1. In CorelDRAW convert your bitmap / photo to Grayscale (Bitmaps > Mode > Grayscale (8-bit)).
2. With your photo selected, click the Edit Bitmap button on the Property Bar.
3. Run the High Pass filter.  (Effects > Sharpen > High Pass).

Use a high Percentage and Radius to bring out the subtle detail in the image.
The High Pass filter introduces more detail than the normal Threshold Conversion method.

4. Convert using:  Image > Convert to Black and White (1-bit) > Line art and adjust the slider until you are happy with the result.
5. Click on Finish Editing and return to CorelDRAW.
6. To convert to vectors, click on the Trace Bitmap button on the Property bar.

Tip provided by Richard Reilly, Graphic Designer and CorelDRAW Master.