Years ago I entered my first competition with an illumination. In my documentation, I wrote about using tracing paper to transfer the image. One judge commented on my lack. I still remember how down it made me feel. 

…there is good evidence that compositions of miniatures could be literally traced from one copy to another using carta lustra [tracing paper]…or could be duplicated by ‘pouncing’ in which the outlines of the original were pricked with rows of holes and placed over the new page and dabbed with a bag of colour, such as charcoal dust, to produce a dotted line. (p.57)

De Hamel also comments on it in The British Library Guide To Manuscript Illumination (p. 62) He believes there is tracing evidence as early as the 9th century, even having both the model and its copy.

James Farquahr in Creation and Imitation describes four tracing techniques used by 15th-century artists. They are: 

• Direct tracing, where a model is held to a glass with light passing through it, similar to a lightbox.
• Pressure tracing, where a page is placed under a master and a stylus is drug its lines leaving indentations on the copy.
• Moisture tracing, where the master’s lines are redrawn on the back and pressed to the copy.

With many tracing options recommended for budding artists in the Middle Ages, what is the best criteria to judge a scribe’s work today? 

My lightbox setup.

Today my scribal works are award scrolls. I use a combination of lightbox and free hand drawing. As a production scribe, the goal is to get a well done, period style scroll that relates to the recipient’s award and persona by the deadline.