Low quality image for vector art portrait

[Hybrus]

Greetings guyz, I am currently doing a vector portrait,
Is there any possibilities to improve the quality of this image?
I just want to improve the details and I need to make the image more clearer
So when I posterize it in photoshop it will give me good results and details.
Hoping somebody out there can help me.
thank you in advance

 

[Tom Mann]

If, by "posterized", you mean something like this: http://cozmicone.deviantart.com/art/Alyssa-Milano-posterized-16979067

Then, I think you will find that you actually do not want too much detail. Instead, you want smooth transitions in lighting intensity as one goes across the face so that the contours are not jagged, and there aren't a lot of little islands of the next tonal value scattered throughout a different tonal value. The attached 2x2 composite will show you what I mean. The left column is "before posterization"; the right column "after posterization". The upper row is "sharpened", and the lower row is "softened". You decide.

Tom M

 

[IamSam]

The lower two images would be best for creating a vector painting/portrait in my opinion. Thanks Tom

 

[chrisdesign]

Here is a color version. (small size) As Tom mentioned, softened the image first.

 

[Hybrus]

thank you to your help, this is a lot of help, I really appreciated it, but the nose I have trouble making them haha . .
It was a years ago the last time I made something like this

 

[Tom Mann]

The reason the nose isn't quite what you expected is because because of the lighting, there is an almost perfectly straight, vertical line of demarcation between the brighter (viewer's) left side of the nose, and the darker (viewer's) right side of the nose. If you want the contours in your final posterized version to follow the shape of the nose, one way to do it is to artificially brighten the dark side, or darken the bright side so that both sides are about equal in brightness. If you do this before doing the posterization, there's a much better chance the contours in the posterized version will reflect the shape of the nose. You might have to experiment a bit with this to make it work the way you envision.

HTH,

Tom M