ukcatfan
DIS Veteran
- Joined
- May 11, 2001
- Messages
- 5,271
What I would not do is waste money on very fast lenses. I've seen people suggesting F1.4 lenses and I have to disagree completely. I've shot with those lenses and you wouldn't be using it to capture a gymnastics even because the DOF when it is full open will be very shallow... you would likely end up with photos where her hand is in focus and her body or blurred out... a fast lens is great for trying to get shots that you can pose carefully, but not for something like a sporting event.
At most you might want a F2.8 lens.
No offense, but you don't know what you are talking about on this. You must be thinking about the DOF from your experience using the lens with the subject close to your camera. The DOF gets much larger when you are farther away from the subject. I doubt you would be allowed within 50 ft of the athletes at a competition and would likely be even farther away. Just for example, an 85mm at f/1.4 and the subject at 50 ft gives you a DOF of 6 ft. It does not leave much room for error on your focus spot, but this is an extreme situation. Most people do not use the lens wide open unless it is a must because no lens is the sharpest wide open. So given that, an 85mm at f/2 and the subject at 75 ft gives you a DOF of 19 ft. That even leaves room for error if you slightly miss the focus point.
http://www.dofmaster.com/dofjs.html

