I'll give you a mini critique for each image if you'd like. If not, to late, I'm still doing it!
1. I like the canted angle and view point for this image. Looks nice and sharp with good highlights. It's let down by background, which is unavoidable. Looking at the light, if you shot away from the building, you'd be looking into the sun. To better blur backgrounds try a much larger aperture (1.4, 1.8 etc if you can). Nice image of a static car though.
2 & 3.Nice. Good panning with a perfect shutter speed. Nice amount of wheel and background blur. The sharp contrast between shadow and bright areas is annoying, but again, you've shot late afternoon on the eatsern side of the track, so shadows are going to happen. You could shoot from the western side of the track, but that late in the afternoon will produce very saturated colours, which you may also want to avoid. Try to learn the best times of day for each track you shoot, and where to shoot from. 2 seems a little sharper than 3. Nice images though.
4. This image is quite soft in the front of the half of the vehicle, 'A' pillar forward is too soft, but back from there is sharper. Seems your focal point was maybe mid car? Is this image cropped? If so, the crop is too tight, car images suit the car having somewhere for the car to 'drive into' if that makes sense. If it's not cropped, then your panning is good to follow a vehicle so tightly!
Hope you don't think I'm being a bastard by giving you such a critique, I just like motorsports!
Well done!
