Perceptual Drawings VS Conceptual Drawings

I am too confuse about perceptual and conceptual drawings because I am believing there is always a story/meaning for every arts no matter perceptual or conceptual. Even it is like a simple perceptual art, I will also asking myself what is the story/meaning behind. That's why I am here to search some information to make myself clear about perceptual and conceptual.

Perceptual:

• Sensory.
• Create primarily for the sensation of the eye.
• Depicts the subject - matter realistically (like a photograph or snapshot in time). 

EXAMPLE:

Conceptual:

• Thought.
• Depicts the subject more symbolically / abstractly and conveys a concept or idea.
• Planning and decisions are made beforehand and the execution is a perfunctory affair.
• Less dependent on expression of skill by artist and "simply' execute by a craftsman.  

 EXAMPLE: 

SELF-EVALUATION: From the part of searching information and example of perceptual and conceptual drawings, I am finally figure it out the differences between perceptual and conceptual drawings and I am no longer confuse about it. I am searching different websites to compare the different information they had post and figure out which is more reliable.

References 

- http://ego-alterego.com/2011/03/amazing-conceptual-drawings-slawek-gruca/#.TxjBgvmGDHy
- http://www.sparked.biz/2008/06/12/the-art-of-illusion/
- http://www.modernedition.com/art-articles/new-op-art/gilbert-hsiao-1.jpg
- http://www.math.twsu.edu/history/Topics/geometry.html
- http://www.e-flux.com/announcements/op-art/