shooting fast action what aperature?

hey guys I shoot mostly snowmobiles and dirt bikes out in the backcountry, and I am slowly getting better shots all the time.
I shoot with a 7d mark ii canon 70-200 f4 is primarily. I never go below 1/800 and like to keep it at f8 if at all possible. I would love to be able to shoot at f4 but I have found in the past I will get the ski tip in focus but not the riders eyes and logo on his suit. Was this just a focus problem or is directly related to the dof setting at f4?

I will include the pic I am talking about first as well as a few more samples of what I've shot this season! looking forward to some critique!

now the first one was shot at 5.6 and the second at f8

bopper wrote in post #18298979
hey guys I shoot mostly snowmobiles and dirt bikes out in the backcountry, and I am slowly getting better shots all the time.
I shoot with a 7d mark ii canon 70-200 f4 is primarily. I never go below 1/800 and like to keep it at f8 if at all possible. I would love to be able to shoot at f4 but I have found in the past I will get the ski tip in focus but not the riders eyes and logo on his suit. Was this just a focus problem or is directly related to the dof setting at f4?

I will include the pic I am talking about first as well as a few more samples of what I've shot this season! looking forward to some critique!

What are you actually focusing on when you take the shot? His face, body or the snowmobile?

I typically use a single point manual select af in al servo so id start snapping on the sled I would say, this isn't a single shot it was one from a sequence.

bopper wrote in post #18298979
I never go below 1/800 and like to keep it at f8 if at all possible. I would love to be able to shoot at f4 but I have found in the past I will get the ski tip in focus but not the riders eyes and logo on his suit. Was this just a focus problem or is directly related to the dof setting at f4?

If you are getting the ski tip in focus, and not the rider, it is a focus problem as you should be focusing on the rider. If the focus is on the ski tip then you are wasting DOF as a significant part of it will be in front of the whole subject, you will only be using the part behind the focused distance. Focus on the rider and the sharpest part of the image will be the rider and the DOF will extend forwards and backwards to cover the rest of the snowmobile.

It is also related to the aperture of course, as a smaller aperture will give you more DOF and allow more leeway if your focus isn't bang on. You are shooting at a very low ISO, you could easily bump that to 800 and then shoot at f/8 without needing to compromise your shutter speeds.

thank you, yes ive finally started bumping the iso and trying to shoot around f8 for everything, although I want to venture back into shooting wide open and concentrating on my subject for the next few months of sunny riding, while saving f8 or higher for the ones with nice back drops

Exactly what sandpiper said.

Also, get familiar with your DOF at the various focal lengths of your lens in regard to the aperture you are using. Have a look at apps like Hyperfocal Pro or the like. They will help you understand your depth of field at differing focal lengths and apertures so you can better estimate the point of focus you will need to ensure you get the DOF you want. Once you get to know your lens, you'll start to have a lot more fun experimenting with aperture for artistic purposes, instead of just making sure you have enough DOF (or sufficient shutter speed, for that matter)

Oh, and nice shots, btw!

Nice pictures.

I shoot a lot of field sports (football, soccer, baseball, etc) and my default (also true for most others) is to have the lens wide open or very close to it. Mostly f2.8 or f3.2 in my case. At the distance away my subjects normally are, depth of field is small but enough to cover a person or two. The key is having the focus point on the part of the subject you want in focus. It is great if you can have it on the face but the torso is a bigger target, approximately on the same plane as the face, and more easily trackable. It takes practice but you can get better at it with enough experience.

Something that has not been mentioned directly is the distance to the subject. Using a DOF calculator like http://www.dofmaster.c​om/dofjs.html, check how distance can make a huge difference. At f/4, 200mm and 50 feet, your total DOF is about 2.9 feet. That would probably not be enough to get ski tips and face all in focus. Now change only distance to 75 feet and you get a total DOF of about 6.5 feet. Also, you should check/calibrate your camera/lens combination's auto focus using something like Lensalign (http://michaeltapesdes​ign.com/lensalign.html). You could be front focusing.