thanks for all the replies, here is my summary of questions
1.washed out means?
2.all of those shots were under hard yellow lighting,which of my WB options would make it cooler?
3.i was kinda in a hurry taking those pics,(i guess i learned not too now,i was excited) Higher depth of field meaning higher F stop right? what would you guys recommend?
4) i have the standard and the nifty fifty lense. with this kind of photography, what lense/or tool should i need to get,to have better pictures?
thanks to all of you, youve all beeen helpfull
Washed out = over exposure. You camera settings were letting in too much light. You have to keep colors in mind when shooting. White objects that are the main focus of the shot can become easily overexposed if everything else is exposed properly. White is bright, this it what it does. Black can do the opposite. You can have under exposed blacks with all the other colors being the same. It's because White reflects all light and black absorbs. Also, if you meter off of black or white, it can throw the exposure off for the rest of the shot.
What type of light bulbs? Flourescent? Sodium? etc? I don't know what settings you have on your camera, but you have to match them to the lights. If they're standard parking lot lights, they're probably sodium, but that leaves an orange tint to them. The top photo almost looks green. Green is flourescent, but I doubt that's what you were shooting under. I could be wrong.
More DOF = higher f/ number. Shooting a single person, f/5.6 is decent. Shooting a group I usually use f/9-f/11. The car would probably be in that range as it's a larger object. Remember to shoot for effect though. You sometimes want a shallower depth of field and a wider aperture. Also, keep in mind that the distance from the object to the background can affect the blur. If you're shooting a car that's completely sideways from 10' away, the whole thing will most likely be completely in focus at f/11. If you shoot from the front of the car, getting a little of the rear sticking out, at 2' away with f/11, the rear of the car may be blurred a bit. It all has to do with distances and perspective.
The tough question. Want to do professional car photography? Buy three or four mono lights, appropriate accessories, the materials you need to bounce the light, and a wide angle lens, and have most of your lenses with at least a constant aperture of f/2.8. That's probably about $5000 or more.
best thing to do is start reading and decide which way you want to go. You can truthfully light a car with three or four speed lights and some cheap e-bay radio triggers (as long as they're working for you) and only spend $300ish. Your lens is fine. It's extremely sharp when stopped down and you have two feet to zoom with.
If you want to start learning a few things about light, try:
www.strobist.com
http://www.lighting-essentials.com/
http://www.joemcnally.com/blog/
Those are some good resources and there might only be one or two articles that pertain specifically to car lighting, but learning lighting in general will help you substantially.