what photoshop do need to convert photos to vectors? I want to convert pics of cars to vectors

As Nancy said, failure is more prevalent than success. Much depends upon the original image; lighting. composition and vantage point. On the other hand, in the days of film, making what Kodak called a tone-line conversion took over an hour, as I recall, and much depended upon the original image, as well.

First you made a density matching film positive from the negative, then sandwitched them together in register -- to cancel out the difference in tone -- film base to film base (which provided space between the emulsions).

Funky as it sounds, the next step was to place the films, with litho film as a bottom third layer on a turntable (an old record player) placed it at 45 degrees from a regular light bulb in the ceiling, turned on the record player and exposed the low-film-speed litho film. Develop the film in litho developer and you had a line conversion. A lot of work. But there was a joy that we don’t get in these digital days. On the other hand, maybe I am just old. The important things is that a bit of history provides valuable perspective.

Great tipp Norman!