard that the D300 AF struggles a little with subjects coming straight at you fast. Not tested it myself, but, have heard whispers.
     
  11. Could be. It is a tough task.

    I think that one should definitely eliminate any other possible interference as spoken about. The one thing that cannot be eliminated though, is the tough lighting conditions that Rick is facing...an even tougher job considering the narrow DOF that he is shooting with.


    mike
     
  12. kiwi

    kiwi

    Jan 1, 2008
    Auckland, NZ
    Couldn't agree more Mike. The lens needs testing for sure, but elimate that and...

    I admire Rick's shooting a heck of a lot - I can't think of something tougher - and I think it's putting a real test on the gear for sure.
     
  13. Thanks again for the comments....

    I'll post some shots when I can. Thanks for offering to look at them! I appreciate it!!

    Im not taking my finger off of the AF-ON button while shooting.

    Shooting racing greyhounds in low light, close up and them flying by at 45 mph is a condition where I can guarantee you a D300 cant focus on the subject 100% of the time. Ive shot 10,000 shots of them and my friend who is a near pro, cant get much better than I do with his Canon 40D and 300 f/2.8 lens. I know it may sound hard to believe, but I think shooting these dogs is very difficult in the conditions we shoot in. Not to say that I cant get better, because I know I have a long way to go, but, Ive had pros here in Phoenix tell me that they would just "pre or zone focus" and not even try to pan in the turns!

    Im taking the 85mm in tomorrow to have it checked out by Tempe Camera.

    Darren, you are EXACTLY right! When the greyhounds are coming straight at the camera it is VERY difficult to pan and get focus. Id pre focus for that shot more often than not!

    take care,

    Rick
     
  14. SeanMartin

    SeanMartin

    330
    Sep 24, 2008
    Watkins, CO
    Perhaps this has been covered, but Nikon built in compensation for front or back focusing in the D300. It's called AF fine tune under the setup menu. If you think the lens is front or back focusing, make the adjustments under AF fine tune and test.

    As indicated, you've dramatically reduced your depth of field making your job harder. Increasing focal length reduces depth of field. Opening your aperature reduces depth of field too. By changing your lens, you've made the job of focusing much more difficult. You've probably improved your sellability by getting closer though. It's a balancing act.