Hair mod­els for com­puter graph­ics con­sist of many curves rep­res­ent­ing in­di­vidu­al hair fibers. In cur­rent prac­tice these curves are gen­er­ated by ad hoc ran­dom pro­cesses, and in close-up views their ar­range­ment ap­pears plainly dif­fer­ent from real hair. To be­gin im­prov­ing this situ­ation, this pa­per presents a new meth­od for meas­ur­ing the de­tailed ar­range­ment of fibers in a hair as­sembly. Many mac­ro­pho­to­graphs with shal­low depth of field are taken of a sample of hair, sweep­ing the plane of fo­cus through the hair's volume. The shal­low depth of field helps isol­ate the fibers and re­duces oc­clu­sion. Sev­er­al sweeps are per­formed with the hair at dif­fer­ent ori­ent­a­tions, res­ult­ing in mul­tiple ob­ser­va­tions of most of the clearly vis­ible fibers. The im­ages are filtered to de­tect the fibers, and the res­ult­ing fea­ture data from all im­ages is used jointly in a hair grow­ing pro­cess to con­struct smooth curves along the ob­served fibers. Fi­nally, ad­di­tion­al hairs are gen­er­ated to fill in the un­seen volume in­side the hair. The meth­od is demon­strated on both straight and wavy hair, with res­ults suit­able for real­ist­ic close-up ren­der­ings. These mod­els provide the first views we know of in­to the 3D ar­range­ment of hair fibers in real hair as­sem­blies.