I had an interesting experience shooting the Vintage Motorcycle Festival at Barber Motorsports park yesterday with my 45-200 lens. Earlier in the summer I was using the much smaller 45-150 panny lens for the Superbike races and while it wasn't the best lens I had used for motorcycle racing, the focus kept up reasonably well once I got used to it. I found I would like a little more reach so I sold the 45-150 and got the 45-200 I have now. Using it at the track yesterday was at first very disappointing. The lens would lock and then lose focus seemingly at random and was performing much worse than the small 45-150. I still got the shots I needed but was puzzled and was beginning to feel I had made mistake, however...
I went out again in the afternoon to my usual corner at the track and while I was waiting for the race to start, I was playing around with the lens and focus points to see if I could fine tune things. One thing I noticed gave me an "Ah HA!" moment. If one focuses on a spot and then zooms, the focus is lost for a moment and then the lens re-focuses. This happens with the finger off the shutter and whether or not you have Single or Continuous focus selected, neither of which should matter with the finger off the shutter.
This leads me to the conclusion that this particular lens is not a true "zoom" but rather a varifocal (or vari-focal) lens. A true "zoom" or design maintains the focus point (or pretty close anyway) as the focal length is changed or "zoomed". Discovering this helped me understand that I WAS the problem as I tend to zoom a bit when tracking motorcycles at races and I used to do this with my D200 and 80-200 2.8D without an issue. This meant I had to change my approach.
As I would track bikes around the turn in front of me I was leaving the zoom ring fixed until I turned back to catch the next pass. This made a huge difference and I imagine that with any lens, not zooming while tracking would give the AF system less to deal with but in this case it was a world of difference. The bonus is that many of the shots were very sharp and contrasty (for a lens at this price) and I feel a bit better than the 150 that is said by some sites to be a bit sharper. Maybe I have a good example but in either case once I met the lens halfway as it were, I was pleased with the results.
Some might suggest I get the 40-150 2.8 and I agree, if I had the budget right now I would have it (and the 12-40) but since I only need that serious firepower a couple of times a year for those events I don't think so (but I still want it). I plan on renting one next year so I can see if I MUST have it though.
Just FYI, here at the setting I used for the AF in case anyone is interested:
C-AF
Tracking Off
OIS on the lens, not the IBIS - seemed to maintain focus just a little better using lens OIS
Shot at continuous Low set for 4fps
9 box AF point size moved one click to the left of center
F6.3 at 1/800 ISO200 shot as jpeg
Full size jpeg can bee downloaded from here: www.jacksonphotoworks.com/images/VintFest2014_0488.jpg
I went out again in the afternoon to my usual corner at the track and while I was waiting for the race to start, I was playing around with the lens and focus points to see if I could fine tune things. One thing I noticed gave me an "Ah HA!" moment. If one focuses on a spot and then zooms, the focus is lost for a moment and then the lens re-focuses. This happens with the finger off the shutter and whether or not you have Single or Continuous focus selected, neither of which should matter with the finger off the shutter.
This leads me to the conclusion that this particular lens is not a true "zoom" but rather a varifocal (or vari-focal) lens. A true "zoom" or design maintains the focus point (or pretty close anyway) as the focal length is changed or "zoomed". Discovering this helped me understand that I WAS the problem as I tend to zoom a bit when tracking motorcycles at races and I used to do this with my D200 and 80-200 2.8D without an issue. This meant I had to change my approach.
As I would track bikes around the turn in front of me I was leaving the zoom ring fixed until I turned back to catch the next pass. This made a huge difference and I imagine that with any lens, not zooming while tracking would give the AF system less to deal with but in this case it was a world of difference. The bonus is that many of the shots were very sharp and contrasty (for a lens at this price) and I feel a bit better than the 150 that is said by some sites to be a bit sharper. Maybe I have a good example but in either case once I met the lens halfway as it were, I was pleased with the results.
Some might suggest I get the 40-150 2.8 and I agree, if I had the budget right now I would have it (and the 12-40) but since I only need that serious firepower a couple of times a year for those events I don't think so (but I still want it). I plan on renting one next year so I can see if I MUST have it though.
Just FYI, here at the setting I used for the AF in case anyone is interested:
C-AF
Tracking Off
OIS on the lens, not the IBIS - seemed to maintain focus just a little better using lens OIS
Shot at continuous Low set for 4fps
9 box AF point size moved one click to the left of center
F6.3 at 1/800 ISO200 shot as jpeg

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Full size jpeg can bee downloaded from here: www.jacksonphotoworks.com/images/VintFest2014_0488.jpg