Here is a more detailed breakdown for what each of the graphical settings do:
This options allows you to choose whether to have the game take up the whole screen to itself or to be in a window where you can also see other applications.
Lower resolutions will give you higher performance but lower visual detail.
This determines the choice of resolution. Normally you should stick to the native aspect ratio of your monitor or else the game will look squashed.
The rate at which you monitor redraws the screen. Normally you should stick to the native refresh rate of your monitor (LCD/LED are generally 60hz).
Use this option to set appropriate values for all the visual options based on the level you choose – Best performance, Better performance, Balanced, Better quality, Best quality and custom. This is the quick way to set a “sensible” set of values for the spec of PC you own. Once set, you can then further tweak the resultant values up or down, see how it effects performance versus visual quality.
If this is turned off, the game will run as fast as possible but there is chance you will see screen tearing. If this is turned on, the frame rate of the game will be limited to your refresh rate.
Ped Distance Culling
The distance at which pedestrians become visible in the game. Setting it higher costs in performance but lets you see peds further into the distance.
Turning this up will improve the detail and accuracy of the shadows in the game at the expense of performance.
Options for which cars produce shadows from their headlights. Turning this on will give a better visual experience, but a cost in performance.
Pretty coloured shadows are cast by translucent objects when this is turned on.
Turning this on makes everything look smoother and less jaggy.
Depth of Field (DOF)
De-emphasises objects in your peripheral vision.
Emphasises bright light sources.
Emulates shadowing of ambient light. It can be turned off to improve performance.
Particle Effect Quality
This affects the density and complexity of the special effects such as smoke, fire and gushing blood.
Car Reflection Quality
This affects the level of detail and update rate of the dynamic cube maps that are used to draw a reflection on shiny cars.
Use this control to adjust the level of detail on game objects such as PowerUps, pedestrians and anything breakable.
This setting will determine which cars produce skid marks, turning this on for more cars will cost performance.
Alters illumination conditions. Affects both the brightness and contrast. Light and dark tones are less affected than mid tones.